On Sun, Feb 17, 2002 at 12:08:52AM -0600, Hal Snyder wrote:
> Just a "me too" - we're seeing MTU blackholing due to a gif tunnel
> (MTU 1280) carrying iBGP, and the usual external factors.
> 
> (from memory - this was a couple weeks ago)
> 
> The obvious convenient workaround seemed to be to set the MTU on 
> Ethernet perimeter interfaces to that of the tunnel, but as noted, the
> MSS hint sent during TCP setup by our NetBSD-1.5 zebra routers did not
> decrease after the change. It did not help to delete cloned routes or
> to try to set a per-route MTU.

net.inet.tcp.mss_ifmtu=1
net.inet.tcp.rfc1323=0

but there're problems if you want to use NAT.

--wb