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massive problem with network switch URGENT

Hi all, I have a problem with my network, it seems like everything in vlan 1 on my 3 switches is running very slow, I have ran ethereal, and used my monitoring software on the switch to check errors, bandwidth etc but nothing is showing abnormal, but pinging anthing on the LAN is taking between 300 and 3000ms, is there anything that would cause this???? there is no loops as spanning tree is enabled and not blocking.

please help asap


Re: massive problem with network switch URGENT

Check for broadcast storms. Look at vlan 1 interface for any anomaly. Enable IP accounting/netflow to look for any users sending high volume of traffic.

Post some stats from the switch for us to look at it. How do you know there's no spanning tree issue in vlan 1?



Community Member

Re: massive problem with network switch URGENT

they are some switches that I have just taken over, they are nortel 450T, I normally use cisco so Im new to them, spanning tree is enabled on them and surely if there was a loop it would of been blocked ?? if im using ethereal what should I be looking for ??

thanks a million

Community Member

Re: massive problem with network switch URGENT

Cisco and Nortel deal with Spanning Tree in totally different ways (almost 90 degrees).

Cisco does Per VLAN Spanning Tree as default, Nortel puts all the VLANs in one spanning tree instance by default, as one example.

Cisco includes all VLANs in a trunk port unless EXCLUDED, Nortel EXCLUDES all VLANs ina "tagged" port unless included..

And don't even get started with "etherchannel" vs what Nortel calls "trunking" (link aggregation) and compatibility..

If things were running before and you don't/haven't added/removed/changed VLANs on ports, then this might not be the problem, but if you do, it can create a huge STP loop problem.

I've run into compatibility issues before, and usually, the easiest way to troubleshoot is to not have to go cross-vendor... Other option would be to use access ports (instead of trunk ports) on a single VLAN to link the 450T up to the core, that would eliminate some of the STP agita that can occur.

Good luck --



Re: massive problem with network switch URGENT

Do a show process cpu and show process memory to give you an idea as to what might be causing the slow response. You may also have excessive errors on some ports in VLAN 1 that may be causing excessive retransmits and slowing the network down....Keep us posted....

Community Member

Re: massive problem with network switch URGENT

these are some stats from a port in vlan 1

these are average per sec

InOctets 18,975.19

OutOctets 15,912.68

InUcastPkts 91.53

OutUcastPkts 37.57

InMulticastPkts 44.03

OutMulticastPkts 0.17

InBroadcastPkts 0.54

OutBroadcastPkts 0.08

does this say anything ????

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