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Old 01-11-2004, 06:43 AM   #1
Machiaveli
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Help with collisions ext. Nic


I have a large amount of collisions on my external (eth0) nic. I've been trying to solve this problem for months without success.

My configuration-

Red Hat 8.0 running as firewall and router.
ADSL connection to a Swedish ISP using DHCP.
3 clients connected to the network. Running XP on all.
Realtek 8139c chip (eth0)
3com905(A) (eth1)
100mbit Switched internal network

Here is a screen from my ifconfig-

eth0 Link encap:Ethernet HWaddr 00:10:A7:1E:08:56
inet addr:213.64.53.*** Bcast:213.64.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:139266954 errors:0 dropped:0 overruns:0 frame:0
TX packets:145134862 errors:0 dropped:0 overruns:0 carrier:0
collisions:12921377 txqueuelen:100
RX bytes:81166585 (77.4 Mb) TX bytes:855932251 (816.2 Mb)
Interrupt:10 Base address:0x2000

eth1 Link encap:Ethernet HWaddr 00:10:4B:95:58:6E
inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:450556153 errors:0 dropped:0 overruns:0 frame:0
TX packets:483510641 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:3368802879 (3212.7 Mb) TX bytes:2325677969 (2217.9 Mb)
Interrupt:11 Base address:0x2080

mii-tool reports the following-

eth0: 10 Mbit, half duplex, link ok
product info: vendor 00:00:00, model 0 rev 0
basic mode: 10 Mbit, half duplex
basic status: link ok
eth1: negotiated 100baseTx-FD, link ok
product info: National DP83840A rev 1
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok

This is what I've done so far, tell me if I've missed something (not in this particular order)-

* Reinstalled OS (too many times)
* Switching places between the cards. Tried EVERY combination.
* Tried other cards with the same chip (but with other revisions)
* Tried ALL combinations of 3com905A -B and -C chips together with various RTL8139 chips. 2 3com cards generate errors instead of collisions (go figure)
* Set IRQ manually. (Yes every possible combination)
* Tried every combination in mii-tools.
* Replaced every TP cable.
* Tried using a twisted TP cable between one of my clients and the server.
* Tried using different drivers for the 8139 chip.
* Switch my modem from Alcatel to Nokia.
* And finally when I got bored and pissed - Build a whole new computer. (No reinstallation though.)


I have a friend, using the same modem, the same ISP but with a Slackware 4 installation (IPChains) and with 12 million packages he had about 3000 collisions. That tells me there is something very wrong here.

Now, I use Direct Connect (DC, DC++, oDC and so forth) quite heavily but because of all the collisions my d/l speed is nowhere near where it should be. If I just let one of my clients run with a couple of IE windows open I will get 2-3 collisions per minute. If I open Direct Connect I will get 100+ collisions per minute. Back to my friend, I begged him to install Direct Connect on one of his clients just to see the effect, and what do you know -He had a few collisions during the 10 minutes we had it running. (If I'm not mistaken) On top of that he had no problems whatsoever accessing http pages. (Which I do when I use Direct Connect software, it's almost as slow as a regular modem)

So, what could I do about all this?

Any help would be greatly appreciated!

EDIT* Spelling

Last edited by Machiaveli; 01-11-2004 at 06:51 AM.
 
Old 01-11-2004, 10:07 AM   #2
TheOneKEA
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With that many collisions on a broadband interface, I'd have to say that your local exchange is broken quite badly. Unless someone else comes up with another thing you could try, your best bet is to switch providers, or to try to get ahold of someone knowledgeable at your ISP and explain your situation.
 
Old 01-11-2004, 12:16 PM   #3
chort
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What is eth0 plugged into? A hub? The cable modem? Please post the brand and model of each piece of hardware involved (i.e. what is "outside" eth0 between you and your Internet provider).

By the way, something sounds wrong with both your friend's setup and yours. There is no way you should ever be seeing that many collisions, especially on your Internet link! If your configuration turns out to be OK (waiting on the info I requested above) then I'd have to say your ISP sucks quite a lot.
 
Old 01-11-2004, 12:25 PM   #4
nidputerguy
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Interesting.. The statement your ISP sucks is not neccesarily accurate. It could be something coming in from the ISP side that they should be monitoring or it could be something such as someone bombarding your connection with packets. I would do some network sniffing. Ethereal is a good package. See where they are coming from. It also might be that your NIC or the DSL router has an interface problem. I'm not an expert but I think it's way to soon to blame the ISP.. You could call them also. Often times they like to help solve probs like this.
 
Old 01-11-2004, 12:26 PM   #5
nidputerguy
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Just thought of something. A lot of these DSL router like mine. Cisco 678. Allow you to view collsions and net statistics on the WAN side. You might try checking that to see if they are only internal or if they are external.
 
Old 01-11-2004, 12:44 PM   #6
chort
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Collisions wouldn't some how "pass through" from the WAN side to the LAN side of a device if both have IPs (i.e. NAT'ing), because that's different collision domains. What we're trying to determine is if this device is a bridge (in which case it's just a layer 2 device passing everything across the wire in both directions), or it it's a problem between the NIC, possibly a hub (some possible device in between), and the modem.

If the problem is local, than it's almost certainly a duplex mismatch.
 
Old 01-11-2004, 01:41 PM   #7
TheOneKEA
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Question

I didn't know that a bridge joined collision domains - I thought it separated them.
 
Old 01-11-2004, 01:50 PM   #8
Machiaveli
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Wow, what a response!

I'll try to answer all your questions here.

TheOneKEA-

I have no possibility to change my ISP, I see your point but living in Sweden in a small town does not have many benefits. It monopoly on the market, monopoly, did I get it right? What I mean is that there is this big corporation that supplies the net all over Sweden, except for some corporations that don't supply any broadband services in my region. I could change my supplier but I'll still end up on the same network since.. you got it - The company I have now let the smaller ISPs use their network. So it's basically the same equipment and speed, and price. Sitting between a rock and a hard place here.
The supportservice do not even answer questions regarding Linux.

chort

The cable is plugged directly in the modem, since it's a standard 0,5mbit ADSL connection it runs on 10Mbit half duplex. 20ft long straight TP cable.
If I change the duplex mode to 10Mbit full duplex the NIC start generating errors instead (but it works). Running on 100Mbit will fail the link. Autonegoation will not succeed either (but it still works) so I usually put it on 10BaseT-HD. The modem is an old Nokia modem, but I've tried with a newer version of the Alcatel Speedtouch Home also.
The NIC is, at the moment a Unex RTL8139D. Running with 8139too drivers. I switched my 3com905A card with that one and I still got collisions, but if I used 2 3com cards the collisions were minimal but the errors were pretty bad. I never got 2 3com cards working, don't know why either. As far as I know my configuration should be in order, although I'm not that familiar with linux, a newbie you might say

nidputerguy

No, it's true, my ISP sucks. Just kidding.
I see your point, getting bombarded with packets. I obtain my IPadress though a DHCP and just now, when I did a brand new installation of RH9, I got a new IPadress so if someone was targeting me it should have stopped, but no.. I still have those damn collisions. There "should" not be a interface problem since I tried so many NICs and two different modems. I'm thinking if there could be some kind of problem with my phoneline. I'll have to call my phone provider and ISP (same place) and have them diagnose any transfer problems.

nidputerguy 2

Sorry to say it's not a router, it's just a modem. It's not possible to access the modem in any way.

chort 2

I can guarantee that the problem is on the "external" side since I was thinking the same thing as you. The best way to test this would be to unplug one client and the server (eth1) from the switch and just run a twisted pair cable in between, said and done earlier. I still had collisions, sorry to say.

I really appreciate you guys posting here. This is driving me mad!
I apoloqize for any spelling errors.
 
Old 01-11-2004, 02:06 PM   #9
Machiaveli
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Just to given a "live" example. I just ran a Direct connect software for exactly 1 minute. Have a look here.
For those of you that don't know what DC is, it is a file-sharing program. I understand that there could be some collisions, maybe even alot of collisions since you are connected to a hub with 1200 other people and downloading and uploading at the same time but.. well, have a look. Even if I don't run this file-sharing program I get about 2-3 collisions per minute. That don't seem normal to me.

This is the "pre" Direct connect output from ifconfig-

eth0 Link encap:Ethernet HWaddr 00:10:A7:1E:08:56
inet addr:213.64.53.** Bcast:213.64.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:16466 errors:0 dropped:0 overruns:0 frame:0
TX packets:19225 errors:0 dropped:0 overruns:0 carrier:0
collisions:1278 txqueuelen:100
RX bytes:7141402 (6.8 Mb) TX bytes:12467747 (11.8 Mb)
Interrupt:10 Base address:0x6000

eth1 Link encap:Ethernet HWaddr 00:10:4B:95:58:6E
inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:116204 errors:0 dropped:0 overruns:0 frame:0
TX packets:188467 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:20046558 (19.1 Mb) TX bytes:253413683 (241.6 Mb)
Interrupt:11 Base address:0x2040

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:84160 errors:0 dropped:0 overruns:0 frame:0
TX packets:84160 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:6492119 (6.1 Mb) TX bytes:6492119 (6.1 Mb)

And this is the "post" Direct connect output from ifconfig-

eth0 Link encap:Ethernet HWaddr 00:10:A7:1E:08:56
inet addr:213.64.53.** Bcast:213.64.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:19152 errors:0 dropped:0 overruns:0 frame:0
TX packets:23271 errors:0 dropped:0 overruns:0 carrier:0
collisions:1553 txqueuelen:100
RX bytes:7862378 (7.4 Mb) TX bytes:16194968 (15.4 Mb)
Interrupt:10 Base address:0x6000

eth1 Link encap:Ethernet HWaddr 00:10:4B:95:58:6E
inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:122174 errors:0 dropped:0 overruns:0 frame:0
TX packets:193664 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:23988385 (22.8 Mb) TX bytes:257297017 (245.3 Mb)
Interrupt:11 Base address:0x2040

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:84958 errors:0 dropped:0 overruns:0 frame:0
TX packets:84958 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:6546614 (6.2 Mb) TX bytes:6546614 (6.2 Mb)

What do you think?

I'll try a shorter cable for the modem and move it to a different location just to see if there might be some electrical interference of some sort.
 
Old 01-11-2004, 04:07 PM   #10
chort
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Quote:
Originally posted by TheOneKEA
I didn't know that a bridge joined collision domains - I thought it separated them.
Doh! Of course you're correct. A bridge will join broadcast domains, but separate collision domains.

So quite obviously, the problem is with the link to the modem. ISP is off the hook (although perhaps they can be blamed for shoddy modems if it is the modem's fault)!
 
Old 01-11-2004, 04:09 PM   #11
TheOneKEA
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Talking

I thought so

So the final answer is: get a new modem? It sounds like you're suggesting that the modem's Ethernet transceiver is broken somehow, or that it's missing part of IEEE 802.3's CDMA/CS implementation. Right?
 
Old 01-11-2004, 04:35 PM   #12
chort
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Ahem, so with the cable plugged directly into the modem, and as you've said you already tried using different media settings but they didn't work... You're getting a link, so it's not a problem of using straight-through cable vs. cross-over. I'm extremely surprised that switching modems did not correct this problem. Usually media compatibility problems are the fault of old/non-standard hardware.

It's either the NIC, or the modem. Now I strongly suspect that the modem will do 100Mbit/full duplex (all the broadband devices I've had recently did) so I'm leaning towards the NICs. Are you using ISA NICs, or PCI? See if you can beg, barrow, or steal an Intel Pro/100 PCI NIC (8255[5|7|9] chipset) and try that out as your external interface. I'll bet that will solve the problems.

Another poing is that the 3c905As use PIO mode, while 3c905C uses DMA (more efficient). If you want to stick with 3Com, try a 905C instead.
 
Old 01-11-2004, 04:39 PM   #13
Machiaveli
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Quote:
Originally posted by TheOneKEA
I thought so

So the final answer is: get a new modem? It sounds like you're suggesting that the modem's Ethernet transceiver is broken somehow, or that it's missing part of IEEE 802.3's CDMA/CS implementation. Right?
I'm afraid that it's not the modem's fault. I own two different brands of modems and both of them show the same amount of collisions. One old Nokia modem and a newer Alcatel modem.

I'm beginning to think it might have something to do with the lenght of the cables and or interference from other cables, it might even be my phoneline. Previously I had my router in a closet near the modem, now I have it under my TV, right beside another computer and a receiver. It might be the cables running to my speakers that are scrambling the signal somehow. I also have a longer TP cable now, 10ft was the original cable, this one is 20ft. But in all seriousness, if that were the case, why don't I have collisions on my internal network? Hmm.

I used Freesco as a router with only a floppy, never had a problem as far as I know, no collisions, no errors, not anything except some problems with portforwarding. It held 2 3com cards too

The good news is that I left my computer alone for an hour and didn't have one single collisions, so that also rules out anyone targeting me with packets, but as soon as I refreshed the page to see if anyone replied to my post I got 3 collisions. I'm waiting for a friend to call with a Intel Pro100 card. I'm willing to try a completely new card.

As soon as my back feels better I'll move the server closer to the modem and switch to some shorter cables. Even though they should, not have any problems, theoretically.

More suggestions?
 
Old 01-11-2004, 04:51 PM   #14
Machiaveli
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Quote:
Originally posted by chort
Ahem, so with the cable plugged directly into the modem, and as you've said you already tried using different media settings but they didn't work... You're getting a link, so it's not a problem of using straight-through cable vs. cross-over. I'm extremely surprised that switching modems did not correct this problem. Usually media compatibility problems are the fault of old/non-standard hardware.

It's either the NIC, or the modem. Now I strongly suspect that the modem will do 100Mbit/full duplex (all the broadband devices I've had recently did) so I'm leaning towards the NICs. Are you using ISA NICs, or PCI? See if you can beg, barrow, or steal an Intel Pro/100 PCI NIC (8255[5|7|9] chipset) and try that out as your external interface. I'll bet that will solve the problems.

Another poing is that the 3c905As use PIO mode, while 3c905C uses DMA (more efficient). If you want to stick with 3Com, try a 905C instead.
The modem will not link with anything over 10Mbit, If I were to try I'll end up with no link and I would even have to restart my server since the /etc/init.d/network restart OR ifconfig eth0 up OR mii-tool -r eth0 commands would not work, believe me, I tried it.

You believe it's the NIC but I have tried atleast 3 different 3com905a cards. 3 3com905b cards and 1 3com905c card and 2 differerent NICs with RTL8139 chipset. All NICs are PCI, I have a couple of old ISA 10mbit 3com NICs but I never got them working. I'm also thinking of trying an old 10Mbit PCI card, if I were to find one.

As to the Intel card, you beat me to it Hopefully I'll have one here tomorrow.
 
Old 01-11-2004, 05:10 PM   #15
Machiaveli
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This is what happens on 10Mbit full duplex-

eth0 Link encap:Ethernet HWaddr 00:10:A7:1E:08:56
inet addr:213.64.53.** Bcast:213.64.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:27784 errors:9 dropped:0 overruns:0 frame:0
TX packets:32018 errors:0 dropped:0 overruns:0 carrier:0
collisions:1557 txqueuelen:100
RX bytes:11397549 (10.8 Mb) TX bytes:20525041 (19.5 Mb)
Interrupt:10 Base address:0x6000

No more collisions, but errors instead.

Auto-negotiation (same as 10Mbit half duplex)
Will do this-

eth0 Link encap:Ethernet HWaddr 00:10:A7:1E:08:56
inet addr:213.64.53.** Bcast:213.64.53.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:27784 errors:9 dropped:0 overruns:0 frame:0
TX packets:32018 errors:0 dropped:0 overruns:0 carrier:0
collisions:1557 txqueuelen:100
RX bytes:11397549 (10.8 Mb) TX bytes:20525041 (19.5 Mb)
Interrupt:10 Base address:0x6000

The collisions were generated during the time when my NIC was using both autonegotiation and 10Mbit half duplex.

100Base-Tx FD will do this-

eth0: 100 Mbit, full duplex, no link
eth1: negotiated 100baseTx-FD, link ok

100Base-Tx HD will do this-

eth0: 100 Mbit, half duplex, no link
eth1: negotiated 100baseTx-FD, link ok

Does this information help anyone?
 
  


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