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Same hop IP address in two separate hop

olly ahmed
Level 1
Level 1

Hi All,

Can anyone help me to understand the issue what is happening here for below traceroute issue ? I am getting same hop IP address in hop 2 and 4. As from the trace report it seems 2 routers are showing each other as next hop for same destination but if it happened then a routing loop would occur but no routing loops there. Would be obliged if anyone can clarify the issue here and if possible share a sample topology with configuration / lab.

Test-RT#traceroute 10.8.4.15
Type escape sequence to abort.
Tracing the route to 10.8.4.15
VRF info: (vrf in name/id, vrf out name/id)
1 172.3.1.17 0 msec 0 msec 0 msec
2 172.18.17.15 12 msec 12 msec 8 msec
3 172.18.17.16 16 msec 8 msec 12 msec
4 172.18.17.15 12 msec 12 msec 8 msec
5 172.18.8.9 16 msec 8 msec 16 msec
6 10.87.25.78 8 msec 12 msec 12 msec

[**] 172.18.17.15172.18.17.16 are point-to-point link between two routers. where 172.18.17.16 is under my administration but 172.18.17.15 is not under my administration. So if you ask for configuration of 172.18.17.15 then I could not provide you.

BR//

Olly

7 Replies 7

It could be a loop or misconfiguration on the other end. 

Is this router Test-RT under your management? This router 172.18.17.16 is sending back the packet, do you have any default route on this router, you could verify it through:

show ip cef

show ip cef exact-route <source> <destination>




>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

Hi Moisa,

Thanks for your reply. Your required information is given below inline.

Is this router Test-RT under your management?

  • Yes

do you have any default route on this router, you could verify it through:

  • MP_FW#show ip cef vrf V90 10.8.4.15
    10.8.4.0/27
    nexthop 172.18.17.15 Vlan90

    MP_FW#show ip cef vrf V90 exact-route 172.3.1.158 10.8.4.
    172.3.1.158 -> 10.8.4.15 => IP adj out of Vlan90, addr 172.18.17.15

There might be a chance that hop

3 172.18.17.16 16 msec 8 msec 12 msec

is having destination nat configured

HI ROHANTARDEKAR,

Thanks for your response.

"3 172.18.17.16 16 msec 8 msec 12 msec

is having destination nat configured"

No, NAT is not configured.

BR//

Olly

Deepak Kumar
VIP Alumni
VIP Alumni

can you share your routing configuration from all routers?

Regards,

Deepak Kumar 

Regards,
Deepak Kumar,
Don't forget to vote and accept the solution if this comment will help you!

Hi Deepak,

I just manage 172.18.17.16 device.

cofee
Level 5
Level 5

I would suggest to run traceroute from an end host and fire up wireshark for packet analysis. This could be a software error. If next hop router was configured to send the packets back to you then packet would never reach destination unless there is a redudant path, but with traceroute results that doesn't seem to be the case.

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