Cisco 2948G-GE-TX lost packet

[Jeremy_Gillet]

Hello,

We recently change our Switch to a 1Gb/s Cisco Switch and eveything seem to be fine until my user start crying at me saying they could not access their email anymore, I'm not sure it's the switch or the computer but my first guess would be the Switch.

Let explain in detail and the test i have done

My network is composed of 1 48port Switch where i connect all my client computer and server on it. 1 router for our WAN and one switch/router for the Local ISP

All my computer and server are updated to the last Ms patch

The problem in detail and some exemple:

First Exemple:

If i lose the connection to the Mail (software) server i also cannot ping the IP addresse of the server, witch i think indicate that there is no problem whith the Software itself.

In the same time an other computer can still ping and access the Mail server and his Mail.

Second Exemple:

Now i got this problem i tried to move it on the other port of the same switch with no better result so i move it on the Switch router and i see an improvement. but still i lost connectivity to the Server time to time.

while i was able to ping the switch router itsel

Exemple 3:

to try to locate what happen when i lose the server i initiate a ping from my computer to the server and to the switch (ping -t) and see what happen when i lose the connection, i have also initiate a ping from the mail server to the switch and to the File server.

The result of this is i never lost packet even when other user report problem to me and the server itself never lost any packet.

we have a small network with not so many load between the server and the client

The configuration of the switch hasn't been changed and only one vlan is enable for the switch

if anyone have any idee (is it from the switch, the computer itself)

Thanks for your help

Best Regards,

Jeremy Gillet

[arvindchari]

Hi Jeremy

If your computers are all patched up neat and tidy, it should not be a problem with the computers themselves.

Are all the computers connected @ 1gbps to the switch ? Are the ports all in auto negotiation mode?

You can try the following:

When the problem occurs, telnet to the switch or console into it and run a "show interface module/port" command to see what kind of errors you are getting off that port (FCS errors perhaps?)

Set the speed and duplex settings of the switchport connected to the server and all ports that seem to be affected by this symptom manually @ 100 mbps full duplex and then test if the problem appears again.

HTH

Please rate posts that help.

Regards

Arvind

[Jeremy_Gillet]

Ok i have switch all the port for the client computer to Full duplex 100 (and i'm wondering why i bought a 1Gb switch :'(

I will see tomorow if it's still happening to my users

Thanks for your help

Best Regards,

Jeremy Gillet

[Jeremy_Gillet]

Here is the result of the command show port on the port connected to the Mail Server

[Jeremy_Gillet]

here is the command show port showing the error (Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize)

for all the port

[arvindchari]

Im sure that you can switch back to 1 Gbps but you need to probably upgrade the cables / reduce crosstalk or some very technical detail like that. What kind of cables are you using currently?

I have experienced cases where cheap quality cables caused several errors, causing me to throttle back to as low as 10mbps after which it would work perfectly fine!

Do revert back if switching down to 100mbps solved the problem atleast temporarily.

Meanwhile check out this link

http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a0080118a51.shtml

which states that

xmit errors (which are most prominent in your case) are indicative that the internal port transmit (Tx) and receive (Rx) buffers are full. A common cause of Xmit-Err is traffic from a high bandwidth link being switched to a lower bandwidth link, or traffic from multiple inbound links being switched to a single outbound link. For example, if a large amount of bursty traffic comes in on a gigabit port and is switched out to a 100Mbps port, this might cause the Xmit-Err field to increment on the 100Mbps port. This is because that port’s output buffer is overwhelmed by the excess traffic due to the speed mismatch between the incoming and outgoing bandwidths.

So its most probably an issue with speed / duplex mismatches.

On the NIC's that are on the computers could you try manually setting the parameters to 1000Mpbs / Full duplex?

Regards

Arvind

[Jeremy_Gillet]

We Use Cat5e Shield from the wall plug up to the server bay, the rest is with normal cat5e cable,

The only thing wish bother me is the way they cable the bay, they removed the shield and the plastic cover from all the cable and plug them like normal except the cable aer uncoil from the begining of the 24port bay up to the end...

Like this (hum i hope you understand this poor quality drawing):

|||| 135

-====|||

246

Most of the computer where quite stable on 1000Mbps / Full duplex (i mean they where not switching fro 1000Mb/s to 100Mb/s and back to 1000Mb/s).

I understand your point about the hight bandwith link but since the server itself got a 1Gb network card and only tranfert a small amount of data to each of those computer it should be ok even if you look at the traffic it seem to be quite far from this problem

Show Traffic

Threshold: 100%

Traffic Peak Peak-Time

------- ---- -------------------------

0% 4% Fri Feb 24 2006, 18:17:37

Anyway it's still not working and i'm wondering what can cause that problem (should i burn the server?)...

Thanks

Best Regards,

[Jeremy_Gillet]

Since we were running at 100Mb/s full duplex and the file server is running at 1Gb/s i made some test to see how the thing was working. so i tried to tranfer 2 file of 480MO each and send them to the file server. it was quite a suprise to see that i was only using 0.50% of my 100Mb/s Bandwitch.

So i tried at 1000Mb/s again with the same file and then it was working at 25% of the capacity wich is a bit more understandable....

I'll try to change our patch pannel and cable it in a better way with the hope to solve this problem.

Best Regards,

[Jeremy_Gillet]

I forgot to say that in 100Mb/s i got a lot more error

Attached is the Show port command with the error for my desktop computer

[arvindchari]

Throttle all devices on your network back down to 100mbps. Having the server at 1000mbps and other devices at 100mbps would only elevate the problem in most cases as the server will try to pump data out at wire speeds.

Also you mention the shielding has been removed. I dont quite understand why your cabling engineers might do this? Removing the shielding would increase crosstalk and since you have only one 48 port switch there is going to be quite a bit of cross talk all over the place!

HTH

Please rate posts that help

Regards

Arvind

[Jeremy_Gillet]

ok will do that and see what happen,

About the cabling guy well i'm not sure he was so knoweldgable about cabling the network since his work was mostly in Telecom (where you only have 2 cable) anyay it seem fine to me at that time since he guaranty to me that he had done the same for our local Internet Provider, but he might have lied also anyway i'll redo the cabling on the patch pannel and see the result

Thanks,

Best Regards,

Jeremy

[Jeremy_Gillet]

I have changed all the port to 100Mb/s and the speed is better (better than when connected at 100 to the server at 1000) between my client and the file server, but i have a lot more error than before.

See my attachement:

Before i had no Single-Col or Multi-Coll in the statistics.

Best Regards,

Jeremy

[Jeremy_Gillet]

It still doing it :''''(

[amit-singh]

Hi,

Which Cat OS you are using on it. Did you try upgrading the Cat OS on the box. Try that and see if that makes any difference.Make sure that you upgrade it to the latest one.

regards,

-amit singh

[Jeremy_Gillet]

i badly don't have access to the update of the Switch firmware/software...