Re: Kernel Routing sequence

From: Henrik Nordstrom
Date: Mon Aug 15 2005 - 04:50:53 EST


On Mon, 15 Aug 2005, Al Boldi wrote:

interface in the same network range is generally a bad idea, but
works reasonably provided one uses a subnet of the other.

For all practical purposes it is unusable, since the subnetting-scheme
is hardcoded into the linux kernel. Bummer!

No it is not.

What is hardcoded in any IP equipment is that one IP address should only exist on a single host. You can not easily have the addresses 10.0.1.0-10.0.1.255 on two different networks if there is any direct connection between the two, including a station needing to talk to both networks.

But you can set up a Linux box in such manner that it will work relatively fine in such configuration, but it requires use of policy routing as mentioned before. But even then the locally assigned addresses must be unique. i.e. your 10.0.1.1 address on eth1 must not exists in the 10.x/8 network on eth0, or at a minimum (with proper configuration of your host, see arp_filter in linux/Documentation/networking/ip-sysctls.txt) must not need to talk to your host.

Regards
Henrik
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