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New Member

Intervlan routing performance

Hi All

Got some performance issues.

If I copy a 300mb file on a lan with 2950's from one pc to a server the file transfer takes around 13 seconds. If I implement router on a stick with a 3620 and do the same file transfer between the pc and server but put them on different subnets and implement intervlan routing, it takes about 1 min 40. An amazing 10 times longer. Tried this on some of are other lans and got the same result. Is it the intervlan routing process that performs poorly or is just that switches are just much faster than routers. What if I didnt use intervlan routing (havent tried this yet) and plugged two 10/100 cards in a 3640 and plugged them into the individual lans, would performance improve seeing as we arent performing intervlan routing.

Any thoughts here would be much appreciated

Best regards

New Member

Re: Intervlan routing performance

what is the speed/duplex setting on the connection between router and switch. do you see any errors on that port ?. Are you using trunking or secondary networkr (secondary ip address) ?

New Member

Re: Intervlan routing performance


Speed/duplex between switch hub - 100 full duplex, and I am using trunking (dot1q). I dont see any errors or have any seconday address's. One thing I have noticed is that if I do a ping between vlans and change the mtu size to say 5000 bytes I will get timeouts, dont think I had this problem when I had two individual cards in the router


New Member

Re: Intervlan routing performance

If you used one Ethernet port per VLAN instead of trunks - you should notice an improvement in performance. This will be dependant upon the number of VLAN's you have because if you had 100 VLAN's you would need an Ethernet interface per VLAN on the router - ie 100 router interfaces which is not practical!

If you have only a few VLAN's it may be worth trying. The reason for the better performance is simple. If you had a 100MB port configured as a trunk (ISL or dot1q) and trunked 4 VLANs over the interface, each VLAN in theory would have to share the bandwidth. Therefore, 100/4 = 25MB of bandwidth per VLAN. If you used a dedicated router port per VLAN (access links instead of trunks) you would have 100MB of bandwidth per VLAN because it would not be sharing bandwidth with any other VLAN's. Also the router would introduce less latency stripping trunk encapsualtion, etc.

This is very theoretical I know but try and see - and let me know how you go on!


New Member

Re: Intervlan routing performance

I have same thing with 3662 router and 2900XL series switch. And I think that the reason is that router can't route packets with FastEthernet speed. Does anybody now how is the routing perfomance on 3660 series routers?

It is interesting that I have pulsating traffic with intervlan routing. Why?

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