Re: BGP Path Preference in EIGRP PE-CE protocol

Hi Malik,

Have you read Ivan's article?
http://wiki.nil.com/Multihomed_MPLS_VPN_sites_running_EIGRP

I think that this part is key for your PE routers R8 and R7.
" This behavior effectively disables BGP route selection mechanism;
EIGRP routes redistributed into MP-BGP are compared solely based on
their EIGRP composite metric as calculated at the original
EIGRP-to-MP-BGP redistribution point."

So I would suggest on R8 and R7 doing a " show ip eigrp vrf XXX
topology 9.9.3.3/32" for example and looking at the composite
metrics. You should see one for VPN4 and one for eigrp derived. The
lower metric will then tell you what the next hop will be.

This might help you answer some of your questions.

-Rich

On Sun, Feb 27, 2011 at 8:52 AM, Malik Nouman Ahmad <djmalik_at_gmail.com> wrote:
> Hi,
>
> I know that there is a long list of BGP best path selection criteria, but I
> am unable to understand why R8 is selecting R3 as the best-path out of the
> two
>
> R8#sh ip bgp vpnv4 all 9.9.1.1
> BGP routing table entry for 9:9:9.9.1.1/32, version 67
> Paths: (2 available, best #2, table ABC)
> Flag: 0x800
> Advertised to update-groups:
> 1
> Local
> 9.9.7.7 (metric 2) from 9.9.9.9 (9.9.9.9)
> Origin incomplete, metric 5, localpref 100, valid, internal
> Extended Community: SoO:78:78 RT:9:9 Cost:pre-bestpath:128:156160
> 0x8800:32768:0 0x8801:9:130560 0x8802:65281:25600 0x8803:65281:1500
> Originator: 9.9.7.7, Cluster list: 9.9.9.9
> mpls labels in/out 22/27
> Local
> 9.9.38.3 from 0.0.0.0 (9.9.8.8)
> Origin incomplete, metric 158720, localpref 100, valid, sourced, best
> Extended Community: SoO:78:78 RT:9:9 Cost:pre-bestpath:128:158720
> 0x8800:32768:0 0x8801:9:133120 0x8802:65282:25600 0x8803:65281:1500
> mpls labels in/out 22/nolabel
>
> Is it because it is locally sourcing the path while redistributing EIGRP
> into BGP under the "address-family ipv4 VRF_A"?
>
> Same is the case on R9
>
> R9#sh ip bgp vpnv4 all 9.9.1.1/32
> BGP routing table entry for 9:9:9.9.1.1/32, version 43
> Paths: (2 available, best #1, no table)
> Flag: 0x4800
> Advertised to update-groups:
> 1 2
> Local, (Received from a RR-client)
> 9.9.7.7 (metric 2) from 9.9.7.7 (9.9.7.7)
> Origin incomplete, metric 5000000, localpref 100, valid, internal,
> best
> Extended Community: SoO:78:78 RT:9:9 Cost:pre-bestpath:128:156160
> 0x8800:32768:0 0x8801:9:130560 0x8802:65281:25600 0x8803:65281:1500
> mpls labels in/out 26/27
> Local, (Received from a RR-client)
> 9.9.8.8 (metric 3) from 9.9.8.8 (9.9.8.8)
> Origin incomplete, metric 158720, localpref 100, valid, internal
> Extended Community: SoO:78:78 RT:9:9 Cost:pre-bestpath:128:158720
> 0x8800:32768:0 0x8801:9:133120 0x8802:65282:25600 0x8803:65281:1500
> mpls labels in/out 26/22
>
> I am totally lost :-(
>
> Please help as my exam is next week and I am going totally bonkers with this
>
> Thanks,
> Malik
> On Sun, Feb 27, 2011 at 5:27 PM, Malik Nouman Ahmad <djmalik_at_gmail.com>wrote:
>
>> Hi,
>>
>> I am stuck in a bit of a puzzle.
>>
>> ---R9(RR)---
>> / \
>> R8(PE) ----- R7 (PE)
>> | |
>> R3(CE) ----- R1 (CE)
>>
>> - All routers have Lo0 with format 9.9.X.X/32 where X is the router number
>> - PE-CE protocol is EIGRP under VRF A
>> - PEs and RR have MP-BGP configured and CEs have EIGRP configured between
>> them i.e. CEs have backdoor link
>>
>> R8s routing table has
>> D 9.9.3.3/32 via 9.9.38.3
>> B 9.9.17.0/24 via 9.9.7.7
>> B 9.9.1.1/24 via 9.9.7.7
>>
>> R7s routing table has
>> D 9.9.1.1/32 via 9.9.17.1
>> B 9.9.38.0/24 via 9.9.8.8
>> B 9.9.3.3/24 via 9.9.8.8
>>
>> R3's routing table has
>> D 9.9.1.1/32 via 9.9.13.1
>> D 9.9.17.0/24 via 9.9.13.1
>>
>> R1's routing table has
>> D 9.9.3.3/32 via 9.9.13.3
>> D 9.9.38.0/24 via 9.9.13.3
>>
>> My aim is that the RR reaches 9.9.1.1/32 and 9.9.17.0/24 through
>> R9->R8->R3->R1. If R8 is down, then it can go directly R9->R7->R1. R8
>> prefers BGP routes for 9.9.1.1/32 over the EIGRP routes from R3 and
>> therefore is not loading it into its BGP table
>>
>> I am unable to do it, please help me
>>
>> Thanks,
>> Malik
>
>
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Received on Sun Feb 27 2011 - 19:21:08 ART