Linux / Auto Sense 1

[verit]

My home network has 3 main systems
1. SuSE 8.1 with a Linksys 10/100 NIC Card
2. WindowsXP with a Netgear 10/100 NIC card
3. Smoothwall v2.0 (Linux based firewall)

All work well when the systems are connected to an old 10baseT hub. If I replace the hub with a switch (netgear) or a router (Linksys Cable/DSL) and connect at 100baseT none of the systems can ping or communicate.
By changing the network layout I can get the router to work by connecting it directly to the Internet instead of using the Smoothwall firewall but this is not a prefered solution.

The problem may be related to the AutoSense setting of the NIC cards. I know how to change the setting on the XP machine but not on Linux machines. The SuSE configuration tool lets you set the Interrupt Level and memory address but does not provide the 10/100, half/full duplex, autosense settings. Any ideas?

 

[krale]

My home network has 3 main systems
1. SuSE 8.1 with a Linksys 10/100 NIC Card
2. WindowsXP with a Netgear 10/100 NIC card
3. Smoothwall v2.0 (Linux based firewall)

---All work well when the systems are connected to an old 10baseT hub. If I replace the hub with a switch (netgear) or a router (Linksys Cable/DSL) and connect at 100baseT none of the systems can ping or communicate.

Are there active filters present blocking data transmission? This should work.

---By changing the network layout I can get the router to work by connecting it directly to the Internet instead of using the Smoothwall firewall but this is not a prefered solution.

I know that the Netgear routers can do that, but are you saying you were able to successfully connect using your 10/100 router?

---The problem may be related to the AutoSense setting of the NIC cards. I know how to change the setting on the XP machine but not on Linux machines. The SuSE configuration tool lets you set the Interrupt Level and memory address but does not provide the 10/100, half/full duplex, autosense settings. Any ideas?

Lets not jump to hardware conclusions quite yet. First, go get Ethereal (either for windows or Linux) and do a packet sniff while trying different things on the network. Try pinging with the same machine you're using ethereal on. Work your way out. Check ifconfig on your Linux machines to make sure IP is correctly set up.

I really doubt it's a autosense issue, or ifconfig wont get anything. Usually, when AS fails, your hardware defaults to 10BT Half duplex. Please let Tek-Tips members know if their posts were helpful.

 

[verit]

krale,
I'll try to answer some of the questions you raised.

I don't think I have any active filters set except perhaps inbound from the Internet on the smoothwall firewall system.

I took the Linksys router completely out of the network. It used to just route traffic directly to my cable modem just fine when I had the XP system and a second windows2000 system connected to it. I'll try it again at some point but even if that works it does not act as a firewall. Plus, with the firewall acting as a router and a second router in the network things start to get a little more complicated so I tried to eliminate it as a potential point of failure.

The hub works perfectly fine but connects all systems at 10Mb. There are no configurable options on the switch. When moving the cables from the hub to the switch it shows that the systems are connecting at 100Mb but when I attempt to ping to or from any one of the systems I get a Host Unreachable message.


ifconfig does show things are working correctly with hardware and IP addresses assigned. I am using all static IP addresses as follows:
10.10.1.1 = firewall's internal address (the external address is dynamically assigned by my ISP and works fine)
10.10.1.2 = XP system
10.10.1.3 = SuSE/Linux system
All NIC cards are assigned with the appropriate address.
10.10.1.1 is assigned as the gateway address in the XP and SuSE systems. (could this be the problem? If so, I don't see why.)

Your suggestion about using the Ethereal sniffer is the best one I've heard thus far. I've never used a sniffer before so hopefully it won't be too difficult to figure out.
Thanks for your help.

Verit

 

[krale]

Ethereal can "snioff" the data on the line directly. Doesnt matter if it's IP, IPX(novell), ICMP (ping).. If it goes over that line, you SHOULD be able to see it.

When you try to ping an IP address, a few things happen. I'll go over what happens (and what to watch for)..

1: Open ethereal on your Ethernet card (eth0 on linux)
2: do a: ftp _IP_ . This will invoke a set series of discovery actions.

{Discovery Actions}

3:Your computer sends from broadcast MAC address to tell them what MAC address _IP_ address is.*README
4:The computer that recognizes itself as _IP_ number tells your computer "My MAC address is XYZ".
5:Your computer will add to a cache table MAC to IP temporially (usually 60 seconds).

{end discovery actions}

6: Now your computer knows PHYSICALLY where _IP_ is located. Now it can commence with FTP negoiation.
7: Enter FTP stuff here..... ;-)

*README: A MAC address is a Media Access Control. Simply said, it's a unique serial number for your ethernet card.The number is 48 bits big, and usually shown as 01:23:87:b2:ce:f0 .

When I mean on #3 when I say broadcast MAC, is it sends through mac FF:FF:FF:FF:FF:FF.

Also to answer your gateway question.. Shouldnt be an issue.


> are connecting at 100Mb but when I attempt to ping to or from any one of the systems I get a Host Unreachable message.

Watch this CAREFULLY when you repeat this under Ethereal watching. Still, something seems fishy with that router.

Hopefully, you can diagnose the symptoms. If we can get the results, we can probably come up with what's wrong, and how to fix that. Just basic scientific method ;-) It's a PITA though... Please let Tek-Tips members know if their posts were helpful.

 

[verit]

Krale,
Once again, I appreciate your tips and wanted to give you an update. I decided to back up to some very basic configuration.
First, I returned the switch to compusa and decided to make my network function with the Linksys router or else drop back to the hub configuration.
To test the router, I pluged the network port directly into the cable/modem then configured the XP machine to communicate through the router to the Internet without a problem. Then I added the the SuSE linux box to the hub and when that didnt seem to work, I tried ethereal.
It was clear at that point that packets were broadcast correctly but nothing was coming back.
Next I swapped out the NIC card in the SuSE box and was able to ping the router but it was very very slow return packets.
The wiring from the linux box to the router is different in that it first attaches to a wall plate, which then is connected across a room to another wall plate, which then connects to the router through a second patch cable. Needless to say, one of the problems that I had was a noisy patch cable problem. (That's what I get for building my own wiring.)
I think that the 10Mb connection masked the problem but at 100Mb things were clearly broken.
I may have a secondary routing problem but have not had a chance yet to continue testing. Thanks for all your help thus far and I'll keep you posted.

 

[krale]

Krale,
>Once again, I appreciate your tips and wanted to give you an update. I decided to back up to some very basic configuration.

I just like weird erors, as it also helps my skills too ;-)

>First, I returned the switch to compusa and decided to make my network function with the Linksys router or else drop back to the hub configuration.
>To test the router, I pluged the network port directly into the cable/modem then configured the XP machine to communicate through the router to the Internet without a problem. Then I added the the SuSE linux box to the hub and when that didnt seem to work, I tried ethereal.
It was clear at that point that packets were broadcast correctly but nothing was coming back.

Yep. I was hesitant to say it was the hub/switch. I've only seen 1 go bad, and that was lightning strike. ALso, did you try different ports on the router, and different cables?


>Next I swapped out the NIC card in the SuSE box and was able to ping the router but it was very very slow return packets.

If you check out ifconfig, it'll tell errors too. Usually when you see an abnormal amount of errors (not collisions) It's a wire problem (or a hellishly trashed nic).

>The wiring from the linux box to the router is different in that it first attaches to a wall plate, which then is connected across a room to another wall plate, which then connects to the router through a second patch cable. Needless to say, one of the problems that I had was a noisy patch cable problem. (That's what I get for building my own wiring.)

There's nothing wrong with building your own cables. Go walk into an office supply store, and they _gouge_ you on even 10 ft cables. I just went to a bulk store and ordered 1000 ft of cat6. I can put a phone jack and a ethernet jack on each panel. And since it's twisted pair, little crosstalk.

Still, as a reccomendation for testing patch cables, if you have a volt meter (an led and a bettery will do), test the contunity of each line. You may want to test if there's wires touching (by checking adjacent lines). If you get any signal, cut and recrimp.

>I think that the 10Mb connection masked the problem but at 100Mb things were clearly broken.

The higher the density, the more corruption you'd get from bad lines.

>I may have a secondary routing problem but have not had a chance yet to continue testing. Thanks for all your help thus far and I'll keep you posted.

A way I do testing on a segemnt is by going to console and issuing a continual ping (in windows you need a argument for it). If you want to load-test a server (and line for errors) issue a ping _ip address_ -f on a linux machine. Taken from the manual (ping)

Flood ping:

Outputs packets as fast as they come back or one hundred times per second, whichever is more. For every ECHO_REQUEST sent a period ``.'' is printed, while for ever ECHO_REPLY received a backspace is printed. This provides rapid display of how many packets are being dropped. Only the super-user may use this option. This can be very hard on a network and should be used with caution.

(end manual segment)

This function will flood the computer with about all it can process. However, you can then do a ifconfig and see what kind of data loss you're getting. Packets lost (the period) isnt bad. Neither are collisions. If you get errors, check the wiring.

Hopefully, I',m helping. ;-) Please let Tek-Tips members know if their posts were helpful.