Date: Sun, 13 Apr 2008 12:58:03 -0400 From: Mike Tancsa <mike@sentex.net> To: freebsd-net@freebsd.org Subject: route change and MTU Message-ID: <200804131657.m3DGvuG6039297@lava.sentex.ca>
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This sort of seems like a bug, but not sure
If I had 2 interfaces, one tun1, pppoe with an MTU of 1492, and one
ethernet, a normal MTU of 1500.
if the default route was via tun1, and I did a
route change default <ip of gateway on the ethernet>
the MTU stays at 1492
e.g. on my RELENG_7 box
0[cage]# route add 1.1.1.1/30 64.7.157.1
add net 1.1.1.1: gateway 64.7.157.1
0[cage]# route get 1.1.1.1
route to: 1.1.1.1
destination: 1.1.1.0
mask: 255.255.255.252
gateway: dslborder1.sentex.ca
interface: tun0
flags: <UP,GATEWAY,DONE,STATIC>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu
expire
0 0 0 0 0 0 1492
0
This is correct. The MTU on the PPPoE interface is 1492
0[cage]# route change 1.1.1.1/30 192.168.0.3
change net 1.1.1.1: gateway 192.168.0.3
0[cage]# route get 1.1.1.1
route to: 1.1.1.1
destination: 1.1.1.0
mask: 255.255.255.252
gateway: 192.168.0.3
interface: bge0
flags: <UP,GATEWAY,DONE,STATIC>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu
expire
0 0 0 0 0 0 1492
0
0[cage]# ifconfig bge0
bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
ether 00:10:18:14:15:43
inet 192.168.0.12 netmask 0xffffff00 broadcast 192.168.0.255
media: Ethernet autoselect (100baseTX <full-duplex>)
status: active
0[cage]#
The MTU should be 1500 after the route change no ?
---Mike
--------------------------------------------------------------------
Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike@sentex.net
Providing Internet since 1994 www.sentex.net
Cambridge, Ontario Canada www.sentex.net/mike
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