Hello,
it's my first time OpenBSD problem: I setup a network configuration with IPsec
and a GRE tunnel. There is an IPsec connection between a local loopback
interface (lo1) and a remote loopback interface (dummy0 on a Linux box). The
gre interface uses these loopbacks as tunnel src/dest. Following output shows
OpenBSD config:
[EMAIL PROTECTED]:~# ifconfig -A
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33224
inet 127.0.0.1 netmask 0xff000000
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x6
le1: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
address: 00:60:b0:fb:a4:f8
inet6 fe80::260:b0ff:fefb:a4f8%le1 prefixlen 64 scopeid 0x1
inet 213.xx.xx.xx netmask 0xffffff80 broadcast 213.xx.xx.127
le2: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
address: 00:60:b0:cd:3d:15
inet 193.xx.xx.xx netmask 0xffffff80 broadcast 193.xx.xx.127
inet6 fe80::260:b0ff:fecd:3d15%le2 prefixlen 64 scopeid 0x2
pflog0: flags=0<> mtu 33224
pfsync0: flags=0<> mtu 2020
enc0: flags=0<> mtu 1536
lo1: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33224
inet 192.168.254.7 netmask 0xffffffff
gre0: flags=9011<UP,POINTOPOINT,LINK0,MULTICAST> mtu 1450
physical address inet 192.168.254.7 --> 192.168.254.1
inet 192.168.253.18 --> 192.168.253.17 netmask 0xfffffffc
[EMAIL PROTECTED]:~# uname -a
OpenBSD openbsd.my.domain 3.7 GENERIC#50 i386
My problem is to change MTU of gre tunnel. I tried several values, but
everytimes the same result :-( The tunnel works until less then 1376 bytes have
to be transferred. A MTU of 1376 works between a Cisco router an that Linux box,
so I would think, 1376 bytes should also work for OpenBSD / Linux connection.
[EMAIL PROTECTED]:~# ifconfig gre0 mtu 1376
ifconfig: SIOCSIFMTU: Invalid argument
[EMAIL PROTECTED]:~# ifconfig gre0 mtu 1400
ifconfig: SIOCSIFMTU: Invalid argument
[EMAIL PROTECTED]:~# ifconfig gre0 mtu 1450
ifconfig: SIOCSIFMTU: Invalid argument
Any ideas ? Neither FAQ nor mailing list archives / Google showed a solution.
best regards
Christian Felsing
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