2 computers - can ping router, but not each other?

blorg

I've got two computers (1 laptop, 1 deskop) and a wireless router (Netgear DG824M). Both computers are XP Pro. Network setup is 192.168.0.1 (router), .2 (desktop), .3 (laptop). I'm using DHCP on the router with reserved IPs.

Both PCs can ping the router and see the internet, no problem. I can ping also each PC from the router. However they can't ping each other! (Obviously nothing else between them works either). I do have another problem with dropouts, but don't think this is related, this seems to be completely software-related, while the dropout problem seems to be hardware-related.

I have port forwarding set up on the firewall so that I can connect in through terminal services to the desktop - while connecting to 192.168.0.2 doesn't work, connecting from the laptop through the external IP address often 'wakes things up' and the computers can suddenly see each other.

Everything works normally if I plug the computers into the router through wired ethernet. We have the same router in the office, same IP address range, if that makes any difference (my laptop is connected up to that during the day - I'm thinking caching of routing information or something - although ipconfig /renew doesn't help). Any ideas?

MiCr0

regarding pinging each other:

if you do a traceroute from one system i assume its getting as far as the router - and not just getting lost on the first hop?

Sleipnir

have you tried stopping the firewall services on both?

blorg

These two PCs are on an internal network, behind the firewall on the router. There aren’t any personal firewalls on the PCs, and XP’s Internet Connection firewall is switched off for the wireless adapters also (I’ll try removing it from the dial-ups also, which I no longer use).

I didn’t run a traceroute at home because it is a LAN – there shouldn’t be any routing involved. The router should only appear in a traceroute if I am going outside my local network – I mentioned pinging the router to demonstrate that there is a working physical connection between both the PCs and the router/AP at all times.

I’ll try it anyway, in case the router is jumping on the internal addresses and trying to route them, but it should be simply acting as an access point for local addresses, and shouldn’t appear in the results at all. This is confirmed at work (same router, at 192.168.0.1):

C:\>tracert 192.168.0.126
Tracing route to rfc1918.space.should.not.be.used.on.publicips [192.168.0.126]
over a maximum of 30 hops:
1 2 ms 2 ms 3 ms rfc1918.space.should.not.be.used.on.publicips [1
92.168.0.126]
Trace complete.

I’ll confirm at home, and let you know. Thanks for taking the time to make the suggestions!

blorg

This is a typical traceroute:

Tracing route to rfc1918.space.should.not.be.used.on.publicips [192.168.0.2]
over a maximum of 30 hops:
1 * * * Request timed out.
2 * * * Request timed out.
...
15 * * * Request timed out.
16 * * 11 ms rfc1918.space.should.not.be.used.on.publicips [192.168.0.2]
Trace complete.

E.g. it will eventually decide to connect (same result can be achieved with ping 192.168.0.2 -t). But as you can see it's not being routed.

It'll then work fine for a while and then disappear again. If I RDP (terminal services) in using the external IP, this generally wakes everything up and I can see 192.168.0.2 from .3 again. I can stay on terminal services through the external IP, while the internal connection drops again (pinging the other 192.168... computer from either one times out). In the remote terminal services case, I am presuming that the packets are being routed by the router (traceroute to the external IP just goes to the router however, it's only the RDP port that is forwarded).

After the internal (192.168...) connection drops, if I cancel out of terminal services on the external IP and reconnect, the 192.168..connection comes back up again.

I've completely deleted the dial-up connections that used to use IC Firewall, no good. Any more ideas?

Sleipnir

that is weird. The only thing that can be causing the problem is the router. I'd imagine if you just put a standard switch or a hub in it's place it would work yes?
If so, then there must be something on the router itself that prevents traffic from passing between the two.
Route table being cleared too often or summat like that?
Bit stumped as to why that would be happening to be honest!

MiCr0

it does sound like there's no route on the router to 192.blah from source 192.blah

happydude13

can they both work at the same time

router might only be happy talking to one at a time.