2524 switch, excessive crc/alignment errors

[John Orme]

Hi,

I have a network with 2 2524 switches, one in the main data centre where the servers connect and there are 5 hubs and 10 10mbit fibres to remote cabinets. There is a 100mbit module to another switch via fibre. I have been having trouble when copying large files from workstation to workstation or from server to workstation. The collision lights come on and the file transferr slows down. The switch logs "Excessive CRC/Alignment errors - see help" and it specifies the port that the workstaion is connected. I have replaced the cables and the network cards and the wall port. We have had a problem in the past on this setup where the entire network has gone down, collision lights on evety device, including remote cabinets and all PC's, the PC's cannot even be used as they run very slowly. Any suggestions would be of great help I am running firmware 4.08

[Jerome Henry]

That's a Mac layer's problem. Check that devices connected to your switch are on auto-negociate speed, or half duplex, and not on full duplex by default. In accordance with 802.3 standard, 2524 switch will not respond properly in that case.
Besides, of course, check that cable length is less than 100m, does not pass close to perturbating electromagnetic sources (for the hub part).
Where does your workstation connect excatly, and is the problem related with only one workstation, or any ?

[Jerome Henry]

By the way, did you check the 5/4/3 rule ? your server and your workstation can be separated by 5 segments max, with 4 hubs max, among which 3 only can be linked to actual machines (the others just links segments). This can alos be a cause for CRC errors (the FCS is then non relevant according to 803.3 spec, and generates CRC/alignments erros too).

[John Orme]

Hi,

I ahve checked for the 543 rule. The switch is central and all the servers are connected directly into it, as is the workstation that is generating the errors. The only bit I am unsure of is the 10 mbis fibre which is connected as follows.
HP 2524
|
3Com 10/100 hub
|
10mbis fibre transceiver in the hub
|
fibre cable to the 10 mbis fibre hub.
|
fibres to the remote switches which are connected with fibre transceivers.

Thanks

[Arimo Laine_2]

Hi.

I'd advise you first to update the switch FW, current rev is F.05.09.

Then make sure that the link settings are same on both ends of the link, so either autoneg on both ends (and on inter-switch links definitely use autoneg) or fixed speed/duplex. This applies also to server / workstation NICs.

There's no 10MB fibre xceiver for 25XX, so I presume you're using media converters. Not necessarily a very good idea, you have to be very careful when setting up the links with those and it doesn't necessarily work as expected.

If the CRC/Alignments come only from the workstation port, check the port status. If it's HDx, you most likely do have a duplex mismatch situation.

If you are using stacking kits and see the errors after FW update, call support.

HTH,
Arimo

[Jerome Henry]

I agree wth Arimo. If your pb is recent, check this duplex negociation issue, if it's always been since this configuration, check FW and fiber.
Good luck.

[John Orme]

Hi,

The 10 mbis fibres are connected via a transceiver in a 3com hub which then goes to a 10 mbis fibre hub and then to the remote locations.

I have had a look on the switch via telnet and I can see how to set the port to duplex etc but I want to check what status it is in first, I have not changed the settings knowingly so I would presume that they would be auto select.

Thanks

[Arimo Laine_2]

Hi.

Let's take it again: There is no 10MB fibre xceiver for 2524 switch. The existing xceivers are 100MB/s and 1000Mb/s. What's the product number of the fibre xceiver you have in the 2524?

I'm very surprised if you have got 10MB/s fibre working with this switch at all... AFAIK the only workaround is to connect TP to a media converter and thereon to the fibre.

Arimo

[Jerome Henry]

And once again auto negociate is fine, half duplex is fine, only full duplex is critical, on both ends, meaning even on your servers or workstations, which are much likely to be full duplex if they are recent !
Good luck.
J

[Morgan Ecklund]

I have a similar problem Excessive CRC/Alignment errors with a 2524 and a 2626. I have checked both sides are set to auto detect sped and duplex. I then changed one of the workstations to fixed 100TX on the switch. I have not seen the problem again today, but this problem is totally intermittant, works for a day or a few weeks then I get the errors. Does the new firware fix any autodetect problems?

[Juergen Lunow]

I have the same problem.(On port 1-12,13-24 are ok ?)

The only thing thats works for me was to replace the switch!

[John Orme]

I threw all the 3com kit in the rubbish and replaced it all with gig fibre and 2524 and 4108 switches, now it all works great and very very fast. Only problems i had were reboots but new firmware fixed that. now we have about 15 fibre connected switches and 2 4108s for the distribution. i never did solve the errors, must have been a compatibility issue with the 3com hubs and other kit.

Thanks :)

[Morgan Ecklund]

So you did install the Firmware update and it did not fix your problem? Fixing the speed/duplex mode did not fix problem. I am having the problems with Win XP and Win 2000 systems with Intel desktop NICs. I changed over to a new drop on the Win XP system have not seen the errors in 24 hours (does not mean anything).

[John Orme]

Upgrading the firmware on the 4108 switches fixed my rebooting problems. I think the collisions were caused by the 3com hubs connected to the HP kit, when I got rid of it all, my problems went aswell. I have not used intel network cards so cant comment on those. Mine are all either IBM on board, 3com 3C905CX-TX-M or the good old EZ2000.

I have had many problems with dodgy cat 5 cabling in the past (we are a machine shop with lots of 3-phase motors and things)I got the cable installers to test and re-terminate my ports and that helped a lot. I think cable is the most important part of a good network and it deserves to have most money spent on it, after all it should last longer than any PC or switch.

Good luck! :)