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michael
Asked: 2013-05-17 13:26:54 +0800 CST

Ubuntu GRE local ip address, wan ip of router, or ip of ubuntu server

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I have an ubuntu server behind a router that I am configuring to have a GRE tunnel to another remote device across the interwebs.

in the config, I add the line:

pre-up iptunnel add tun1 mode gre local [local ip] remote [remote ip] ttl 255

Since the ubuntu server is behind a router, should the [local ip] be the wan ip of the router? or the actual local ip of the ethernet interface i wish the tunnel to connect through?

The router the server sits behind doesn't say anywhere anything about forwarding GRE 47 to lan devices, so I just DMZ'd the server (no ideal in product, but I am just testing using GRE to allow for multicast discovery from 1 subnet to another)

Here is the full script (with local ip set as lan ip of ubuntu server)

auto tun1
iface tun1 inet static
    address 10.0.33.1
    netmask 255.255.255.0
    pre-up iptunnel add tun1 mode gre local 192.168.33.72 remote x.x.x.x ttl 255
    up ifconfig tun1 multicast pointopoint 10.0.33.2
    post-down iptunnel del tun1
ubuntu

1 Answers

  1. The IP is the IP of the server and not the IP of router.
    So let say you have 1.2.3.4/24 configured on eth0, with 1.2.3.1 being the the default gw/router, then the command would be: 

    iptunnel add tun1 mode gre local 1.2.3.4 remote x.x.x.x ttl y
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