Routing frustrations

[Alex Beamish]

Hi,

If you have servers a, b and c,

  [a] --- [b] --- [c]

and you are having problems getting a and c to talk to one another,
then you need to make sure the following things are true.

1. a has to know that it needs to get to c via b, usually by telling
it which network connection to go through;

2. b has to permit IP forwarding;

3. c has to know how to get back to a, usually by telling it which
network connection to go through;

4. the relevant interfaces on a, b and c need to be up and running; and

5. the ports that you're using on a, b and c shouldn't be blocked by
clever firewall rules.

Good luck.

Alex Beamish

On 7/20/05, psema4 <psema4-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> I have a minimal FC1 box acting as router:
> eth0 (external) 10.20.30.250/24
> eth1 (internal) 192.168.1.25/24
> 
> If ping (or ssh) is run from the router, I can see (and access)
> machines on the internal network through eth1.
> 
> Machines inside the internal network however cannot ping or
> (seemingly) otherwise access eth1 on the router.
> 
> Here's the output from iptables and route.  Any suggestions or
> pointers would be most appreciated - this is driving me absolutely
> nuts.  :)
> 
> Thanks,
> -Scott
> 
> (PS - actual addresses/ranges have been changed to equivalent addresses/ranges.)
> 
> [root at anheg]# iptables -L
> Chain INPUT (policy ACCEPT)
> target    prot opt source             destination
> 
> Chain FORWARD (policy ACCEPT)
> target    prot opt source             destination
> 
> Chain OUTPUT (policy ACCEPT)
> target    prot opt source             destination
> 
> [root at anheg]# route
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
> 10.20.30.0 * 255.255.255.0 U 0 0 0 eth0
> 127.0.0.1 * 255.0.0.0 U 0 0 0 lo
> default 10.20.30.8 0.0.0.0 UG 0 0 0 eth0
> 
> --
> - SGE
> --
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