GRE link state detection

[Matthias Cramer]

Hi

What routing protocol do you run ? Would it be possible to just lower the hellos in the used
protocoll so it detects a link loss faster ?

Regards

  Matthias

On 05/09/13 17:07, thegeezer wrote:
> 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;
> PS if i'm on the wrong list i'd welcome a friendly push to the correct list
> 


-- 
Matthias Cramer, Erachfeldstrasse 1b, CH-8180 Bülach
http://www.freestone.net
GnuPG 1024D/2D208250 = DBC6 65B6 7083 1029 781E  3959 B62F DF1C 2D20 8250

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