ip forwarding solution

I have a linux(fedora 6) box as a gateway device for my network.
Additionaly I have a router to the internet at 192.168.10.250 which is
off the eth0 interface. The 10.0.0.0/8 network lives off the eth1
interface. This is my lab machine. On the other end of the cable for
interface eth1(10.0.0.0/8) network cable is another linux box. I have
ip_forwarding on and successfully working. Using the linux box as a
gateway any 192.168.10.0/24 pc can ping the 10.0.0.0/8 network and
everything is as exspected.
The problem that I cannot figure out is If I unplug the second linux
box on the 10.0.0.0/8 network and connect a Linksys WRT54G router
instead(10.0.0.252), then I cannot ping that router from the
192.168.10.0/24 network. From the gateway machine pings are successful.
But for some reason when the packets are forwarded the router won't
reply. I've tried both the linksys wrt54g with the dd-wrt firmware and
a linksys befsr41 router to no eval. I have sniffed the wire and the
packets are being forwarded but is seems the routers are not replying.
Has anyone experienced this problem?
Thanks for your help.

On 31 Dec 2006, in the Usenet newsgroup comp.os.linux.networking, in article
<(E-Mail Removed) .com>, (E-Mail Removed) wrote:

>The problem that I cannot figure out is If I unplug the second linux
>box on the 10.0.0.0/8 network and connect a Linksys WRT54G router
>instead(10.0.0.252), then I cannot ping that router from the
>192.168.10.0/24 network. From the gateway machine pings are successful.
>But for some reason when the packets are forwarded the router won't
>reply.

Networking is a 'two way street'. The boxes on 192.168.10.0/24 have to
know how to send packets to 10.0.0.0/8 by using the FC6 box as a gateway
to that network - and boxes living on 10.0.0.0/8 have to know that the
192.168.10.0/24 network is reachable using the eth1 interface of the FC6
box as a gateway. Packets do not follow the trail of bread-crumbs back
to the origin. ALL computers have to know how to send packets to everyone
else.

>I've tried both the linksys wrt54g with the dd-wrt firmware and
>a linksys befsr41 router to no eval. I have sniffed the wire and the
>packets are being forwarded but is seems the routers are not replying.

And the routing table of the Linksys looks like...

Old guy

Ok I figured it out.
This was the routing table as it was setup from the gui. The default
gateway was the fc6 box yet it still didn't work.

~ # ip r
192.168.0.0/24 dev eth1 proto kernel scope link src 192.168.0.12
10.0.0.0/8 dev br0 proto kernel scope link src 10.0.0.252
127.0.0.0/8 dev lo scope link
default via 192.168.0.1 dev eth1
default via 10.0.0.101 dev br0

All I had to do was manually add a route as you suggested. And it
works.

~ # ip r
192.168.0.0/24 dev eth1 proto kernel scope link src 192.168.0.12
192.168.10.0/24 via 10.0.0.101 dev br0
10.0.0.0/8 dev br0 proto kernel scope link src 10.0.0.252
127.0.0.0/8 dev lo scope link
default via 192.168.0.1 dev eth1
default via 10.0.0.101 dev br0

So now my question is why wasn't the default route used. Using the gui
on the router I entered the default gw now there are two this was
problem most likely.

Good day




Moe Trin wrote:
> On 31 Dec 2006, in the Usenet newsgroup comp.os.linux.networking, in article
> <(E-Mail Removed) .com>, (E-Mail Removed) wrote:
>
> >The problem that I cannot figure out is If I unplug the second linux
> >box on the 10.0.0.0/8 network and connect a Linksys WRT54G router
> >instead(10.0.0.252), then I cannot ping that router from the
> >192.168.10.0/24 network. From the gateway machine pings are successful.
> >But for some reason when the packets are forwarded the router won't
> >reply.
>
> Networking is a 'two way street'. The boxes on 192.168.10.0/24 have to
> know how to send packets to 10.0.0.0/8 by using the FC6 box as a gateway
> to that network - and boxes living on 10.0.0.0/8 have to know that the
> 192.168.10.0/24 network is reachable using the eth1 interface of the FC6
> box as a gateway. Packets do not follow the trail of bread-crumbs back
> to the origin. ALL computers have to know how to send packets to everyone
> else.
>
> >I've tried both the linksys wrt54g with the dd-wrt firmware and
> >a linksys befsr41 router to no eval. I have sniffed the wire and the
> >packets are being forwarded but is seems the routers are not replying.
>
> And the routing table of the Linksys looks like...
>
> Old guy

On 1 Jan 2007, in the Usenet newsgroup comp.os.linux.networking, in article
<(E-Mail Removed). com>, (E-Mail Removed) wrote:

>This was the routing table as it was setup from the gui. The default
>gateway was the fc6 box yet it still didn't work.
>
>~ # ip r
>192.168.0.0/24 dev eth1 proto kernel scope link src 192.168.0.12
>10.0.0.0/8 dev br0 proto kernel scope link src 10.0.0.252
>127.0.0.0/8 dev lo scope link
>default via 192.168.0.1 dev eth1
>default via 10.0.0.101 dev br0

"Houston, we got a problem here."

>All I had to do was manually add a route as you suggested. And it
>works.

>So now my question is why wasn't the default route used.

_WHICH_ default?

>Using the gui on the router I entered the default gw now there are two
>this was problem most likely.

default route: If you want to go to 'a', use route A. If you want to
go to 'b', use route B. If you want to go to 'c', use route C. If "A',
'B', or 'C' won't take you where you want to go, use route D. If "A',
'B', or 'C' won't take you where you want to go, use route E. So do you
use route D, or E to get to 'f'?

If two (or more) default routes with the same metric exist (see the
output of the command /sbin/route -n), the kernel will use the _LAST_
one that was declared. - figuring that you changed your mind, but forgot
to remove the "old" one. If the metric differs, the route with the lower
metric is chosen.

Old guy