Delay between networks

Unanswered Question

Hi folks,

My network is growing on, then, I made some diferent new networks, ( LAN1-Current), ( LAN2), etc, I want to manage these networks with a 1750 Cisco Router Fastethernet interface, but I notice I have a delay between LAN1 and LAN2 around 45ms (ping), and the aplication bad performace is noticeble.

Questions are:

Is that delay normal?

Do I need to make any configuration on router?

if that delay is normal, I would prefer exchange my network to Class B whit 23 bits mask.

Can somebody help please???


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Joseph W. Doherty Tue, 03/25/2008 - 16:42
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The problem you might be seeing is the 1750 doesn't really provide LAN bandwidth level routing performance, especially at 100 Mbps.

pnicolette Tue, 03/25/2008 - 17:52
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How many devices do you have on each separate network?

If you want one large "flat" network, consider configuring broadcast storm control on all your switch ports.

To route between separate networks, a Layer 3 switch (such as Cisco 3550 or newer) will give MUCH less delay than a 1750.

If you want to make sure the 1750 is doing the best it can, see whether methods like Cisco Express Forwarding (CEF) are being used for most packets. show interface statistics can get you started.

pnicolette Thu, 03/27/2008 - 04:52
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You can expect similar performance. My understanding is that routing between physical interfaces and between virtual interfaces (such as trunked VLANs) occurs similarly.

However, combining the traffic from multiple subnets/VLANs into one physical interface may increase congestion and delay, compared to a setup with three or more physical interfaces with traffic flowing among them all.

Note that the same router when it can CEF-switch most packets may handle ten times more traffic than when it has to process-switch most packets. Use show interface stats to get a rough idea of how your 1750 is operating.


Thax a lot for your comments Paul,

you need to know that my diferent networks are connected to the same interface of 1750 router with secondary ip, in fact, it is the defaul gateway for all my networks. /24 200 devices /24 50 devices /24 50 devices

thanx again, any comment will be useful



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