View Full Version : [all variants] ip route // source routing policies not (!)always(!) working

March 11th, 2009, 01:09 PM

we use a Maschine with 3 NIC to offer dhcp to two different networks. a third NIC is in a seperate network for maintainance.
The DHCP Server needs this source-routing, which means, that received dhcp-requests will be answered through the same interface they came in. (until they don´t have any ip information yet)

So I setted up the rt_tables:

echo "100 route115" >> /etc/iproute2/rt_tables
echo "101 route56" >> /etc/iproute2/rt_tables
echo „102 route46“ >> /etc/iproute2/rt_tables

And for each interface in /etc/network/interface i added some post-up script:

auto eth0
iface eth0 inet static
post-up /etc/network/if-up.d/jura_src_routing115.sh

Inside this script:

ip rule add from table route115
ip route add default via dev eth0 table route115
ip route flush cache

It defines the gateway for that specific network and tells to use it for this NIC.

The same for all other NIC. And fine! It works like this.
But when I restart the VM it might be, that it just works for one or two interfaces.
After restarting the network (/etc/init.d/networking restart) maybe it works on different combinations (nic1 and nic3; or nic1 and nic2).

ip route shows no differences.

- "Works" means for me, that I can ping adresses in the same subnet.
- The Maschine is a virtual Maschine running on a Ubunt Host with Virtualbox. I wasn´t sure if it is VirtualBox bug, but it doesn´t seam so, because it is possible to run dhcpclient on a "non-working" NIC, and it can send and receive....

Does anybody have an idea how it is possible, that something works sometimes and sometimes not without any changes in the config?????

I´d really appreciate any ideas... I am struggling with this stupid problem since month and I can not find any solution else then try, try try....

March 16th, 2009, 02:29 PM