MPLS - VRF - BGP Question

billscott92787

Hey guys,




I figured I'd post this question here because I'm curious. I haven't been on the boards too much between work, studying, and family time here recently. In the CCIE R&S study guide they show an example of MPLS/VPN configuration, which the main peering between the ISP router and the Customer Edge, is being done by EIGRP, and then redistributing the provider routes from BGP. I read somewhere that normally the customer will pick their own IGP to peer with the ISP (such as EIGRP) and go from there. This can be done with eBGP correct? I am wondering, because when I was labbing it out, I created a VRF for an two separate customer routers, after configuring everything, BGP would sit in idle state. I know I am missing something. When I reconfigure it I'll post my config here.

billscott92787

I think the configuration end that I am missing is on the Provider router itself, when defining the VRF and everything. I assigned the VRF to the interface, reconfigured the ip address, since it removes it.

ColbyG

Post your config and some show commands. I'm not following exactly what you're doing. You have an iBGP relationship with another PE, I assume, and you're running EIGRP PE to CE, correct? Are you redisting your EIGRP routes into BGP?

Edit: Just a side note, but in the real world most SPs prefer to use BGP from PE to CE, in my experience.

rakem

billscott92787 wrote: »

I think the configuration end that I am missing is on the Provider router itself, when defining the VRF and everything. I assigned the VRF to the interface, reconfigured the ip address, since it removes it.

Yep, when you put the 'ip vrf forwarding' command under an interface it removes the IP so you need to re-enter it.

You should be able to use eBGP or iBGP from CE to PE.
On the PE you would just need to make sure you put the neighbour statements under the address-family command.

billscott92787

ColbyG wrote: »

Post your config and some show commands. I'm not following exactly what you're doing. You have an iBGP relationship with another PE, I assume, and you're running EIGRP PE to CE, correct? Are you redisting your EIGRP routes into BGP?

Edit: Just a side note, but in the real world most SPs prefer to use BGP from PE to CE, in my experience.

I'll post my configs when I get to work today. I want to use BGP between the PE and CE. But, when I try to set up BGP, the neighboring never takes place. I believe I'm missing something under the address-family. So, when I get to work, I'll post what I have here.

billscott92787

I figured it out, I was defining the neighboring statements under the address-family vpnv4 instead of ipv4 on my router. After configuring:


address-family ipv4 vrf Cust1
neighbor 10.1.1.2 remote-as 65002
neighbor 10.1.1.2 activate

BGP peering came up. So I know where I messed up. Thanks for your help you guys. Back to the BOOKS!!!

Forsaken_GA

rakem wrote: »

You should be able to use eBGP or iBGP from CE to PE.

Just a note on this, and someone please correct me if I'm wrong, but I believe only eBGP is available as the CE-PE routing protocol, and that you can't use iBGP. At least, not in IOS

rakem

Forsaken_GA wrote: »

Just a note on this, and someone please correct me if I'm wrong, but I believe only eBGP is available as the CE-PE routing protocol, and that you can't use iBGP. At least, not in IOS

The CCIE cert guide on page 855 just says 'Any IGP, or even BGP can be used as the routing protocol' (between PE and CE)

Might try and lab it up later using both iBGP and eBGP

Forsaken_GA

rakem wrote: »

The CCIE cert guide on page 855 just says 'Any IGP, or even BGP can be used as the routing protocol' (between PE and CE)

Might try and lab it up later using both iBGP and eBGP

Yeah, I think that's Odom making a bad assumption. page 233 of MPLS Fundamentals has a note that says

"Current Cisco IOS does not support internal BGP as the PE-CE routing protocol. It supports only external BGP"

Of course, without either side naming IOS versions at time of writing, yeah, labbing it up is about the only way to tell.

I can't think of a reason why it'd be a good idea to run iBGP as a PE-CE protocol even if it is possible.

ColbyG

Check this out:

draft-ietf-l3vpn-ibgp-01 - Internal BGP as PE-CE protocol

Forsaken_GA

Well, I guess that answers that, the draft is about 45 days old, so I doubt it's contained in current code.

Sepiraph

Forsaken_GA wrote: »

Well, I guess that answers that, the draft is about 45 days old, so I doubt it's contained in current code.

Actually that is version 2, version 1 came out back in May. But it is still quite new.

rakem

I labbed it up with eBGP over the weekend and it worked well.
That RFC for iBGP is an interesting read!

Forsaken_GA

rakem wrote: »

I labbed it up with eBGP over the weekend and it worked well.
That RFC for iBGP is an interesting read!

Oh, yeah. eBGP is stupid simple. Our provider gave us a choice of either bgp or static for our 4 mpls circuits.

and yeah, the RFC makes some points I hadn't considered, but I'm still not sure I'd be real big on iBGP for a CE-PE routing protocol.