Thanks for the prompt reply. I just need specific WAN cards to cater for the remote sites. I went for the 2851 because there are 2 more sites looming that we are going to connect back to our HQ. Got a couple of 2600 and 1760 which I want to upgrade as well to support voice pass through and QoS. Will also need recommendation on the IOS upgrade as well for this. Thanks

You need to ask telco which interface will they provide, E1 or what else.

Try to get rid of the older routers, today their job is done more efficiently with 1841 or 8161, the latter aslo have full voice features.

I have been using 2801s on 20 mbps well loaded circuits without a problem, that's why I know it's not a problem.

My remote sites currently connected via serial ports x21 interface. We need to upgrade them to 2 megs and pass voice through

Ask the provider if they will give you E1 (preferred) of keep the X21 interface.

Note, I understand you're the end user, recommend you locate a reputable cisco partner or consultant for the job, doing this alone as a non-certified person can cost you a lot of time and frustration.

I don't doubt what you describe is true, but using what type of interfaces and how many?

Reason I ask, I've first hand experience with a 2811 on a full T3 which runs the CPU flat out when it approaches about 20 Mbps (duplex), although with its CEF rating of 120 Kpps, and "average" packet sizes, I would have expected even higher performance.

Considering 4 E1s is only 8 Mbps (16 duplex), and the 90 Kpps CEF rating of the 2801 (75% of a 2811), it should have sufficient CPU for 8 Mbps (as also seems to be true in your 20 Mbps case), yet what's the impact of additional interfaces, different kinds of interfaces, what features might be being used, and actual traffic that will transit the router? Given those considerations, and my experience of the 2811 on a T3, I would still be concerned going as small as a 2801 for four E1s, yet I agree it might work just fine.

If you obtain a 2801, with a guarantee for full value for a trade-up, in case it does not deliver sufficient performance, then I wouldn't be concerned. If you're "stuck" with the purchase, you'll probably want to insure there's sufficient performance.

Again, though, I agree a 2801 might work just fine. Odds, though, of sufficient performace for the 4 E1s improve with the "faster" 2800s.

The problem with "sizing" routers, there's best case and worst case, with real world usually somewhere between the extremes. But, without working with actual production traffic and all feature requirements, it's difficult to estimate exactly where any one instance falls between the extremes even drawing on performance specs and 1st hand experience with the plaform in other situations.

PS:

BTW, there might be(?) a support issue if you have maintenance and you open a TAC case on a router that's being used beyond a Cisco recommendation. Can any one comment on this relative to 2800 series and number of serial interfaces being used?

Thank you all for all your tips and recommendation. I have decided to get a 2811 with a HWIC-4T for my 4 sites. I beleive the default 12.4 IOS should be fine for QoS and VoIP pass through

Price is always a big consideration, but with regard to setting the tone for discussion (it often does, but) . . .

Those "paying the bills" tend to have a tendency to want costs at a minimum (understandably), and so might go too small.

Technical folk often want to have much reserve capacity "just in case" or for some nonspecific "future growth", and tend toward too much.

The goal is to really "right size", i.e. not too small that needed capacity isn't available nor too large that you pay for capacity never used.

Making choice (or approach) on cost, alone, isn't always the best thing, although cost makes much sense if other factors are equal or cost is weighted such that you might value some features more than others.

PS:

Also on costs . . .

Many look at just initial purchase (lease) price and fail to also consider on-going other costs, such as maintenance, power or cooling costs.