Routing question
Ben Boulanger
ben at blackavar.com
Fri May 9 14:08:48 EDT 2003
On Fri, 9 May 2003 pll at lanminds.com wrote:
> DEVICE=eth0 DEVICE=eth3
> ONBOOT=yes ONBOOT=yes
> BOOTPROTO=none BOOTPROTO=none
> IPADDR=10.241.35.18 NETWORK=10.241.37.0
> NETMASK=255.255.255.0 IPADDR=10.241.37.70
> NETWORK=10.241.35.0 NETMASK=255.255.255.0
> BROADCAST=10.241.35.255 BROADCAST=10.241.37.255
> GATEWAY=10.241.35.1 GATEWAY=10.241.37.1
Yup, so pull that GATEWAY out and put it in /etc/sysconfig/network
instead... I imagine that's been touched on already.
> # netstat -rn
> Kernel IP routing table
> Destination Gateway Genmask Flags MSS Window irtt Iface
> 10.241.35.0 0.0.0.0 255.255.255.0 U 40 0 0 eth0
> 10.241.37.0 0.0.0.0 255.255.255.0 U 40 0 0 eth3
> 127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
> 0.0.0.0 10.241.35.1 0.0.0.0 UG 40 0 0 eth0
>
> With this configuration, everything *should* route out eth3, however,
> I can't seem to get this to work properly. One NIC responds, but not
> the other. In this case, eth0 reponds to pings from off these subnets
> (i.e. if I ping from 168.159.31.9), but not eth3.
Everything will route out eth0, everything for the 10.241.37.0/24 net will
route out eth3, but nothing else.
> If I add a second default route for the .37 subnet, like this:
>
> # netstat -rn
> Kernel IP routing table
> Destination Gateway Genmask Flags MSS Window irtt Iface
> 10.241.35.0 0.0.0.0 255.255.255.0 U 40 0 0 eth0
> 10.241.37.0 0.0.0.0 255.255.255.0 U 40 0 0 eth3
> 127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
> 0.0.0.0 10.241.37.1 0.0.0.0 UG 40 0 0 eth3
> 0.0.0.0 10.241.35.1 0.0.0.0 UG 40 0 0 eth0
While not broken, this results in your default route being out eth3, which
is the closed network, with no egress points, right? What -should- happen
is that if eth3 drops for some reason, your eth0 default route will take
over since eth3's routes leave.
If you want to get to either NIC from either subnet, you're going to have
to either route across the linux box or make sure the two networks can
talk independent of the linux box. I take it you mean this:
10.241.35.0/24 can talk to 10.241.37.70
10.241.37.0/24 can talk to 10.241.35.18
as well as
10.241.35.0/24 can talk to 10.241.35.18
10.241.37.0/24 can talk to 10.241.37.70
You want all traffic to route out eth0 (35.0/24) with the
exception of 10.241.37.0/24.
If you turn on IP forwarding, does it act as you would like?
--
"Only two things are infinite, the universe and human stupidity,
and I'm not sure about the former" -- Albert Einstein.
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