Re: Automatically setiting mtu
Hi David
Thanks for reply - and explanations.
> You can set the MTU on an interface from /etc/network/interfaces:
>
> iface eth0 inet static
> address 10.20.30.53
> netmask 255.255.255.240
> broadcast 10.20.30.63
> gateway 10.20.30.49
> mtu 1460
This would be ideal except, my interfaces section here is set to dhcp,
not static - I have tried to see if I can get away with using it with
dhcp, but alas the man page is correct.
>
> > After a bit of googling the only way, out of many, that seems to
work on
> > this box is to delete the default route and use the route command to
> > reinstate it with the mss parameter.
>
> You could probably do that too; is this a particularly complicated
> router machine?
Nah - this box doesn't route at all, but its default route is set to
BOXNAME, which acts as a dhcp server, and gateway to the internet.
At the moment I manually:
route delete default
route add default gw BOXNAME mss 1454
but I often work in the box from off site and don't want to have to do
this.
>
> > I've experimented with the option interface-mtu parameter in
> > dhclient.conf
>
> In my experience that option is completely ignored; it *might* work if
> the DHCP server is configured to send it and the client is configured
> to receive it, but there's no guarantees.
Phew - not just my imagination
>
> > Anyone ever had to play with this to get through the cursed ms
> > internet sharing reigiem?
>
> (!) My (uninformed) impression is that that was just a NAT, which
> shouldn't require resetting your MTU. You might run Debian on your
> gateway machine instead; it's much more configurable, and much easier
> to find out what exactly is going on. 'apt-get install ipmasq' should
> get you going for straightforward things.
>
> What exactly *is* your configuration here?
This is a network of 5 home pc's all running XP Prof. and one debian
box. The
internet gateway is one of the XP boxes doing the 'network sharing
thing' i.e. NAT. The built in 'firewall' in XP port forwards so that
ssh, incoming ftp, postgres and others are all forwarded to the debian
box.
When we first set up the XP network with the ADSL connection on the
gateway, there was all sorts of problems with the NAT machines (all XP
and win98 at the time) using the internet - a bit of googling revealed
we had to set the MTU to 1454 (a windows registry setting).
The debian machine is a relative new arrival and has always had
problems reaching the net through BOXNAME. We figured that perhaps we
had to do the samething for debian as we did for xp, a bit of googling
and here we are now, using route to add the mtu value with the mss
parameter, but wanting something more elegant and automatic.
I've also installed iproute as Jan suggested in previous post, but
haven't had a chance to play, and not sure that it can improve things
any more that they are.
Thhanks for your reply and taking the time to read this
Glenn
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