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I am trying to establish a GRE tunnel on a GW running Linux (V2.6.39.3). The network topology is as following:

local:

  • PC_A is connected to a GW
  • PC_A is represented by a dedicated RND (routed network device) VLAN in the GW host
  • GRE tunnel object is created on the GW host
  • erouter0 iterface is the GW interface to WAN

remote (GRE server):

  • erouter0 iterface is the GW interface to WAN
  • GRE tunnel object is created on the GRE server host

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< LOCAL >>>>>>>>>>>>>>>>>>>>>>>>>>> <= Remote
PC_A <===> VLAN interface <===> GRE tunnel interface <====> erouter0 <== Internet ==> erouter0 <==> GRE tunnel

  • PC_A: 192.168.2.20
  • VLAN interface : 192.168.2.1
  • GRE tunnel (local) - ? (not sure if an IP address is mandatory)
  • erouter0 (local) - 10.139.39.59
  • erouter0 (remote) - 10.139.39.148
  • GRE tunnel (remote) - ? (not sure if an IP address is mandatory)

I was using the following procedure in order to create the GRE tunnel on the local side:

  1. ip tunnel add gretun0 mode gre remote 10.100.39.148 local 10.100.39.59 dev erouter0
  2. ip link set dev gretun0 up
  3. ip rule add iif l2sd0.2 table 4
  4. ip route add table 4 default dev gretun0

** As can be noticed, I didn't set an IP address for the GRE tunnel (is it neccessary???)

Problem:

Once generating Iperf UDP traffic from PC_A to the GRE server, trafic doesn't reach its destination. Moreover, once analyzing the traffic which goes through the relevant interfaces using tcpdump I could only observe packets which reach the local RND VLAN interface but they never reach neither the GRE tunnel interface nor the local erouter0 interface.

I was trying to figure out whether the problem is related to an incorrect configuration which I used but till now I couldn't find the root cause for the issue.

I appreciate yours kind suggestions/assistance.

Thanks, Oren

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