ibgp default route preferred over the ebgp one

[tommar]

hello, any ideas why ibgp default route is preferred over the ebgp one? AD should elect the ebgp route. 

primaryRouter#sh ip b 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 29954754
Paths: (2 available, best #1, table default, not advertised to any peer)
Not advertised to any peer
Refresh Epoch 1
Local
10.54.122.254 from 10.54.122.254 (10.252.39.210)
Origin IGP, metric 0, localpref 100, valid, internal, best
Community: no-advertise
rx pathid: 0, tx pathid: 0x0
Refresh Epoch 1
65011 910
12.14.132.97 from 12.14.132.97 (12.14.21.141)
Origin IGP, localpref 100, valid, external
Community: 65011:110
Extended Community: SoO:65011:107933 RT:65011:5690
rx pathid: 0, tx pathid: 0

[Flavio Miranda]

Hi

" Origin IGP,"  Which others protocol are you running? OSPF, EIGRP, RIP?

Can you share the command:

show run | sec router

[tommar]

hello, thanks Flavio. 

the secondary router has default static routes redistributed to the bgp that are then sent to the primary. but the origin should not matter as the AD is the first decision maker.? both routers only have bgp as a rting protocol. 

[MHM Cisco World]

 ...

[tommar]

this is what sounds best, but do we have some official document, because why would ebgp have different AD than ibgp if it was bgp that makes the decision?

[MHM Cisco World]

...

[Jon Marshall]

BGP decides which route to choose based on a number of criteria and EBGP vs IBGP is only part of that and not the most important. 

See my previous response for the document showing how BGP makes that decision. 

Jon

[tommar]

i can accept ebgp and ibgp is one process, as path is shortest and decides but why or what use is of the different AD for e and i bgp?

[Jon Marshall]

AD is really only used for choosing between routing protocols and not within the same protocol so even when BGP is making the decision between EBGP and IBGP it is not doing it based on the AD as far as I know, it is only once the BGP route is chosen that AD would come into it ie. is there a route in the IP routing from another routing protocol that has a better AD. 

As to the values no idea how they were selected for all routing protocols although the values are meant to represent the trustworthiness of the routing protocol. 

Jon

[Jon Marshall]

Shortest AS path is before EBGP vs IBGP - 

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html

Jon

[MHM Cisco World]

..

[Jon Marshall]

You could also use local preference which is the usual one to use between IBGP peers. 

Jon

[tommar · Accepted solution]

ok, the answer is here

https://community.cisco.com/t5/routing/ebgp-vs-ibgp-path-selection-vs-admin-distance/td-p/497657

thank you all

[Jon Marshall]

Which is exactly what I have been explaining to you. 

Jon

[MHM Cisco World]

Yes you right,