router on a stick...

snickeredsnickered Member Posts: 25 ■□□□□□□□□□
I have R1->S1->S2->R2

The ports of the link between S1 and S2 are trunk ports on native VLAN1.
The port on S2 connected to R2 is a trunk port native VLAN1.
R2 has the IP addresses of:
fa0/0.1 - (VLAN1)
fa0/0.2 - (VLAN2)
R1 has the IP address of:
fa0/0 -

R2 cannot ping when is specified as the source IP address.

On R2 I have:
ip route

And R1 I have:
ip route

I suspect that I need to put a subinterface on R1 but I can't see why. When I ping to from I would think the packet would be able to get to R1 because the next-hop is which is connected via

I'm confused... can someone explain what I'm doing wrong?


  • luke_bibbyluke_bibby Member Posts: 162
    have u configured dot1q or isl encapsulation on the router?

    As an example on R2:
    R2(config)# int fa 0/0.1
    R2(config-subif)# encapsulation dot1q
    R2(config-subif)# ip address
    R2(config-subif)# int fa 0/0.2
    R2(config-subif)# encapsulation dot1q 2
    R2(config-subif)# ip address

    Are your trunks on the switch to the router configured to always trunk cause routers cant negotiate trunks using DTP.

    As an example on S2:
    S2(config-if)# descr Trunk to R2
    S2(config-if)# switchport mode trunk
    S2(config-if)# switchport trunk encapsulation dot1q

    S2(config-if)# switchport trunk nonegotiate
  • snickeredsnickered Member Posts: 25 ■□□□□□□□□□
    Yes, AFAIK you can't assign an IP address to a subinterface without specifying the encapsulation first so I left that out. Also, 'sh int trunk' shows that the ports are all 802.1q.
  • luke_bibbyluke_bibby Member Posts: 162
    Ya good point, sorry!
  • kryollakryolla Member Posts: 785
    can r1 ping and then ping if r1 cant reach 52.2 then debug ip packet and see whats failing. if nothing is wrong then go to r2 and debug ip pack and see if you are receiving the pings and what is causing the failure of you responding to it.
    Studying for CCIE and drinking Home Brew
  • snickeredsnickered Member Posts: 25 ■□□□□□□□□□
    Sorry guys... it ended up being an ACL that was causing the issue. Thanks for the tips though. I'll look for these things in the future.
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