[Openswan Users] Changing MTU on a route seems to mess up leftsourceid in a conn definition

Paul Wouters paul at xelerance.com
Sat Sep 16 02:15:14 EDT 2006

On Sat, 16 Sep 2006, Greg Scott wrote:

> /sbin/ip route change dev eth0 mtu 1470

> First, the routes before:
> [root at roseville-fw ipsec.d]# /sbin/ip route show
> aa.bb.cc.32/29 dev eth0  proto kernel  scope link  src aa.bb.cc.33
> dev eth0  proto kernel  scope link  src
> dev eth2  proto kernel  scope link  src

Note the "src" which comes from your leftsourceip=

> Now changing the MTU on the tunnel route
> [root at roseville-fw ipsec.d]# /sbin/ip route change dev eth0
> mtu 1470

Note how you did not specify "src" on the route replacement.

> The routes after:
> dev eth0  scope link  mtu 1470

So it is not there anymore..

> But this ping from the internal interface works...
> (The conn definition is supposed to include the internal interface.)

> [root at roseville-fw ipsec.d]# ping -I
> PING ( from : 56(84) bytes of data.
> 64 bytes from icmp_seq=1 ttl=127 time=65.3 ms

Indeed, because then the "src" argument isnt needed.

So, use:

/sbin/ip route change dev eth0 src mtu 1470

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