Default route propagation in BGP

Answered Question
Jul 14th, 2007
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I have 3 routers in the same BGP cloud. R1 advertises a default route in BGP to PE1, and as such PE1 has a default route in the table for the VRF in question. I can see this on PE1 if i issue sh ip route vrf <vrf>


R1 >> PE1 >> PE2


This is not true of PE2, all VRF routes are present but not the default. if i issue the command 'show ip bgp vpnv4 all'i can see the default under the VRF.


though if i issue sh ip bgp vpnv4 vrf <VRF> command i cannot see the default route?


How can i get this route to propagate to PE2? it seems it is getting to PE2, but not going into the routing table. I have no filtering enabled.


Thanks.

Correct Answer by Harold Ritter about 9 years 11 months ago

Daniel,


In this context, the FW is used as a CE device and should be running eBGP with PE1.


The FW doesn't share a common IGP with PE1 and PE2, it should therefore be in its own AS (most likely private).


Hope this helps,

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Harold Ritter Sat, 07/14/2007 - 07:19
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Daniel,


You should definitely be able to propagate the default route via VPNv4. Can you do a "show ip bgp v a 0.0.0.0" on PE1.


Regards,

dankennedy Sun, 07/15/2007 - 03:29
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PE1


sh ip bgp vpnv4 all


Route Distinguisher: 1:100 (default for vrf TEST)

*>i0.0.0.0 172.16.1.1 0 100 0 ?


sh ip route vrf TEST


B* 0.0.0.0/0 [200/0] via 172.16.1.1, 00:04:00


PE2


sh ip bgp vpnv4 all


Route Distinguisher: 1:100 (default for vrf TEST)

* i0.0.0.0 172.16.1.1 0 100 0 ?


sh ip route vrf TEST on PE2 shows that route table does not contain the default.

Harold Ritter Sun, 07/15/2007 - 05:32
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Daniel,


The route is not valid on PE2 probably because the next hop (172.16.1.1) is unreachable. A "show ip bgp v a 0.0.0.0" on PE2 should confirm this.


Is R1 used as a CE? If so, I would just like to point out that using iBGP between the PE and the CE is an unsupported configuration. eBGP is normally used between the PE and CE.


Hope this helps,

dankennedy Sun, 07/15/2007 - 07:57
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R1 is a VRF aware firewall. This is in the same AS as PE1 and PE2. I would have thought it should be in the same AS, is that incorrect?



Correct Answer
Harold Ritter Sun, 07/15/2007 - 09:53
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  • Cisco Employee,

Daniel,


In this context, the FW is used as a CE device and should be running eBGP with PE1.


The FW doesn't share a common IGP with PE1 and PE2, it should therefore be in its own AS (most likely private).


Hope this helps,

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