Howdy all, i was wondering if anyone has any idea if there is a means by which i can detect GRE link state ?
what i have is two sites each with two very unstable internet links in order to vpn between them i have ipsec tunnels linking each side twice (four ipsec tunnels in total) i then have 4x GRE tunnels over the top of those in order that i have a secured routable VPN this gives me net.vpn0 net.vpn1 net.vpn2 and net.vpn3 finally i run BIRD over the top which works very well, and synchronises routing tables between the two sites, and allows for me to do such fun as # /etc/init.d/net.vpn0 stop and watch all traffic automagically cut over to another link. so far so awesome. however, as i said the internet links are very unstable, and sometimes just blackhole. so what i was hoping to do is just enable keepalives on the gre tunnel. which sadly seems to be cisco only. can anyone suggest a way of detecting if the GRE is not fully connected ? BIRD only fails over if the net.vpn0 device is down (ifconfig up/down) and for the life of me i cannot find how to detect if a GRE tunnel is 'connected', it seems to just blindly send packets to the remote IP. is my only choice to use L2TP instead ? thanks in advance for any suggestions; if anyone would like the configs in order to set this up let me know and i'll reply to list with a mini-howto PS if i'm on the wrong list i'd welcome a friendly push to the correct list
