how to manually create a 6in4 tunnel

I'm doing some IPv6 codig for a client and needed to setup a bunch of 6in4 tunnels.

Thre are many ways to do this through distribution init scripts (Debian, Fedora), but I wanted something less permanent and more dynamic for testing.

The procedure can be summarized in these steps:

• create a tunnel mytun between local 1.1.1.1 and remote 2.2.2.2

  ip tunnel add mytun mode sit local 1.1.1.1 \
                  remote 2.2.2.2 ttl 64 dev eth0
  

• give the local end an address

  ip addr add dev mytun f8c0::1.1.1.1/64
  

• bring up the tunnel

  ip link set dev mytun up
  

And here is a script that builds both ends of the tunnel: mk6in4tun

./mk6in4tun 2.2.2.2
### tunnel topology
    [f8c0:69bd::1.1.1.1] 1.1.1.1 (eth0) <======> (???) 2.2.2.2 [f8c0:69bd::2.2.2.2]

### local setup ###
    sudo modprobe ipv6
    sudo ip tunnel add tun69bd mode sit local 1.1.1.1 remote 2.2.2.2 ttl 64 dev eth0
    sudo ip addr add dev tun69bd f8c0:69bd::1.1.1.1/64
    sudo ip link set dev tun69bd up
    sudo iptables -I INPUT -s 2.2.2.2 -d 1.1.1.1 -p 41 -j ACCEPT

### remote setup ###
    sudo modprobe ipv6
    sudo ip tunnel add tun69bd mode sit local 2.2.2.2 remote 1.1.1.1 ttl 64 
    sudo ip addr add dev tun69bd f8c0:69bd::2.2.2.2/64
    sudo ip link set dev tun69bd up
    sudo iptables -I INPUT -s 1.1.1.1 -d 2.2.2.2 -p 41 -j ACCEPT

### taredown instructions ###
    sudo ip tunnel rem tun69bd