RE: BGP Question

Hi

It is better to create the IP AS_path access list and match the specific AS
that you want to redistibute in your IGP.

a very good example explain by Brain Dennis in INE 4.0 Video in BGP section I
just this few days Back.

Example

ip as-path access-list 10 permit _100_

and match this as-path in route-map and during redistribution use this route
map.

the below example that you mention I did the same configuration and there was
a problem.

check the INE for detail.

Br

Roy

> Date: Tue, 25 Oct 2011 02:06:14 -0400
> Subject: BGP Question
> From: krkdgls5_at_gmail.com
> To: ccielab_at_groupstudy.com
>
> I was reading the BGP Case Studies on Cisco's site at this link:
>
>
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.
shtml
>
> It states:
>
> The network command is one way to advertise your networks via BGP. Another
> way is to redistribute your IGP into BGP. Your IGP can be IGRP, Open
> Shortest Path First (OSPF) protocol, RIP, Enhanced Interior Gateway Routing
> Protocol (EIGRP), or another protocol. This redistribution can seem scary
> because now you dump all your internal routes into BGP; some of these
routes
> can have been learned via BGP and you do not need to send them out again.
> Apply careful filtering to make sure that you send to the Internet-only
> routes that you want to advertise and not to all the routes that you have.
> Here is an example:
>
> RTA announces 129.213.1.0 and RTC announces 175.220.0.0. Look at the RTC
> configuration:
>
> If you issue the network command, you have:
>
> RTC#
> router eigrp 10
> network 175.220.0.0
> redistribute bgp 200
> default-metric 1000 100 250 100 1500
>
> router bgp 200
> neighbor 1.1.1.1 remote-as 300
> network 175.220.0.0 mask 255.255.0.0
>
> !--- This limits the networks that your AS originates to 175.220.0.0.
>
> If you use redistribution instead, you have:
>
> RTC#
> router eigrp 10
> network 175.220.0.0
> redistribute bgp 200
> default-metric 1000 100 250 100 1500
>
> router bgp 200
> neighbor 1.1.1.1 remote-as 300
> redistribute eigrp 10
>
> !--- EIGRP injects 129.213.1.0 again into BGP.
>
>
> If you take a look at diagram in the link for this secition you will get a
> better understanding of my question. Read from the part where it states
"*This
> redistribution can seem scary because now you dump all your internal routes
> into BGP; some of these routes can have been learned via BGP and you do not
> need to send them out again*" after looking at the diagram. It also states
"
> *EIGRP injects 129.213.1.0 again into BGP*" at the end. This seems wrong to
> me but please let me know if I am mistaken. My question is about the
""*EIGRP
> injects 129.213.1.0 again into BGP*". If eigrp 10 is redistributing bgp
> routes to the neighbor then the neighbor wouldn't advertise those routes
> back to RTC where it is redistributing eigrp 10 into bgp 200. If so, then
> how can EIGRP inject 129.213.1.0 back into BGP?
>
>
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Received on Tue Oct 25 2011 - 11:33:57 ART