On Tue, 11 Oct 2005 14:40:10 +0200 Steve Comfort <steve@xxxxxxxxx> wrote: Hi, I can't understand your diagram as well. :-( Let's suppose you have 2 hosts, host A and host B, each has an outer ("public") and an inner ("local") interface. The outer interfaces have the IP addresses Apub and Bpub respectively, and the inner networks have the address spaces Aloc and Bloc, respectively. Also we make use of another pair of IP addresses, for the tunnel interfaces (10.10.10.1 and 10.10.10.2). Then the right commands would be: host A: ip tunnel add net0 mode gre remote <Bpub> local <Apub> ip address add 10.10.10.1/32 net0 ip link set net0 up ip route add <Bloc> dev net0 host B: ip tunnel add net0 mode gre remote <Apub> local <Bpub> ip address add 10.10.10.2/32 net0 ip link set net0 up ip route add <Aloc> dev net0 If the tunnel works, you can ping 10.10.10.2 from host A (and 10.10.10.1 from host B), if the routing works also, you can ping the other inner network from each host. > I do have a firewall, configured to do NAT on the PPP interface. I have > also tried excluding the destination addresses from being NAt'd but this > didn't make any difference. Just a quick question: you do not filter out GRE (IP protocol 47) on the firewall? (NATing GRE is a bad idea as well - it does not work AFAIK.) And don't forget that the GRE tunnel transmits all the traffic unencrypted, so only use it on a trusted network. (Not even on that.:-) norbi _______________________________________________ LARTC mailing list LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc