Christopher Penrose wrote:
> I am trying to create a 16 node (netmask 255.255.240.0) subnet with a
> linux box as a router.
>
> I have a i586 running the linux kernel 2.4.13. My distribution is
> Redhat 7.0. I have two EtherExpressPro cards in my machine. I have had
> the same difficulty with a 2.4.5 and a 2.2.x kernel.
[snip]
> When I turn on forwarding as I have above, I can ping the router
> (133.27.179.224 or 133.27.16.221) from a host (133.27.179.226) on the
> eth1 subnet. However, pings are never returned to this subnet host
> (133.27.179.226) if they are bound for hosts on the eth0 network
> (133.27.16.x) or beyond. Furthermore, pings from the linux router
> (133.27.179.224 and 133.27.16.221) to the subnet host (133.27.179.226)
> are never returned.
Sorry, but I didn't really pay attention to this part before.
So you have something like this:
^
|
|
+----+----+ +------+ +------+
| Gateway | | Host | | Host | (existing hosts)
+----+----+ +--+---+ +--+---+
| 133.27.16.1 | |
| | |
------+------+----------------+--------+----- 133.27.16.0/22
|
| 133.27.16.221 (eth0)
+----+----+
| Linux |
+----+----+
| 133.27.179.225 (eth1)
|
------+--------+--------+----------- 133.27.179.224/28
| |
| |
+--+---+ +--+---+
| Host | | Host | (new hosts)
+------+ +------+
> Is there something obvious that I am missing?
Does the gateway (133.27.16.1) have the equivalent of:
route add -net 133.27.179.224 mask 255.255.255.240 gw 133.27.16.221
?
If not, you need to add it somehow. "somehow" could either be by
configuring a static route, or by running a routing daemon (provided
that the gateway is configured appropriately).
The hosts on the 133.27.179.224/28 subnet need the equivalent of:
route add -net 133.27.179.224 mask 255.255.255.240 gw 133.27.179.225
route add default gw 133.27.179.225
The existing hosts on the 133.27.16.0/22 subnet shouldn't need any
changes. Provided that the gateway has the correct routing table,
those hosts should have their routing tables updated by ICMP redirects
from the gateway.
--
Glynn Clements <glynn.clements@virgin.net>
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