BGP Next hop issue

Hi everyone

R1 received as an ebgp update with next hop .2 .3 .4 as expected but why that`s not happened with and and

why i see 3 times ? 3 time ?same next hop
R3 is going to advertise to R1 with next hop only one time why R3 advertise it 3 times to R1 ?because i see the next hop 3 times

That looks rather buggy to me. On R1, when you issue the command, “show ip bgp” do you actually see three entries? Is there anything that makes each one different from the others?

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sir,do you think it`s a bug ?

Okay…here’s what’s going on (I’ll just explain it for the prefix but the same principle applies for and

  1. You have a BGP “network mask” statement in R2. So this means that R2 will advertise this prefix:
    —a. via eBGP directly to R1
    —b. via iBGP directly to R3
    —c. via iBGP directly to R4

  2. When R2 sends this prefix via eBGP to R1 it sets the next-hop attribute to itself (

  3. When R3 receives the iBGP update from R2, R3 then transmits this as an eBGP update to R1. Because of the “third party next-hop” rule R3 does NOT change the next-hop to itself but instead leaves the next-hop as This is because R3 knows that R1 and R2 are in the same subnet.

  4. The same thing I described above happens on R4. It receives the route via R2 as iBGP and re-transmits it to R1 as eBGP. It does not change the next-hop because of the “Third party next-hop” rule.

For more info on that rule, please see this INE Blog posting:

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