[Xorp-users] Virtual interfaces in GNU/Linux

[Pavlin Radoslavov]

> The output using ip addr is:
> 
> 1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>     inet 127.0.0.1/8 scope host lo
>     inet6 ::1/128 scope host
>        valid_lft forever preferred_lft forever
> 2: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
>     link/ether 52:54:00:12:34:86 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.1.10/24 brd 192.168.1.255 scope global eth1
>     inet 192.168.13.1/24 brd 192.168.13.255 scope global eth1:1
>     inet6 fe80::5054:ff:fe12:3486/64 scope link
>        valid_lft forever preferred_lft forever
> 3: sit0: <NOARP> mtu 1480 qdisc noop
>     link/sit 0.0.0.0 brd 0.0.0.0
> 
> What do you think?

You have a single network interface (eth1) with two IP addresses.
For multicast routing purpose, this counts as a single interface.
If you have the limitation of only one physical network interface,
but you want to have a multicast router with several network
interfaces, then you need to create virtual interfaces/tunnels such
as GRE tunnels, OpenVPN tunnels, VLANs, etc.

If you don't have much experience with tunnels setup, I'd recommend
to start with OpenVPN (http://openvpn.net/). It is quite portable
and easy to configure. E.g., you could just run a pair of
commands like the following on both sides of a tunnel:

openvpn --local 10.6.0.2 --remote 10.9.0.2 --ifconfig 30.30.30.1
        30.30.30.2 --dev tun0
openvpn --local 10.9.0.2 --remote 10.6.0.2 --ifconfig 30.30.30.2
        30.30.30.1 --dev tun0

FYI, you could use openvpn even across a NAT because it is TCP/UDP
based.

After that you need to use the virtual tun0 interface as one of the
interfaces on the XORP router.

Regards,
Pavlin