BGP , question

[sarahr202]

Hi everybody

This is what  I observed at work

This is my understanding

Let say R1 is receiving a prefix( via BGP) 1.0.0.0/8 from two ISP,  Isp1 and ISP2, both routes will be installed in RIB, R1 finds the the route through ISP1 as the best and installs it in routing table.

However, I am seeing a strange implementation to save memory ( i think) at my work.  Our core folks  make some kind of configurations changes which cause R1 only to have the best route in RIB even though R1 may be receiving a prefix from many sources.

Is there any command I can use to display those routes?

Thanks

[prajithtr_2 · Accepted solution]

show ip bgp <the remote routes>

Regards

Prajith

[nkarthikeyan · Accepted solution]

Hi Sara,

Can you do check with show ip route repair-path??

Regards

Karthik

[sarahr202]

Hi everybody

Thanks  all you guys who responded also who did not  :)

This is what I found.

IP core is not doing anything special.

What I observed is typical BGP behaviour

R1  is learning the prefixes from both ISP say isp1 and isp2, R1 selects the route through ISP1 as best and installs it in routing table.  R1 then advertises it its IBGP peer say R3. R1 only advertises the best route.

R3  's RIB shows one route ( as it should as R3 is not learning the same prefix only from R1)

On the contrary R1 Rib shows  two routes one via ISP1, ISP2 as it is receiving them from two sources .

Simple thing but I did not realize that.

Thanks for your help

Have a great weekend.

[paul driver]

Hello

Not sure I understand, do you mean what prefixes that are being accepted that are advertised to you from either ISP?

sh ip bgp neighour x.x.x.x  routes

res

Paul