IBGP route chosen over EBGP

[aprasad11]

Hi Guys,

I am trying to understand why my router chooses an internal route (IBGP) over an external route (EBGP) for the same prefix.

I am also allowing my own as in through 155.1.37.7. I am trying to simulate a BGP back door link but path is already going locally.

R3#show ip bgp 1.1.1.1
BGP routing table entry for 1.1.1.1/32, version 2
Paths: (2 available, best #2, table default)
Advertised to update-groups:
3
Refresh Epoch 1
300 54
155.1.37.7 from 155.1.37.7 (7.7.7.7)
Origin IGP, localpref 100, valid, external
rx pathid: 0, tx pathid: 0
Refresh Epoch 1
Local
155.1.13.1 from 155.1.13.1 (150.1.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
rx pathid: 0, tx pathid: 0x0

[Georg Pauwen]

Hello,

does the local AS appear in the path from the eBGP neighbor ?

Best to post the full config(s)...

[paul driver · Accepted solution]

Hello
Locally injected routes ( example: via network command) will always take precedence of ebgp routes.

As for using the backdoor command - This would involve using an IGP internally between the two rtrs that are also ebgp peers.

By default the prefix advertised by the bgp would take precedence due to admin distance of 20 so this will have preference over any IGP admin distance ( ospf/eigrp/rip)

To negate that you can use the backdoor command in bgp stanza specifying the other sites prefix,  this then will change its admin distance of the prefix to a value of 200 in the bgp table so then the igp path for the same prefix will take precedence and be injected into the rib.

res
Paul