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RE: MPLS CE-PE EIGRP routing for backdoor links posted 07/06/2007
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Yes, that's what most of the reading material says, but I started second guessing it when I tried it and it didn't work. When I redistribute my EIGRP routes into MPBGP the cost community is not created please look at the following:

PE2#show ip bgp vpnv4 vrf cus1
BGP routing table entry for 1:5:, version 9
Paths: (1 available, best #1, table cus1)
Advertised to update-groups:
Local from (
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

It should be listed under Extended communities, but it's not. Any idea why?


From: sam s <samarth_04@xxxxxxxxxxx>
To: Dave Williams <kapsi1911@xxxxxxxxxxx>
CC: <ccielab@xxxxxxxxxxxxxx>
Subject: RE: MPLS CE-PE EIGRP routing for backdoor links
Date: Fri, 6 Jul 2007 10:50:01 +0530

The eigrp costcommunity feature makes the PE router compare the eigrp routes and vpnv4 bgp routes with the metric value of eigrp and does not take into account of the AD.
The mpbgp routes carry the metric's of eigrp through extended community.


> From: kapsi1911@xxxxxxxxxxx> To: ccielab@xxxxxxxxxxxxxx> Subject: MPLS CE-PE EIGRP routing for backdoor links> Date: Fri, 6 Jul 2007 00:59:53 -0400> > 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 > when it is redistributed into BGP from EIGRP:> > router eigrp 1> auto-summary> !> address-family ipv4 vrf cus1> network> 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 remote-as 1> neighbor update-source Loopback0> no auto-summary> !> address-family vpnv4> neighbor activate> neighbor 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> BGP routing table entry for 1:5:, version 9> Paths: (1 available, best #1, table cus1)> Advertised to update-groups:> 1> Local> from (> 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> > _________________________________________________________________>> > _______________________________________________________________________> Subscription information may be found at: >

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