Redistributing RIPv2 into BGPv4 1

[abidg]

Hello,

I am trying to redistribute RIPv2 into BGP on the following test topology.

(200.1.1.0)Internet<----------R1-----------R2-----------R3


R1 and R2 - Running RIPv2
R2 and R3 - Running BGPv4

R2 - Redistributing RIP into BGP and vice versa.

R1 - has the Internet connected to it - hence is also propagating a default route via RIP.

Now, I have used both of the following methods in RIP:

1) network 0.0.0.0 [with a default route]
2) ip default-network [Internet] and also advertising that [network] into RIP.

Both of these methods work for distributing a default route within RIP. But, none of these methods get a default route over to R3 via BGP - unless - I issue a network 0.0.0.0 command on R2 under BGP

I have also set a default metric under BGP.

Any clues...................

 

[abidg]

I have noticed one more thing:

on R1 if i set a default route pointing out to the Internet interface, and set the network 0.0.0.0 command under RIP on R1 - this propagates a route the Internet interface [200.1.1.0] throughout RIP on both R2 and BGP on R3.

 

[abidg]

This is what I have found to be:

Internet gateway <--- R1---(RIP)---R2---(BGP)--- R3
(200.1.1.0)


1)redistribute static under RIP and a default route on R1

If network 0.0.0.0 statement given under R2: propatates a route to 200.1.1.0 and a default route as well under bgp across to R3

If not given: only propagates route to 200.1.1.0 to R3 under BGP

2) network 0.0.0.0 OR default-information originate - under rip on R1

network 0.0.0.0 command needed on R2 for a default route to be propatated to R3 through BGP.

Can anyone confirm this behaviour or correct it?

Thanks and regards,

Abid.

 

[Cluebird]

BGP won't let you redistribute the default route from the routing table into BGP. You need to use the network statement.

Check this out:

http://wiki.nil.com/BGP_default_route

HTH

 

[abidg]

Thanks Cluebird.

Just wondering why BGP does that and why isnt this fact well documented in Cisco docs - atleast I couldnt find it in quite a few Cisco press and web site resources.

There has to be a reason for this. Not that I am trying to be too nosy but just that am interested in finding out the reason this is - may be it could teach me something I dont know.

Thanks and regards.

 

[Belushi]

It is indeed well documented as well as everything else BGP related/IGP related, and all routing protocol and operation. You just aren;t looking in the right place.

For any Cisco related documentation questions, always start with what was recently referred to as the DOC-CD. Today it is referred to as the product/technology support page which can be located here:

http://www.cisco.com/cisco/web/psa/default.html?mode=prod

As for your BGP related questions, go ahead and look here:

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/12_4/irp_12_4_book.html

I think you'll find there is far more information that you ever wished to even have. It was what CCIE candidates have access to when taking their tests. Enjoy.

 

[abidg]

I meant documentation about this specific feature of redistributing default route from IGP into BGP.

Again, you could be right as I might not have been looking in the right place.

Any chance I could purchase this set of doc on DOC-CD or Product/Technology Support Page? I guess not !!

 

[Belushi]

Its free. There is no need to purchase. Did you go to the links? You may need a Cisco login but that is free too if you want just guest access.

As for this specific feature, beleive me, if you look at the documentation there is info on pretty much every feature. So much so that specifically just for BGP I guarantee you there is more than you ever imagined.

 

[abidg]

Yup I know it is free but what I was thinking that as this is the sole resource one has access to during the lab, I could get myself into the habbit of using it and getting to know it better. Anyways will do with the online one instead.

 

[abidg]

I have a customer solution requiring mutual redistribution between RIPv2 and BGP, for resilience. I have used distribute-list on both in and out directions to avoid routing loop.

R1----------RIP------------R4
| |
RIP RIP
| |
| |
R2-------------------------R3
| |
BGP BGP
| |
PE1 PE2
| |
| |
----------MPLS Cloud---------
| |
| |
\ / \ /
- -
(Routes to remote sites across MPLS cloud)
Eg. 192.168.2.0/24 and 192.168.3.0/24

Here:
CEs: R1, R2, R3, R4
PEs: PE1, PE2
R1, R2, R3, R4 - running RIPv2.
R2, PE1 - BGP neighbors
R3, PE2 - BGP neighbors
R2 and R3 - resdistributing RIP and BGP (mutual)

Routes to remote site come from PE1, to R2, and are then redistributed into RIP. They then get across to R3 via RIP. R3 is also receiving those routes from PE2 via BGP. Now, R3 is also redistributing RIP routes into BGP.

Now, what happens is that when those remote routes also get redistributed into BGP through RIP, they come up under bgp local table as local routes. This makes sense as they are being sourced locally even though they are being redistributed. EBGP having a lower AD then RIP causes a problem. Those redistributed routes get choosen by BGP as the best routes and get sent to the R3 IP routing table. Because of this R3 get routes to remote routes via R4, which on the contrary should be pointing to PE2. When I clear the ip routing table and the BGP neighbor relationship, this all corrects itself, where R3 points to PE2 for remote site routes.

You might wonder as to why I am doing mutual redistribution. I have to make sure that the interconnectivity works in case of failures of either bgp PE1/PE2 or R1/R4 or even R2/R3.

I am still working on it and have a few ideas as to how this can be sorted out. At the same time if any of you could help in understanding with regards to what is going on and what are the ways this can be corrected, that would be great. I will also try to attach a diagram of the topology.


_______________________________________
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