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Router sizing spec

I am curious if there is a design guide regarding Cisco recommended router make/model based on office size (small/medium/large) where the s/m/l relates to number of devices on the office network creating network traffic, i.e. users, servers, printers, voice, wap, etc.....  (don't have numbers for these classifications).

I have a site where there they have approx 300 users/devices, with 4507 distribution sw, connecting up to a 2821 router with 4x T1's bundled (multilink 1).

The WAN connection is near 75%-80% utilize during regular business hrs. No qos currently running.

I'm concerned that, first - the 2821 router for this number of devices and bundled T1's is undersized. Second, seeing output drops on the multilink interface - which I understand could be related to wan congestion - plain and simple.

But we have another site, same scenario, but wan utilization is around 55-65% during reg business hrs - minimal qos is applied on the router multilink 1 interface, but output drops occur as well...even though i might see the multilink 5 min in/out around 50% or the ~6Mb bundle.

Looking for any cisco material that states whether the c2821 is ok, or whether Cisco would recommend another make/model for something of this size and traffic requirement.

thanks

Ed

4 REPLIES
Hall of Fame Super Gold

Router sizing spec

The link below will give you an indication of what kind of router you need based on the WAN link.

http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf

Just a warning, the value express is in HALF duplex and without any encryption.  Half the value and this will give you full duplex OR with encryption.

Take the full value and factor it by 4 and you'll get full duplex AND full encryption.

Hall of Fame Super Gold

Router sizing spec

A 2821 should be fine. An ISR G2 would be better.

Also if you can move away from bundled T1 to Ethernet, that would be a major plus.

New Member

Re: Router sizing spec

Hi Paolo,

Can you elaborate more on your comment about moving away from the bundled T1 to Ethernet please. What is the reasoning or benefits going to Ethernet (think I may know, but want to make sure).

Thanks

Ed Nehring

Super Bronze

Re: Router sizing spec

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Posting

Those that come to my mind include:

  • Less serialization latency
  • No MLPPP processing overhead
  • No MLPPP bandwidth consumption
  • Less processing overhead for moving packet from/to Ethernet L2 frame to/from Serial L2 frame
  • Usually able to obtain, and quickly change, logical bandwidth caps on Ethernet hand-offs
  • Often able to obtain FastEthernet and sometimes GigEthernet hand-offs

PS:

Your 2821 might be okay up to about 20 Mbps (duplex).

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