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New Member

LAG on network. Need URGENT Help


For the past two days, we have been having a really strange lag. There is a lag between our switch and our providers and they are directly linked via a Fiber SC line in the same datacenter. We usually get <1 ms lag, now it goes up to 60 MS sometimes. We have a Cisco Catalyst 3550 48 port SMI, our provider has a similar 3550...

What changed:

We had about 20 Vlans in the switch along with routing 20 Vlans to other Layer2 switches. Recently we got our new block of IP to assign the servers so we are giving EACH server a subnet of 8 IP's. Therefore we created 400 VLANS along with routing 350 of them (meaning we now have 350 different gateway IP addresses on the 3550). Now we DO NOT know if this is related with the lag but kind of happened around the same times we started routing those Vlan's (nothing happened really when we just created without routing them).

We do not think they are related as that switch should be able to take more than that and in terms of bandwidth we are only at 100 MBPS.

We have no idea what can be causing this, but do you think what I wrote above with the vlans can create such a problem??

Please let me know ASAP

MUCH appreciated


Re: LAG on network. Need URGENT Help

That could very well be your problem , have never heard of anyone putting that many routed vlans on a 3550 switch , its probably almost out of memory . I would be hesitant to put that many on a 6500 . What do you mean we are only at 100 mbps ? Are you talking between you and the isp ? It's not the bandwidth its that the 3550 has to keep track and allocate memory for 400 vlans along with spanning tree and other things. What does show proc cpu show and a show proc memory . That must be one big config if you defined that many.

New Member

Re: LAG on network. Need URGENT Help

Thank you for helping me, here is the output of what you asked, CPU and MEMORY, I would greatly appreciate the help.

KEEP IN MIND that it is not CONSTANT lag, during night time sometimes it is normal, even during daytime, its intermitent. Even pinging the providers router which is physically connected to us, we sometimes get <1 ms and sometimes 40 MS even if it is directly connected to us, that is why it is intermitent, comes and goes...

ATTACHED TEXT FILE is the output of the requested commands, hope someone can help me ASAP. Thanks

New Member

Re: LAG on network. Need URGENT Help


Any reply on this?