MPLS CE-PE EIGRP routing for backdoor links

From: Dave Williams (kapsi1911@hotmail.com)
Date: Fri Jul 06 2007 - 01:59:53 ART

Hello all,

I've been reading up on the BGP cost community for EIGRP backdoor
enviorments and I'm a bit confused. My understanding is that it's use is
suppose to (by default) make a PE router choose a PE-to-PE IBGP route over
an EIGRP internal backdoor route.

So, let's say I have a PE router that is learning the same route from
another PE (across my MPLS cloud) as well as a CE router (running EIGRP). So
even though the CE learned route is going to have a lower AD (90), my
understanding of this feature is that it allows the two routes (IBGP &
EIGRP) metrics to be compared and picked based on low metric? The IBGP route
usually prefered because the EIGRP metric does not increase over the MPLS
cloud.

Question #1 - Is my understanding of this feature correct as it pertains to
EIGRP MPLS VPN PE-CE
                    with Backdoor Links . I'm aware of the BGP cost
community, but some additions
                    seem to have been made to support EIGRP backdoor
connections without having to
                    alter the AD manually?????

Question #2 - I'm ruinning 12.2(25)S11 but my PE routers aren't creating
pre-poi community (128)
                    entries for my EIGRP redistributed routes. Needless to
say my PE router on the
                    other end doesn't recieve this community. From the
reading I've done, my PE
                    router should create this community automatically during
EIGRP-to-MPIBGP
                    redistribution.

Here is the PE router's config that IS NOT creating the cost community for
172.16.20.0/24 when it is redistributed into BGP from EIGRP:

router eigrp 1
auto-summary
!
address-family ipv4 vrf cus1
network 10.0.0.0
default-metric 64 100 255 1 1500
no auto-summary
autonomous-system 1
exit-address-family
!
router bgp 1
no synchronization
bgp log-neighbor-changes
neighbor 65.202.0.1 remote-as 1
neighbor 65.202.0.1 update-source Loopback0
no auto-summary
!
address-family vpnv4
neighbor 65.202.0.1 activate
neighbor 65.202.0.1 send-community both
exit-address-family
!
address-family ipv4 vrf cus1
redistribute eigrp 1
no auto-summary
no synchronization
exit-address-family
!

PE2#show ip bgp vpnv4 vrf cus1 172.16.20.0/24
BGP routing table entry for 1:5:172.16.20.0/24, version 9
Paths: (1 available, best #1, table cus1)
  Advertised to update-groups:
     1
  Local
    10.0.4.1 from 0.0.0.0 (65.202.0.2)
      Origin incomplete, metric 2297856, localpref 100, weight 32768, valid,
sourced, best
      Extended Community: RT:1:5 0x8800:32768:0 0x8801:1:640000
        0x8802:65281:1657856 0x8803:65281:1500,
      mpls labels in/out 18/nolabel

Anyone able to shed some light?

Thanks,
Dave

This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:40 ART