Wednesday, May 5, 2010

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 :)

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