gated/routed

[Paul Civati]

Adrian Wontroba <aw1 at stade.co.uk> wrote:

> > I have three routes on this particular machine, one is a static route to 
> > the internet via our default gw, then we have another static route to 
> > network "b" through gateway "b". Finally there is a "static" route to 
> > network "c" though router "c" which has a failover line to it via router 
> > "d", router c is giving out rip1 updates when the main line goes down so 
> > that the server will switch to router d. 
> > Did that make sense?
> 
> Yes, it makes sense.  From my limited experience, I think I too would be
> trying to use routed under these circumstances.  With luck, somebody who
> really understands this will comment on the problems you are having.

Normally I go for putting specific static routes on the default
gateway/router, as it's the simplest solution.  Any hosts trying
to reach your other specific networks (b, c) will go to your default
gateway.

The default gateway/router will know how to get to these networks
and will (unless it has a separate interface) route the packets
back out the interface they came in on.  In this situation the
router will see this as unsatisfactory and so enerate an ICMP
redirect to the originating host, which will automatically
cause routes to be added to the routing table of that host (this
should work for any TCP/IP capable host, unix, Windows, etc).

netstat(1) will show these routes with a 'D' flag as having been
dynamically entered into the routing table:

% netstat -rn
Routing tables

Internet:
Destination        Gateway            Flags     Refs     Use     Netif
[..]
192.168.8.253      10.0.4.4           UGHD        0        4     fxp0
192.168.8.254      10.0.4.4           UGHD        0        0     fxp0
192.168.50.1       10.0.5.37          UGHD        0       22     fxp0
192.168.50.2       10.0.5.37          UGHD        0        6     fxp0

The case in question is slightly more complicated in the need
for failover, thus (probably) the requirement for RIP.  I'm not
sure if you could do something clever with multiple routes to the
same place but with different metrics and how they would work if
at all, some experimentation needed.

Personally I would look into OSPF if I had to go down the RIP route,
as it's much better.

-Paul-