Date: Mon, 30 Aug 2004 05:53:47 -0400 From: Skip Ford <skip.ford@verizon.net> To: freebsd-questions@FreeBSD.org Subject: Per-route MTU? Message-ID: <20040830095347.GC587@lucy.pool-70-17-33-17.pskn.east.verizon.net>
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When specifying the MTU of a route, packets larger than the MTU
are still sent...
$ route -n get 10.10.6.1
route to: 10.10.6.1
destination: default
mask: default
gateway: 192.168.1.1
interface: ed0
flags: <UP,GATEWAY,DONE,STATIC>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 0 0 0 0 1492 0
$ sudo ping -D -n -c 1 -s 1472 10.10.6.1
PING 10.10.6.1 (10.10.6.1): 1472 data bytes
36 bytes from 192.168.1.1: frag needed and DF set (MTU 1492)
Vr HL TOS Len ID Flg off TTL Pro cks Src Dst
4 5 00 dc05 e586 0 0000 40 01 7de5 192.168.1.2 10.10.6.1
--- 10.10.6.1 ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss
Why doesn't this host recognize that 1500 is too large of a packet
to send to the default destination based on the MTU of the route
being 1492?
Am I doing something wrong?...or misunderstanding something?
$ uname -r
6.0-CURRENT
$ sysctl -a | grep mtu
net.inet.tcp.path_mtu_discovery: 1
The route's MTU was set using "-lock -mtu 1492".
--
Skip
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