BGP AS_PATH Attribute

I've been working through the BGP section in the CCNP Lab Portfolio book over the past week. This morning I went over a short lab regarding the AS_PATH Attribute. It's kind of strange that the BGP labs have been the shortest labs so far, you would've thought BGP would of been a pretty big section.

As other people mentioned, this chapter has a lot of mistakes and it makes the configuration of the labs confusing. You don't know if it's you not configuring the routers right or the book giving the wrong information.

Even still I managed to get through this chapter which consisted of created a special BGP access list with the use of "regular expressions".

I configured the following regular expression access list on the ISP router:

ISP(config)#ip as-path access-list 1 deny ^100$
ISP(config)#ip as-path access-list 1 permit .*

ISP(config)#router bgp 300
ISP(config)#neighbor 172.24.1.18 filter-list 1 out

Tomorrow's BGP lab seems to be longer than the other labs so we'll see just how much material I'll have to work through. I shouldn't be able to finish a full BGP lab in 15 minutes...not yet anyways :)

DHCP Router Configuration

I spent this morning reviewing DHCP router configuration and the many options that you have as a DHCP server. From what I've seen in real networks most routers won't utilize DHCP configuration unless it's for a smaller network using a Cisco 1841 or something similar. The bigger enterprise routers are usually deployed in bigger environments where there are already dedicated DHCP server(s) in place. I did learn a command that would of helped me tremendously during my CCNA studies.

To all the people studying for the CCNA try out this command on a router and you'll get a nice surprise:

Router# show ip port-map

Yup that's right, you get a complete list of the most common TCP and UDP ports used, very handy for the CCNA exam or just for a quick reference!

IS-iS over Frame Relay

I knocked out the last of the IS IS topics in the CCNP Lab Portfolio finally. One interesting caveat about IS-IS and NBMA (Non-Broadcast Multi Access) networks is that it can only perform as point-to-point connections. Which is very different from OSPF that can use different NBMA technologies such as multi-point. Tomorrow I begin the different routing manipulation topics that's a HUGE part of the exam I hear.

CCNP Portfolio IS-IS Labs

I'm about half way through the CCNP lab portfolio book finally. I started on the first IS-IS lab presented in the book and it refreshed my memory on a lot of the IS-IS topics which I can honestly say that I forgot. The lab was focused on the basics and the end goal was to setup an IS-iS lab where the core network was running as an IS-IS level 2 network. The other goal was to implement security measures to prevent rouge outside networks/routers from trying to create an adjacency to the current IS-IS network which was pretty straight forward. I plan on completing the IS IS portion of this book within the next week or two, I'm working overtime at the NOC this upcoming week so we'll see how far will get by this time next week rolls around!

Finished the OSPF CCNP Portfolio Labs

All of this studying and labs (lots and lots of labs) are starting to pay off. I'm finally starting to grasp many of the CCNP routing topics without having to reference a book or look up how to configure certain commands. I went through the OSPF challenge lab and was able to knock it out in about 20 minutes which is pretty good. One thing about troubleshooting networks is that you can gain a lot of information just from looking at the running configurations and the ip routing table. Looking at the device log (show logging) helps you determine what happened and when, this is very helpful in real world environments. Next up is IS-IS and then the redistribution chapters which is gonna teach me a lot of new techniques I bet!

OSPF Over Frame Relay

Today worked through the CCNP Portfolio lab 3-4 which has to do with OSPF over frame relay. This lab was mostly review for though. I did finally bit the bullet and learn how to setup a Cisco router as a frame-relay switch finally. I always used the frame relay icon in GNS3 for all of my frame relay studies. It was fairly straight forward, just mainly pointing the DLCI's where they need to go and configuring the serial interfaces for frame DCE connections was all that was needed really. I also went through some of the different type of OSPF NBMA topologies you can configure, such as point-to-multipoint or creating neighbor connections through the OSPF configuration.

CCNP OSPF lab Portfolio

I finally finished up the EIGRP section and I'm now moving through some of the OSPF labs. Right now the labs are just going over basics but I have learned a few new things that I never thought about when it came to OSPF. When configuring loopbacks with IP addresses and using OSPF as your routing protocol, If their aren't any specific Router ID's (RID) set, OSPF will use the Loopback address as the RID.

For example if I configured the loopback 1 interface with the IP address 192.168.1.1 255.255.255.0, the router would use this as the RID as well. So when you run the show ip route command, it shows up as 192.168.1.1 /32 instead of the 192.168.1.1 /24 that you have actually configured on the lo1 interface. to circumvent this, you should type in the interface command ip ospf network point-to-point which tells the router to treat the loop back interface as routing destination rather than a routing ID.

Multicast Protocol Overview

Multicasting enables data to be sent over networks to a group of destinations in the most efficient way. The data is sent from the source as one stream; this single data stream travels through the network. Other network devices only replicate the data through the network if they have other members on their interfaces that are apart of this destination group.

Multicast groups are identified by Class D IP addresses, which are in the range from 224.0.0.0 to 239.255.255.255. Muticast uses the Internet Group Management Protocol (IGMP) and Cisco Group Management Protocol (CGMP) for determining which network devices require the multicast data stream. Protocol Independent Multicast (PIM) is used for determining the best way to route multicast traffic.

There are many differences between Multicast and Unicast packets. Unicast duplicates a packet for each reciever that it needs to send the data too (one copy for each reciver). Multicast sends one packet stream as mentioned previously, downstream routers replicate the packets only on links where receiving hosts exist. Multicast provides the following advantages over unicast:

• Enhanced efficiency
• Optimized Performance
• Support for distributed applications

The disadvantage of multicast is that it uses UDP (User Datagram Protocol) as it's transport protocol. This means that packets are only sent on "best-effort" delivery and that packets aren't sent reliably. In order to cut down on unreliable packets, the multicast applications them selves may need to provide some sort of reliability mechanisms to prevent huge data lost. This could mean more processing power needed on the hosts them selves.

Shawn Moore invites you to follow my study progress at http://shawnmoorecisco.blogspot.com/. I also invite you to download my free CCNA eBook lab book at: http://www.configurethenetwork.com.

Article Source: http://EzineArticles.com/?expert=Shawn_Moore

EIGRP Challenge Lab

I did my best to get through all of the tasks for the EIGRP Challenge Lab but I was unable to complete two tasks because I wasn't sure what they we really wanting me to do. The first was to filter a specific network from advertising out of a routers interface. The other task was to filter a network from entering a routers interface. I wasn't sure if I was just supposed summarize the network or create access-lists, route-maps, etc to deny the traffic. Besides that I managed to finish every other task successfully.

I had to change EIGRP settings such as manual summarization, change hello timers, and implement MD5 authentication which was all pretty straight forward. The weirdest task preventing EIGRP from sending multicast updates between the neighbors R1 and R2 (As shown above). I think I figured it out by entering the following command under my EIGRP AS 1

Router 1
router eigrp 1
neighbor 172.16.12.2 s0/0

Router2
router eigrp 1
neighbor 172.16.12.1 s0/0

If any one has any better suggestions on how to limit multicast addresses or if my method was completely wrong, please let me know haha!

A Few Different CCNA Lab Simulation Options

As all of us Cisco certified and future Cisco certified professionals know, the key to passing the CCNA is knowing your hands on configuration like the back of your hand. This presents a challenge to many of us who's budget is limited from buying the latest and greatest Cisco equipment that could cost anywhere from hundreds to thousands of dollars to create a decent lab!

Fortunately many simulation programs are out there to help replicate the hardware and software needed to pass the exam. Even newer to the Cisco world and in my opinion closer to the real thing is emulation software that uses the actual IOS to simulate working on a Cisco router.

Simulation programs provide a very affordable way to create labs to possibly pass the CCNA exam with the bare minimum requirements. There are many simulation programs to choose from. In particular you would want to look for something that has many different Cisco devices to play with along with being updates with the newest IOS commands.

This is something you should note because it's not uncommon for different IOS versions to use a slightly different set of commands to accomplish the same task. Before choosing a simulation program it is also valuable to note that you won't have access to every feature available with a real router and equipment so many commands will not be available to you.

There's also the option of using emulation software such as GNS3 which allows you to completely emulate a Cisco device without the actual hardware. You can also do cool things such as connect to a real Cisco device from the emulator program to help cut down on cost if you already have a few Cisco devices but not enough to create a full CCNA lab. There are a few downsides though as well. The main downside is that as of today, you aren't able to emulate Cisco Switches due to the way Cisco switch hardware works.

However emulators such as GNS3 has a simple Ethernet switch built in that you could use or you can connect your emulated network to an outside world to connect to your Cisco switches. The other downside is that you must have access to actual IOS images in order to use any of the emulator device. This can be particular hard to acquire unless you are a vendor or a CCIE with credentials to access these images from Cisco directly. There are many choices out there but always remember that nothing beats actual equipment and hardware!

Check Out My CCNA Lab Book At: http://www.configurethenetwork.com That Features Over 15 Scenario Based Real World Labs!

Article Source: http://EzineArticles.com/?expert=Shawn_Moore

EIGRP Configured on a Frame Relay Network

I spent a little time this afternoon going over the next EIGRP lab in the CCNP Lab Portfolio. I learned some useful types regarding EIGRP and how it works over Frame. For the most part you can configure EIGRP as normal but EIGRP works off of split-horizon rules. Split horizon pretty much tells a router not advertise a route out of the same interface that it learned the route from to begin with. There for in the diagram router West and East didn't know about each other due to not being able to advertise the same route back to HQ. To get past this, I had to turn of split horizon on the HQ router with the following command:

no ip split-horizon eigrp 1

Once I entered this command under the EIGRP configuration, sure enough all routes came right up!

EIGRP Configuration, Bandwidth, and Adjacencies

I was able to tackle the second lab in the BSCI Lab Portfolio and I can already say with confidence that this book will help me greatly with my studies. I learned a few things between this lab and he first lab that I wouldn't of ever known or thought about. Last week was a very simple two router lab with basic static route configuration. However I learned something that I didn't even know these Cisco routers could do, and that's programming scripts. The Lab Portfolio goes over a neat little script that allows you to test ping configurations without having to go through and ping every interface over and over on each router to verify connectivity. Check out a preview of the script I used for the first lab below, it's called TCL Script and you can access it by typing the tclsh command when you are in enabled mode:

foreach address { 10.1.1.1 10.1.2.1 10.1.3.1 10.1.4.1 10.100.12.1 10.2.1.1 10.2.2.1 10.2.3.1 10.2.4.1 10.100.12.2 } { ping $address }

It pretty much says for each IP address listed, ping it, as simple as that!


I finished my first EIGRP lab today and picked up some cool new commands such as the ping ip address repeat number of times command. Which you can ping an IP address as many times as needed, an example would be ping 10.1.1.1 repeat 1000. This tells the router to ping 10.1.1.1 1000 times, great for testing experiments with routing protocols while packets are being sent across the network!.

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Route Reflectors For BGP

BGP specifies that routes learned using Interior BGP should never be learned by other IBGP peers. Because of this rule, BGP requires that all IBGP networks to be complety fully meshed as shown in the picture above. Therefore if you had just 13 routers in your AS running IBGP, you would need 78 total connections in order for all 13 routers to connect to every other router! This causes a big problem with bandwidth due to sending redundant data across all of the routers at the same time.

To over come this, the creation of Route Reflectors (RR) were created. Route Reflectors allows an AS that's running IBGP to not have to use a complete full-mesh topology. Instead you can creat whats called clusters which can group sets of routers together. You can think of a cluster as a mini network that sits inside of your AS. But instead of a full-meshed topology, the cluster is designed in a hub and spoke fashion with one router being designated the Route Reflector (Hub) and the other routers being the spokes that connect to the RR. The Route Reflector then passes its updates to the AS, other clusters, or even other AS's depending on the configuration. This saves on the number of BGP TCP sessions that must be maintained and and also reduces the BGP routing traffic!

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BGP Communities

If we used just prefix-lists and distribute lists to filter BGP updates it would be a very manual intensive job due to the size of most BGP networks and the fact that you would have to configure each router one at a time! Today I learned that you can group routers running BGP into groups that can share the same filtering information. Therefore you would only need to configure one of the routers in the group for all of the other routers to know what updates should be filtered and what shouldn't.

"BGP communities function allows routers to tag routes with an indicator (the community) and allows other routers to make decisions (filter) based on that tag. BGP communities are used for destinations (routes) that share some common properties and that, therefore, share common policies; routers, therefore, act on the community, rather than on individual routes. Communities are not restricted to one network or autonomous system, and they have no physical boundaries."

the community attribute is considered an optional transitive attribute. If a router receives an update with community attribute information but doesn't use that attribute, it will ignore it but pass it along to other BGP neighbor peers. The community attribute consists of 32-bits, 16 for the Autonomous System number (AS) and the other 16 identifies the community number.

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Creating Prefix-Lists for BGP Routing 2

I spent this early afternoon finishing up the BSCI BGP Appendix section on prefix-lists for BGP, I mainly created a lab that specifies that that the network 172.30.0.0 /24 in the AS 65500 only shows as the supernet 172.0.0.0/8 in the AS 65000 BGP table as shown above. Tomorrow I will learn a little bit about BGP communities and go over what I've learned!

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Creating Prefix-Lists for BGP Routing

I spent a good bit of my morning learning and configuring BGP prefix-lists which I will wrap up tomorrow most likely. Prefix-lists provide greater flexibility over access-lists due to the fact you're allowed more granular control of where you want input your statements inside the prefix list. This differs from the standard access-list where one no command on the ACL requires you to recreate the access-list completely! I'm still not entierly sure how prefix-lists differ from ip access-list commands which allows you to enter sequence number states like prefix-lists. I do know that you can control exactly how you want a neighbor BGP autonomous sysstem (AS) to know about external routes by using the le and ge commands.

The le and ge values are used in a prefix-list statement to create a range of the prefix length to be matched more specifically compared to the network/length commands used in the prefix-list statements. Prefix lists do provide the advantage of being less performance intensive due to not requiring the amount of route lookup processing sometimes required by large access-list tables.

As you can see in the above lab I worked earlier, the prefix list tells AS_65000 to only let AS_65002 know about the 172.16.0.0 /16 external network instead of the more specific 172.16.10.0 /24 and 172.16.11.0 /24 routes.

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BGP Summary and Aggregated Routes

I spent this morning briefly covering how to summarize routes in BGP using CIDR Aggregated Routes. BGP specifically uses the Atomic Aggregate attribute which is considered one of the well-known discretionary attributes. BGP also uses the optional transitive attribute called an Aggregator which specifies the BGP ID and the AS that performed the aggregation in BGP updates. If you aren't careful when planning which routes to summarize your AS could easily claim routes that it really doesn't own which could upset other AS's in the BGP system! AS's doesn't really use aggregation as much as they could because some are multihomed to many ISP's and would rather make sure that all of the routes that own are being advertised without being summarized into one route.

Policy Based Routing 2

This morning I created another PBR lab that I was able to wrap my head around a lot easier than yesterday. As you see in the above image, there are 3 routers in which specific LAN traffic from Router C should be routed out of Router A's Serial 0/0/1 interface. It was good to get some more hands on with route-maps the past few days. I'm going to work some more labs throughout the day most likely on BGP. My lab guide book should be here in another weeks so you should be seeing a ton of new labs from me here shortly!

Policy-Based Routing

Now that I finished the main book for BSCI, I'm now reviewing everything I learned and will spend most of my time creating labs and touching up the details. But before I do to much, Cisco was kind enough to include 5 extra Appendix PDF files to learn about some technology in even more detail. This is mainly appendixes on how to manipulate packets and even more BGP no surprise! I hear that in order to fully be perpared for the BSCI you have to dig even deeper than what the Self Study Guide book provides. This includes everything from reading white papers, CBT's, and creating labs for pretty much ANYTHING related to the exam.

Today I learned a little bit about Policy Based Routing (PBR) which is basically route-maps on steroids. Similar to how there are access-lists and then extended access-lists (access-list on steroids), PBR allows you to maniplulate routes in a more granular manner. Tomorrow I'll be finishing this appendix up and moving to the last few that are left.

Don't forget to download my FREE CCNA Lab book for the ICND1 course at www.configurethenetwork.com while it's still available. The full version of the lab book is FINISHED and ready to sell, I'm just working on some things on the back end. The full lab contains 17 scenario based CCNA labs that will test your theory on every topic included in the CCNA

IPv6 End of Chapter Configuration

Well I Finally Finally Finally made it through the entire CCNP Self Study Guide book. I polished off the rest of the book by finishing the end of chapter lab for IPv6. I managed to get through most of the tasks successfully but I'm still having troubles setting up IPv6 tunnels and I'm not sure why. Even after mirroring the configuration settings exactly, I've been unable to bring the tunnels up. Hopefully I can figure out what was missing by doing a little research aka Google. The next step for me will be going through the exam-guide and lab guide, I'm hoping to get through these two books in about two months so I can sit the test in April!

IPv6 OSPF Configuration

Today I configured a simple OSPF network using Ipv6 as my routed protocol. When using IPv6 to create an OSPF network, there are many differences and also similarities with IPv4. The main difference is obviously you're using the IPv6 format instead of the traditional 32 bit addressing scheme. Another difference involves having to manually create a 32 bit Router ID, this was optional in IPv4 but it is required for IPv6. One other thing I noticed is that you can implement OSPF on specific interfaces (links) rather than for specific subnets. Tomorrow I will be finishing up the last of the IPv6 theory which talks about transitioning from IPv4 to IPv6. Only a few more pages and I'll actually be completly finished with the self study guide! After I finish this book, the next step for me will be going through the lab and exam books to tidy up on everything l learned and prepare to take the BSCI test in the next coming months.

Ipv6 Anycast Addresses

I spent some time over the past few days learning more about the many types of IPv6 addresses out there. A new address type made specifically for IPv6 is called the Anycast Address. IPv6 Anycast addresses are global addresses, theses addressed can be assigned to more than one interface unlike a Ipv6 unicast address. Anycast is designed to send a packet to the nearest interface that is apart of that anycast group.

The sender creates an anycast packet and fowards the packet to the anycast address as the destination address which goes to the nearest router. The nearest router or interface is found by using the metric of a routing protocol. However in a LAN setting the nearest interface is found depending on the order the neighbors were learned. The anycast packet in a LAN setting forwards the packet to the neighbor it learned about first. Anycast was first proposed in 1993 but even to this data there isn't much usage as of yet. There are actually only a few anycast addresses currently assigned!

The source sending the anycast path can use the address to control the paths that traffic flows. For example, when a customer has multiple connections to multiple IP's using BGP. The customer can create a different anycast address for each ISP, and then configure the same anycast address on the closest router to that specific ISP. Therefore the routers along the source's path to the ISP can determine the shortest route based on the IPv6 anycast address. Which then forwards the packet based on the routers closest anycast address link. Another example would be on a LAN link. All the routers on the same LAN can have the same IPv6 address so that distant devices only need to identify the anycast address.

IPv6 Unicast Addressing

The IPv6 global aggregatable unicast address, also known as the IPv6 global unicast address, is the equivalent of the IPv4 global unicast address. A global unicast address is an IPv6 address from the global unicast prefix. These global unicast addresses are designed in a way so that their prefixes can be reduced making for more efficient routing due to a decreased routing table size. Global unicast addresses used on links are aggregated upward through organizations and eventually to the ISP's. This also allows for more efficient and scalable routing within the Internet, an improved bandwidth and functionality for user traffic.

A global unicast address typically consists of a 48-bit global routing prefix, a 16-bit subnet ID, and a 64-bit interface ID that's usually in the EUI-64 bit format.The subnet field is similar to the IPv4 subnets, organizations can use the subnet ID to create their own local addressing hierarchy. This field allows an organization to use up to 65,536 individual subnets!

The current global unicast address assignment by the Internet Assigned Numbers Authority (IANA) uses the range of address that start with the binary value 001 (2000::/3). This is one-eighth of the total IPv6 address space and is the largest block of assigned addresses. The IANA then allocates the 2001::/16 prefixes to the registries.

IPv6 Link-Local addressing have a scope limited to the local link and are dynamically created on all IPv6 interfaces by using the specific link-local prefix FE80::/10 and a 64-bit interface identifier. Link-local addresses are used for automatic address configuration, neighbor discovery, router discovery, and by different routing protocols.

IPv6 Theory

I started the last chapter of the CCNP Study Guide book today which is about implementing IPv6 (IP Version 6).IPv6 is a technology developed to overcome the limitations of the current standard, IP Version 4 (IPv4). The major shortcoming of IPv4 is its limited amount of address space. With the amount of IP enabled devices growing at a steady rate, many regions throughout the world are seeing a need for more IP addresses. In the United States, the Department of Defense (DoD) is a primary driver for the adoption of IPv6 and has set a date of 2008 for all systems with the US government to be set to this standard.

IPv6 allows for better scalability with networks and supplies what seems like a limitless amount of IP addresses to use. IPv6 provides the following enhancements:

• Larger address space - IPv6 address are 128 bits which is 4 times larger than IPv6's size of 32 bits. IPv4 had approximately 4,200,000,000 possible address while IPv6 has 3.4 x 10(38) possible addresses. The number is so big that it is alot simpler to see it in arithmetic form!
• Simplified header - IPv6 has a simpler header compared to IPv4 which allows for fast processing. IPv6 is designed in a way that check-sums aren't needed to be computed at every node unlike IPv4.
• Support for mobility and security - Mobility and security help ensure compliance with mobile IP and IP security (IPsec) standards. IPv6 provides a standard that allows IP addresses to move across areas without breaking the established connection. IPsec is also enabled by default for all IPv6 devices. IPv4 doesn't provide either mobility or IPsec security options by default.

IPv6 has three main types of addresses that are similar and different from IPv4:

• Unicast - Similar to an IPv4 unicast address, an IPv6 unicast address is for a single interface. Like IPv4, a subnet prefix is associated with each address. The two different types of unicast addresses are global aggregatable and link-local
• Anycast - Is a new address type that is assigned to a set of interfaces on different devices using IPv6. A packet that is sent to an anycast address goes to the closest interface identified by thr anycast address. Therefore all nodes using the same anycast addess should provide the same type of service.
• Multicast - An IPv6 multicast address identifies a set of interfaces on different devices. A packet sent to a multicast address is delivered to all the interfaces that is apart of that multicast group similar to IPv4.

IPv6 doesn't have broadcast address like IPv4 does. Broadcasts are replaced by multicasts and anycasts. Multicast enables efficient network operation by using a number of specific multicast groups to send requests to a limited number of computers on a network. Multicast groups prevent most of the problems that happens with broadcast storms on IPv4.

IP Multicast Configuration and Verification

I finished up the rest of chapter 9 on Multicast by learning a little mor PIM theory along with simple configuration of multicast. When configuring PIM-DM (Dense Mode), it initially floods unicast traffic being sent by the source throughout the entire network. As each router receives multicast traffic via its RPF interface (the interface in the direction of the source), it forwards the multicast traffic to all of its PIM-DM neighbors.

PIM-DM prune messages are sent to stop unwanted traffic. Prune messages are sent on a RPF interface when the router has no downstream receivers for multicast traffic for that source. Prune messages are sent to non-RPF interfaces to shut off the flow of multicast traffic because it is arriving via an interface that is not the shortest path to the source.

PIM-SM (Sparse Mode) uses shared distribution trees with RP's (Rendezvous Points) but may uses source distribution trees as well. PIM-SM is based on a pull model so that traffic is forwarded only to those parts of the network that need it. PIM-SM uses an RP to coordinate forwarding of multicast traffic from a source to the receivers. PIM-SM is appropriate for wide-scale deployment for both densely and sparsly populated groups in the enterprise network. It is preferred over PIM-DM for all production networks regardless of size and membership density.

There are many optimizations and enhancements to PIM, including the following:

• Bidirectional PIM mode, which is designed for many-to-many applications (that is, many host all multicasting to each other)

• Source Specific Multicast (SSM), which is a variant of PIM-SM that builds only source specific shortest path trees and does not need an active RP for source-specific groups (in the address range 232.0.0.0/8)
  

Multicast IGMP and PIM

I learned a little more about IGMP and PIM this morning. Hosts use IGMP (Internet Group Management Protocol) to register with the router to join or leave specific multicast groups. The router is then aware that it needs to forward the data stream destined to a specific multicast group to the registered hosts. There are currently three versions of IGMP, versions 1, 2, and 3.

• IGMPv1 - periodically sends membership queries (60-120 sec) to the all-hosts multicast address 224.0.0.1. IGMPv4 doesn't have a mechanism defined for hosts to leave the multicast group. There for IGMP routers learn that a group is no longer available when it times out from not receiving any queries from that particular group.

• IGMPv2 - has group-specific queries that allows a router to query membership only in a single group instead for all groups. Instead of waiting for a timeout from a particular group, the last hosts that are apart of a multicast group sends the router a specific message that it's leaving said group.

• IGMPv3 - is still being designed and proposed. Version 3 adds the ability to filter multicasts based on multicast source so that hosts can indicate that they want to recieve traffic only from particular sources within a multicast group.

In order for Layer 2 devices to recognize multicast packets it uses either CGMP (Cisco Group Management Protocol) or IGMP Snooping. As you might have guessed, CGMP is a Cisco proprietary protocol designed for Cisco switches specifically. It allows you to maunally configure specific switch ports for multicast traffic but this feature isn't scable because of that reason. IGMP Snooping allows a switch to eavesdrop on IGMP messages sent between routers and hosts, and updates its MAC address table accordingly.

PIM (Protocol Independent Multicast) is used by routers that are forwarding multicast packets. PIM uses the normal IP routing table in its multicast calculations. PIM uses what's called distribution trees to forward multicast packets. There's two types of trees

• Source Tree - A source tree is created for each source sending to each multicast group. The source tree has its root at the source and has branches through the network to the receivers.
• Shared Tree - Is a single tree that is shared between all sources for each multicast group. The shared tree has a single common root, called a rendezvous point (RP). Sources initially send their multicast packets to the RP, which in turn forwards data through a shared tree to the members of the group.

PIM uses two modes that determines the type of distribution tree to use including one hybrid mode:

• PIM Sparse Mode (PIM-SM) - Sparse mode uses a "pull" model to send multicast traffic. it usres a shared tree and therefore requires an RP to be defined.
  
• PIM Dense Mode (PIM-DM) - Dense mode uses a "push" model that floods multicast traffic to the entire network. Dense mode uses source trees.
  
• PIN Sparse Dense Mode - uses both Sparse and Dense modes throughout its network
  

Multicast Overview

I'm nearing the end of my CCNP Study Guide Book, with only this chapter on multicasting and the last chapter on IPv6 to go. Multicasting enables data to be sent over networks to a group of destinations in the most efficient way. The data is sent from the source as one stream; this single data stream travels through the network. Other network devices only replicate the data through the network if they have other members on their interfaces that are apart of this destination group.

Multicast groups are identified by Class D IP addresses, which are in the range from 224.0.0.0 to 239.255.255.255. Muticast uses the Internet Group Management Protocol (IGMP) and Cisco Group Management Protocol (CGMP) for determining which network devices require the multicast data stream. Protocol Independent Multicast (PIM) is used for determining the best way to route multicast traffic.

There are many differences between Multicast and Unicast packets. Unicast duplicates a packet for each reciever that it needs to send the data too (one copy for each reciver). Multicast sends one packet stream as mentioned previously, downstream routers replicate the packets only on links where receiving hosts exist. Multicast provides the following advantages over unicast:

• Enhanced efficiency
• Optimized Performance
• Support for distributed applications

The disadvantage of multicast is that it uses UDP (User Datagram Protocol) as it's transport protocol. This means that packets are only sent on "best-effort" delivery and that packets aren't sent reliably. In order to cut down on unreliable packets, the multicast applications them selves may need to provide some sort of reliability mechanisms to prevent huge data lost. This could mean more processing power needed on the hosts them selves.

Configure the Network Full CCNA Lab Preview

Hey all, I just wanted to give you a quick snippet of one of the labs that will be available when you purchase the full version of the Configure the Network Lab book. View the picture above for a peek at what Task 8 will have you configuring for your CCNA exam!

Don't forget to download the free CCNA ICND1 Lab book at www.configurethenetwork.com

End of Chapter BGP Labs

The end of chapter 8 consists of 3 BGP labs to test your knowledge of the material you've learned so far. I went through 2 labs today and will complete the last one tomorrow along with the end of chapter questions. The nice thing about setting up and configuring the network examples in the book is that by time you get to the end of chapter labs you will know how to configure everything with ease. I noted today than I configured a total of 75 network labs so far during my BSCI studies the last few months! I'm sure that I'm going to easily pass 100 labs by time I take the exam for the first time, I just want to be as prepped as possible going in.

BGP MED Configuration

When using BGP, sometimes the Autonomous System (AS) wants to influence another AS's routing decision on how incoming packets are routed to its AS. Multiexit-discriminator (MED) is used to configure this setting for BGP peers. Unfortunately MED is one of the last considered processes in the BGP routing process. That means that if local preference is used in the BGP process it can not knowingly override any MED settings you are sending to that remote AS.

Route maps can be used with MED to better load balance settings, using the command default-metric under the BGP configuration will set MED settings. However if two BGP peers in the same AS have different MED values, the lower cost will always be preferred. While the other peer will receive little to almost no routing traffic besides BGP updates. What would be better is creating a route map that specifies which networks should have lower metrics on each BGP peer as shown in the example above.

Multiple AS BGP Lab

I spent this evening creating one of the bigger labs I usually do. My task was to setup a BGP network with 5 AS's in which every AS should be able to reach other loop-free (requirement of BGP anyways). I was also supposed to make Router C choose Router A to send its packets destined for AS 65004. Well I was able to get the BGP network up without to many hitches which is a long way than just a week or two ago. I however could not get my route-map statement for Router A to set the local preference to AS 65004 higher than Router B to work. I'm not sure why but as i finish up this chapter i will review why this command didn't take. I think it might have been the way I applied it to the BGP router configuration (had the route-map set to in instead of out). All in all I would say it was a pretty good success setting up a lab of this size without having to really reference the book for command guidance.

Configure the Network Free Lab Book

Hey everyone, check out www.configurethenetwork.com to download your free ICND 1 lab book today!

BGP Peer Groups

I spent the better part of my morning learning how to configure BGP Peer Groups. Peer Groups provide a way to save router processing time by not having to send an individual update for each IBGP neighbor. If your Autonomous System has a rather large amount of routers (neighbors) running BGP, the processing time each router would have to run could be pretty intensive. Remember that when running IBGP within a transitive AS, all neighbors should be fully-meshed with one another due to the way BGP sends updates (unicast). I was also introduced to distribution lists and how they could be used to tune BGP updates. In the lab I created I used a distribution list to permit internal IP networks from being addressed outside the AS to other AS's.

As you see in the Router A BGP example, the commands to create a peer-group, distribution list, and creating updates for specific networks can be quite extensive compared to other routing protocols.

BGP Neighbor Configuration

After reviewing my CCNP study guide book this morning I finally ran into the material that would of helped me out tremendously yesterday. Sometimes I get a head of my self when studying because I will lab or study topics which hasn't been presented to me yet. This can be good or bad depending on how you look at the situation. What I came to find out when configuring BGP is that there's a huge difference between IGP and BGP network commands. When using the IGP network commands you are determining which interfaces should be apart of the IGP routing process. When using BGP network commands, you are determining which routes in the IP Routing Table should be apart of the BGP routing process. It's also important to note that the network you are referencing in the IP Routing Table will have to exactly match in your BGP network command.

For example if you have the route 192.168.1.0 /30 in your IP routing but type the following BGP network command:

network 192.168.1.0
or
network 192.168.1.0 mask 255.255.255.0

This will not work you will have to type the following:

network 192.168.1.0 mask 255.255.255.252

In order for BGP to include this route in the routing process.

Configure the Network Free Lab Book

To all of those who haven't signed up to the mailing list, I wanted to let you all know that the free lab eBook should be complete within the next two weeks! The people who are signed up to the mailing list will be the first to gain access to the download once it's complete. You can sign up on the right side of this blog, I try to send out a news letter weekly.


There will be two versions of the CtN Lab book. The free version will be based off of mostly ICND1 material. The full version will contain the following:

-Working Solutions for all labs

-More than twice the amount of labs offered in the free lab book

-Both ICND1 and ICND2 material (Entire CCNA Exam Blueprint)

And many more features to come! Pricing has not yet been determined for the full lab but I want to make sure that's it's more than affordable to everyone. If you have any questions please feel free to email me at: configthenet@hotmail.com

Configuring BGP

I spent most of my early afternoon configuring BGP for the first time. I was honestly a little nervous about if I was going to get this protocol up and running because I hear so many stories about how in-depth this particular protocol was. It actually took me a little while to get my lab up and working with this protocol because I wasn't sure if i needed to synchronize my BGP routes with my IGP (EIGRP) or not. I ended up using loopback interfaces as my update sources and configured my AS 65101 as a full-mesh BGP even though I' sure I didn't need to in retrospect since the AS wasn't a transitive AS.

Transitive AS's pass on BGP routes from one AS to another AS, in other words it's like a middle-man in the BGP routing process. I also had problems with my network statements, at first I didn't realize you even needed to use network statements since you were using the neighbor commands. Even after using network commands my BGP routes still wouldn't propagate to each other. After a little research i decided to define the specific subnets that I wanted to be used for routing updates. As soon as I did that all the routes came right up!

BGP Attributes

Today I studied the different BGP Attributes that are used to determine routes. There are Well-Known Attributes and then there are Optional Attributes. Well-Known attributes must be recognized and propagated to BGP neighbors. Optional Attributes may be propagated to neighbors depending on the attributes meaning. Within these two types of attributes, there are sub attributes.

Well-Known Mandatory Attributes (Must be included in BGP Updates):
- AS-path
- Next hop
- Origin

Well-Known Discretionary Attributes (Not mandatory to be included in BGP Updates):
- Local preference
- Atomic aggregate

Optional Transitive Attributes (Must be passed to other AS's even if attribute isn't used):
- Aggregator
- Community

Optional Nontransitive Attibutes: (Doesn't have to be passed to other AS's):
- Multiexit-discriminator (MED)

I've also reviewed how BGP Synchronization works along with the many BGP message types. Synchronization tells BGP to wait until all routers have the same IGP information before updating other AS's with the info when using redistribution of BGP into IGP. From what I've been reading synchronization is outdated as most BGP updates are to large to be redistributed into IGP's anyways (scalability). BGP message types are used for establishing BGP neighbors along with providing keep-alives and BGP router updates

BGP Path Vector Characteristics

I spent my morning learning about BGP and its path vector technology. Path Vector is like an updated scalable version of distance-vector routing. However it has one main difference than any other distance-vector or IGP. BGP doesn't use broadcasts or multicasting since it uses TCP as it's transport protocol. TCP is used because it's able to send a large amount of data reliably, the BGP table has over 190,000 entries in the full routing table currently! This size would actually be in the millions but thanks to technologies such as CIDR, the table size has been reduced considerably. Since BGP doesn't use any type of broadcasting mechanism, an AS being use to transit BGP routes between other AS's must be fully meshed within the transit AS. In other words every router running BGP in a transit AS must be seen by every other BGP router in that AS. this is becuase the BGP updates are sent as unicast messages which aren't forwarded in a multicast manner i.e. one-to-one mesages.

CCNA Configure the Network free lab book is on the way soon! I should be completed with all of the labs for this eBook by sometime next week. I will also need my work to be edited for the final version as well. If you haven't already please subscribe to the mailing list on the right to be the first to receive updates and a link to download the free CtN CCNA lab book!

CCNP BGP Overview

Well today I finally started the chapter for BGP, I've been waiting to get to this one for a while. I went over the first section of this chapter which gave me a brief overview of what BGP is. I can already tell that there is a lot to this protocol looking at the number of RFC's alone! The fact that this is the biggest chapter in the book (over 100 pages) is another reason. I ended my study session by viewing a few multihoming options an AS has when receiving EBGP updates from multiple ISP connections.

Don't forget to sign up on my mailing list to the right to be the first to receive my free CCNA lab book! The book is only a few weeks away to being completed!

Chapter 7 BSCI Configuration Labs

Today I finished up the end of chapter configuration labs which helped me wrap my head around all of the topics presented. Everything went fairly smooth but I will need to review the commands and variables for distribute lists, route-maps, and dhcp settings. These 3 commands gives the engineer a ton of flexibility in tuning routes for a network.

In other news, I am a little more than half way finished with the free lab book I'm creating and I plan to be finished in about 2 weeks. If any one is interested on being notified when the final product is finished, please subscribe to my mailing list on the right!

Progress on the first "Configure the Network" eBook

Thanks to all the people who replied and all of the positive responses so far for the CCNA Lab book. If you're interested in receiving a copy please sign up on the right with the mailing list I just created! I'm using this as a way to keep things organized as a ton of emails have flooded in and i don't want to mistakenly leave any one left out. as mentioned I am breaking this CCNA lab book into two parts for the ICND1 and ICND2 respectively. Below you'll see the rough draft of the outline I have created for the ICND1 labs. I'll also keep you updated via the mailing list so stay tuned!


I. Introduction

1. Configure the Network

2. Contoso Technologies

II. Contoso Task 1

1. Configure Client’s Cisco Switch

III. Contoso Task 2

1. Design and Configure Client’s SOHO Switch Network

2. Implement and Verify Switch Security Measures

IV. Contoso Task 3

1. Configure Client’s Cisco Router

V. Contoso Task 4

1. Configure Small Business Client’s LAN Network

2. Create DHCP Solution for LAN Network

3. Implement Solution to Access Remote Building’s Network

VI. Contoso Task 5

1. Develop LAN Network for College Campus Buildings

2. Provide Access to other Campus Buildings Using RIP

VII. Contoso Task 6

1. Configure Client’s T1 WAN Link

2. Change WAN Link for Multi-Vendor Use

3. Install Multi-Point Connection for Redundancy

VIII. Contoso Task 7

1. Build Cisco Inter-Network for Medium Business Client

Feel free to leave comments on what you would like to see on this lab!

Tuning Route Redistribution using AD

Today I went through a quick study session and lab that shows how administrative distance can cause suboptimal routing when using route redistribution. I tested this with a lab that was redistributing RIP and OSPF both ways. Since OSPF has the default AD of 110 and RIP has an AD of 120, the ASBR routers redistributing chose the OSPF routes even when the RIP routes were closer. To modify this I had to create an access-list with all the possible RIP routes and assign it the AD of 125 on the two ASBR routers and inject the access-list into the OSPF routes. Now when the ASBR's received a RIP route from OSPF (due to redistribution) it automatically had an AD value of 125 which was larger than the default RIP AD 120. The RIP routes were installed into the ASBR's routing table due to having a lower AD value of 120!

Route Maps and Distribution Lists

I spent most of my afternoon covering the topics for Route Maps and Distribution Lists. I've actually been waiting to get to this topic for quite awhile because I see these commands in my work environment all the time. Both of these tools are similar to access-lists but their purpose is to tune or route specific IP packets. Distribution lists filter routing updates which is something you can't do with a regular access-list. Route maps gives the engineer a lot of flexibility on what specific ip packets should be tuned and what should be tuned such as the router metric. Tomorrow I will learn more about tuning administrative distance (AD) to control the flow of routing packets.

Controlling Routing Updates

This morning I spent most of my time learning about passive-interfaces and the many ways we can control and tune routing updates. This chapter actually puts together a lot of pieces to the puzzle because it explains how routing protocols work together and how you can limit what each protocol knows about the other specifically. I also learned a little bit about distribution lists and will be creating a few labs for this tomorrow.

In other news I'm creating a lab ebook for all of you CCNA test takers out there so be on the look out for that. I will most likely make it a series along with splitting the ebooks up into ICND1 and ICND2. I want to make sure that the series is not only helpful but also very affordable because we all know that the study material, equipment, and exam isn't cheap by any means. I'm actually looking to hand out a few beta copies of my book for free to review and provide constructive criticism. Email me at shawnmoore_1@hotmail.com if you're interested and I'll add you to my current list of reviewers, spots are already filling up so be hasty!

Redistributing between Routing protocols

Today I spent most of my time going through the various redistributing differences between routing protocols. The hardest redistributing to remember was the metric for the protocols that used distance-vector technology which is RIP, EIGRP, and IGRP. The metric for these protocols have a default value of infinity which means that any other routing protocol wouldn't be redistributed unless you defined the metric that is to be used. Also OSPF doesn't redistribute classless IP routes by default, you have to specify that subnets will be used for whatever reason. IS-IS was surprisingly the easiest but maybe that's because I just finished that chapter last week? I have a ways to go to finish this chapter won't be until sometime next week most likely. I will run through some labs in my portable command-guide the next few nights to get some more practice with the theory I've learned so far.

Chpt. 7 Redistribution Overview

Today I went over the beginning pages of Chapter 7 regarding manipulating routing updates. This chapter started off with route redistribution which I have a little experience with all ready from previous labs and on the job experience. The pages I read went to the reasons why you would want to redistribute and situations that you want to look out for when injecting different AS protocols into another AS protocols. There really wasn't much to lab but I did create a lab based on an example provided in the study-guide book. Tomorrow should be a lot of configuration using the various routing protocols that has been learned through out the book so far.

Chapter IS-IS End of Chapter Lab

Today I finished up the short Chapter 6 lab on IS-IS and actually managed to get everything up and working this time. I'm still not sure why my other IS-IS lab wouldn't inject the routes correctly as I should so I'll probably run over that labs configuration again at some point. I also ended the chapter by finishing the multiple choice questions presented. As current CCNP's and above mentioned, the questions presented in the back of the book are CCNA level type of questions which really doesn't help enforce your command of the topics given.

I'm actually only 4 chapters away before finishing the entire book so I'm making really good progress thanks to the holidays I was able to get some extra study time in at work. Once i finish the study guide and go through the portable command-guide book I'm going to purchase the exam and lab guide and double up my studies. Once that's complete I'm going to hopefully fill in any gaps by going through any labs and CBT's from Cisco.com I can get my hands on along with going through white papers and RFC's. Repetition Repetition Repetition is the key to mastering and becoming successful with anything I believe, hopefully it pays off for the exam!

IS-IS Configuration

Well i finally came across a lab for IS-IS, this is going to be a topic I'm going to have to come back and review a little harder for sure. The most confusing part about configuring IS-IS is remembering that a IS can only be in one area unlike OSPF but the interfaces on the IS can be set to send specific IIH PDU's (L1, L2, or both). There isn't an ABR like OSPF that sits in between two areas, also IS-IS doesn't use an area 0 bypassing hierarchy which allows for better scalability with IS-IS. I had some problems getting my loopback interfaces to connect via IS-IS even after redistributing my connected links into IS-IS I had problems. Tomorrow there's the end of chapter lab so hope fully i can better get my head wrapped around it! I also tested some SSH connections by setting up static host mappings using the ip host hostname ipaddress subnetmask command. I created loop back interfaces for my host ip address which as we know never shuts down compared to using a real serial or Ethernet interface. I want to start some security but I know my time will better spent focusing on the core CCNP topics. I'm going to have focus on all the topics presented thoroughly in order to pass the BSCI.