Cogent 100 meg and 3550

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Aug 4th, 2008
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Cogent is handing me off a 100 meg circuit and am wondering if my 3550 will handle. I'm told it will but need the IP Services firmware. I currently have an 1841 handling it and I don't know if I getting all of the throughput.

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Joseph W. Doherty Mon, 08/04/2008 - 16:36
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Ethernet wire rate for 100 Mbps, with 64 byte packets, requires 148,809 pps. Double that for full duplex.

An 1841, within the router performance sheet, is documented as having 75,000 pps within fast/CEF switching. So, it's unlikely the 1841 has sufficient performance to substain 100 Mbps. (What's the CPU usage look like?)

The various 3550 models, within the switch performance sheet, are documented from 6,600,000 pps to 17,000,000 pps, which should provide the necessary raw performance.

Whether the 3550 "will handle" the circuit might also depend on what features you require since it's possible the 1841 offers some features not available on the 3550s.

sjonessha Mon, 08/04/2008 - 20:15
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Yeah thats what I thought. My 3550 is an EMI image and I could upgrade that to the IP services firmware. Thanks.

sunjoseph Thu, 11/06/2008 - 18:43
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I just did the same cogent and 100 meg circuit. which router did you choose and were you able to configure the "serial IP" as well as ip block?

sjonessha Sat, 11/08/2008 - 19:18
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I am using a 3550 with the EMI image. My network engineer did it without the Advanced IP services firmware. We hand off a full class C. All of our customers have a static IP.


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