From LinuxMCE wiki
1&1 is a german ISP who also provides VoIP services.
Setup of 1und1
Select 1&1 from the Phone Lines link in the web admin and fill out the blanks.
Additional needs if LinuxMCE is NOT your internet router
If you don't have LinuxMCE as your router, you have to add three additional settings manually to the sip.conf in /etc/asterisk/sip.conf In the [general]-section add
localnet=192.168.80.0/255.255.255.0 externhost=<name of your the DNS name of your external IP address> externrefresh=10
Make sure you also to port forward the following ports and protocols to the IP address of the external address of LinuxMCE.
- Port 5060, Protocol udp
- Port 10000-20000, Protocol udp