ExtremeSwitching (EXOS)

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GRE tunnel forwarding not working

  • 1.  GRE tunnel forwarding not working

    Posted 10-16-2018 15:49
    I have created a GRE tunnel between a 460g2 and another device.
    I have configured a /31 on the GRE tunnel.
    I have enabled forwarding on the GRE tunnel.

    I am only able to ping the remote side of the tunnel from the 460 itself. I can ping using its IP of the tunnel as the source, or using another (loopback) IP of the 460 as the source.

    From a 480 connected to the 460, I can ping the 460's tunnel IP, but not the remote IP. Watching the traffic counters and sniffing on the remote device shows that packets are not even entering the tunnel, so I assume the 460 is not forwarding traffic (that doesn't originate with itself).

    This seems to be the same symptoms of when a VLAN does not have IP forwarding enabled.

    create tunnel rtr-1_xxx gre destination x.x.x.51 source x.x.x.132
    configure tunnel rtr-1_xxx ipaddress x.x.x.234 255.255.255.254
    enable ipforwarding tunnel rtr-1_xxx

    from the 460 itself:

    ping x.x.x.235 from y.y.y.73
    Ping(ICMP) x.x.x.235: 4 packets, 8 data bytes, interval 1 second(s).
    16 bytes from x.x.x.235: icmp_seq=0 ttl=60 time=25 ms
    16 bytes from x.x.x.235: icmp_seq=1 ttl=60 time=20 ms

    sho tunnel "rtr-1_xxx"
    Name Type Flags
    rtr-1_xxx GRE x.x.x.132 => x.x.x.51 U
    Total tunnels: 2

    And from the 480 attached to the 460:

    ping x.x.x.235
    Ping(ICMP) x.x.x.235: 4 packets, 8 data bytes, interval 1 second(s).

    --- x.x.x.235 ping statistics ---
    4 packets transmitted, 0 packets received, 100% loss
    round-trip min/avg/max = 0/0/0 ms

    ping x.x.x.234
    Ping(ICMP) x.x.x.234: 4 packets, 8 data bytes, interval 1 second(s).
    16 bytes from x.x.x.234: icmp_seq=0 ttl=64 time=1.053 ms
    16 bytes from x.x.x.234: icmp_seq=1 ttl=64 time=0.770 ms

    rtl x.x.x.235
    Ori Destination Gateway Mtr Flags VLAN Duration
    #bi x.x.x.234/31 z.z.z.197 0 UG-D---um--f- rtr-460 0d:18h:52m:35s



  • 2.  RE: GRE tunnel forwarding not working

    Posted 10-16-2018 15:54
    You should create corresponding iproutes at both sides of the tunnel


  • 3.  RE: GRE tunnel forwarding not working

    Posted 10-16-2018 16:18
    That has been taken into account.