From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arthur van Leeuwen <arthurvl@sci.kun.nl>
Date: Fri, 06 Apr 2001 14:53:56 +0000
Subject: RE: [LARTC] @home cable modem
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To: lartc@vger.kernel.org

Sorry for not responding earlier, I've been *extremely* busy.

On Fri, 6 Apr 2001, Josh Sides wrote:

> I would like to put 3 different ip addresses that are in three different
> subnets on the same interface. The interface is directly connected to a
> cable modem.  These ip addresses are assigned to me by my ISP.  How do I set
> up the routing on my linux machine so that all three addresses are reachable
> from the internet.

The simple recipe (in pseudocode, hope this is clear enough):

0. put the ip addresses on the interfaces:

for each ip/mask:
    ip address add <ip/mask> dev <device>

1. set up the default routing table:

for each ip/mask:
    ip route add <gw_for_ip> src <ip> dev <device>

ip route add default scope global \
    nexthop via <gw_for_ip1> \
    nexthop via <gw_for_ip2> \
    nexthop via <gw_for_ip3>
    (etcetera)

2. set up policy routing tables for each of the ip addresses:

for each ip/mask:
    ip route add <ip/mask> dev <device> table <table_for_ip>
    ip route add default via <gw_for_ip> table <table_for_ip>

3. set up rules to select the correct outgoing routes

for each ip/mask:
    ip rule add from <ip/mask> table <table_for_ip> \
         prio <arbitrary unique low number>

> Is it possible to setup multiple default routes?

More or less, yes. See in the recipe. :)

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
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