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)