Two little network annoyances...

[_xxx_]

I have the following config:
DSL modem/router --> WLAN router --> 2 PC's

DSL modem is configured as following: firewall on, all needed ports forwarded to WLAN router, static route, DHCP off (tried it with DHCP on as well but didn't change anything).

WLAN router as DHCP for the both PC's, firewall off, static routes etc. Both PC's get their IP from DHCP and these are also correct.

I can't get the two PC's to connect to each other ("missing permission to access the network" is the message box I get). I see the network and both PC's. Pinging works fine, so the connection is there. Ipconfig also shows that everything is as it should be.

The second problem is that the port forwarding on my DSL modem/router seems to be working incorrectly. Even when I plug the machines directly into it, eMule's port test shows that there's no direct connection with other clients possible ("You can acces the network only through servers, check your firewall/router settings" or such).

Strange: if I turn off the firewall, I can't access the net at all

Both machines have no problems with internet access, though. Only with the little home network.

Any ideas? Any help is appreciated...

 

[JBark]

A couple ideas...

Are they Windows XP machines with the windows firewall running? That could be why you can't connect to any shares on the other machines. You have to enable that option in the firewall settings.

Does the DSL modem/router have a DMZ setting? If it does, put your 2nd router's IP address in there, then everything that comes in should get forwarded right on to the 2nd router. Turn on the firewall on your 2nd router, then you should be able to use the port forwarding settings on your 2nd router. I don't know if this actually works, but it sounds nice in theory.

 

[Frank]

Yes, using the DMZ from the first router might do the trick.

Your problem is NAT. If you have 2 routers that both do Network Adress Translation (which they both do), the adress can't be resolved anymore.

If you only have 1 IP adress on the outside, that means you've got a different network with it's own range on the inside. To be able to track which computer communicates with what computer at the outside, the router uses different ports.

So, if computer 1 makes a http connection (port 80) with some outside computer, and computer 2 does the same with another one, the router picks a port above 16k for the second one and makes a connection between that port (say, 20000) and port 80 on the outside computer.

At that moment we have this:

pc 1: 192.168.0.1
pc 2: 192.168.0.2
router (your external IP adress, example): 64.64.64.64
connection 1: 192.168.0.1:80 <-> 64.64.64.64:80 <-> x.x.x.x:80
connection 2: 192.168.0.2:80 <-> 64.64.64.64:20000 <-> y.y.y.y:80

That way, the router can determine if an incoming packet is meant for pc 1 or 2.

When you have 2 routers doing that, it should work, theoretically. But it almost never does, unless you use professional routers.

The solution: get rid of one router, or attach the second one to the DeMilitarized Zone of the first router (attached to the internet connection). That means, that it won't use NAT for that connection.

 

[_xxx_]

No SW firewall running, tried that all.

I could set DMZ on the DSL router, but it changed nothing. I also tried turning both firewalls off or forwarding 1-65535 both TCP and UDP, but nothing changed...

 

[Frank]

I think it mostly doesn't work because both routers keep a list of routes and ports, and things that are allowed for those. I have been angry many times about those stupid things not just doing what I asked of them, but making up their own mind about it. Like Microsoft. ;-)

But, that doesn't help you. And it didn't help me, most of the time. I know how you feel.

It is rather very annoying, that you cannot get plain modems anymore for cable or ADSL, unless you want to pay for the professional stuff. All of them have a build-in router, that you cannot disable! GRRR.

I rather have a plain modem and use my own router. But, alas, that isn't an option. So, you're stuck with just using a single router that has the correct modem built in most of the time.

 

[DemoCoder]

It's not a linksys router is it?

 

[_xxx_]

Hey! That's the idea! I have my old plain modem somewhere, I'll try that.

But why does the home network work incorrectly?

It's a D-Link dsl-router and U.S. Robotics MaxG WLAN-router.

 

[stevem]

I might suggest you try updating the firmware to the latest available for both the Dlink & USR although sometimes newer firmware can be worse.... Then power down both routers & PCs. First power the DSL modem/router. Wait a few mins. Then power the WLAN/router. Wait a few mins. Then power on the PCs.

If still no go, try enabling DHCP/NAT on one router only (via DMZ if that's the only option). Disable SPI. I assume you've enbled MS client & file & printer sharing? Enable a shared dir on each of the PCs. Simple filesharing or not shouldn't matter. Enable fileshare access through the software firewalls (if WinXP). Try enabling common accounts on both PCs. I had one PC that would always respond to a ping request. Toggling ICMP echo request, reboot, toggle, reboot, fixed the problem...

There's an eMule list of working routers somewhere. See if yours is on it. You may need to play around with port forwarding & limiting connections (for stability). The best SOHO router I've found to date has been an old PIII running Linux/smoothwall...

Also try simplifying the problem. First get the PCs working via the WLAN router only. Then connect the DSL modem to the network for WAN access. Then tackle any P2P issues.

Edit: Try this. Enable DHCP/FW, etc for your DSL modem/router. Disable DHCP for your WLAN/router. Do not use the WAN port on this router. Connect everything via the LAN side. It will now work only as an AP. Check local IPs, subnets etc.

 

[YeuEmMaiMai]

I have a router and a switch with PCs directly on the router and some on the switch. I would make sure that your router is set up to allow all of your PCs on a certain IP range to be on the "Internal network"

 

[Frank]

Edit: Try this. Enable DHCP/FW, etc for your DSL modem/router. Disable DHCP for your WLAN/router. Do not use the WAN port on this router. Connect everything via the LAN side. It will now work only as an AP. Check local IPs, subnets etc.

Very good idea! I'll try that next time, when wireless is the main point of the second router.

 

[suryad]

If I understand your problem correctly try using the wizard in XP to set up the home network. I did and it worked right away.

 

[_xxx_]

Thanks for your hints guys!!!

Port forwarding for eMule etc. works fine now, I messed around with the firewall a bit until it finally worked.

The network still doesn't really work, I sometimes get it going and sometimes not.

EDIT:

Got it all working now. The network problem was Zone Alarm. Although I set it up to allow the connection, it blocked the file and printer sharing service. Forgot to enable that

Now all is working fine, again thanks very much for your help!!!