BGP to BGP Redistribution

[hardik17187shah]

Hi everyone,

router bgp 5

neighbor 1.1.1.1 remote-as 50

neighbor 1.1.1.1 default-originate

neighbor 2.2.2.2 remote-as 500

neighbor 2.2.2.2 local-as 65011

neighbor 2.2.2.2 default-originate

neighbor 2.2.2.2 allowas-in 2

neighbor 2.2.2.2 soft-reconfiguration inbound

neighbor 2.2.2.2 route-map SET_WEIGHT in

no auto-summary

In above configuration, router is doing bgp neighboeship with 1.1.1.1 which is ISP-1.  neighbor 2.2.2.2 is not configured yet. I have just these commands created in notepad. My company they want to bring ISP-2 up which is 2.2.2.2 and after few months they are planning to remove ISP-1. So my question is when router will have both BGP neighbor, will routes are forwarded from one neighbor to another? also is it possible to redistribute routes ?  Both ISPs are running MPLS for our PIP.

Thanks

[smehrnia]

Hi,

Yes, if you peer with two ISP (ASes), normally you would become a Transit AS and re-advertise routes from one ISP into another. although you can eliminate this by using route-maps.

i didnt get what you mean by redistribute routes? could u elaborate?

HTH

plz Rate if it helped,

Soroush.

[hardik17187shah]

Hi soroushm,

Thanks for reply. Here both neighborship is from the same router. So if I dont add routes from one ISP into IGP, how another BGP neighbor will learn them without network command or redistribution ?  So what I understand is if I dont redistribute BGP routes into IGP than my AS will not become transit AS.

Thanks

[smehrnia · Accepted solution]

it doesnt matter how many routers u have involved in your bgp process, as far as you are running a bgp (AS), if the isp doesnt filter routes for/to ur side, the updates that you receive through bgp from ur eBGP peers will be advertised to the other BGP peers.

what you are saying regarding to BGP and IGP n redistribution is wrong, that is when you want to get a Local or Static route to be advertised into BGP, not the already BGP prefixes that came in from the other ISP.

in order to avoid the risk of being a transit AS and to advertise your Local routes to ur eBGP peers, do this:

ip as-path access list 20 permit ^$

route-map LOCAL permit 10

  match as-path 20

router bgp 5

neighbor 1.1.1.1 route-map LOCAL out

neighbor 2.2.2.2 route-map LOCAL out

plz Rate if it helped,

Soroush.