Date: Thu, 8 May 1997 14:31:10 PDT From: Bill Fenner <fenner@parc.xerox.com> To: fenner@parc.xerox.com, tom@sdf.com Cc: danny@panda.hilink.com.au, freebsd-hackers@freebsd.org, smc@servtech.com Subject: Re: FTP Performance Message-ID: <97May8.143111pdt.177486@crevenia.parc.xerox.com>
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> Yes, many sites block most if not all ICMP. Any way to disable mtu
>detection?
The best way is probably to set an MTU on your default route; that
way you can add routes to all the destinations towards which MTU
discovery does work. (e.g. if MTU discovery didn't work through my
firewall, I might add a route for 13/8 that does not have an MTU
specified, and a route for default that does have an MTU).
Use "route change default -lock -mtu 576" (or something similar)
to change (and lock) the MTU on the default route.
I just configured my system this way; if I do "route get" on a system
inside my network, it says:
route to: 13.1.100.239
destination: 13.0.0.0
mask: 255.0.0.0
gateway: 13.2.116.250
interface: ep0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
16384 16384 0 0 0 0 1500 0
but if I "route get" somewhere else, it says:
route to: 204.216.27.18
destination: default
mask: default
gateway: 13.2.116.250
interface: ep0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
16384 16384 0 0 0 0 576L 0
Note the MTU and the presence of the L flag.
Bill
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