Router Performance - Branch equipment in Datacenter Enviroment

[Tracer Germany]

Hello,

3 Years ago I designed a new Datacenter LAN & WAN Network for a Customer.

He told me the final Size and growing for the next 2 Years and i made several suggestions.

The Smallest Platforms in my Suggestion was 3945E.

But he told me to start with the smallest possible Router Platforms and WAN links.

The idea behind this was to keep the Initial Budget low and to change Router and Links as needed.

So almost all routers expect the VPN HUPs are at the moment 1921/K9.

Now after 2 Years running the Systems without Problems there customer like to start a performance Review for budgeting due to the need to double the User Load.

According to the "small" Router Platform i was expecting the need to Change some or all of them. At least the Internet Routers und Main routers.
I checked CPU, Memory and Interfaces of all of them.
But Memory is Ok and CPU usage are still below 50%. So those "small Branch" equipment seems to work very well in this Datacenter environment.
The Platform 1921 should only be able to handle up to 15Mbit (with Features enabled) but the Routers deliver much more without Problems.
I know that it depends on the Features used like VPN IPS ACLs ect. ....
Some of them are used for Plain Routing with small Tables (Up to 150 Networks) and basic BGP functionality, other ones for Internet Access at 100Mbit (used only 30Mbit average / Peak up to 50Mbit at present)

So my Question is now:
Are there some other Indicators than the CPU & Memory usage who tell us that the Routers may run out of Power?
Or are there some Soft limits that may produce some Problems before CPU & Memory limits are reached?

I don’t seed any Packet drops or any other bad behavior.

What are your recommendations?

Thanks for the Reply!
Tracer

[Joseph W. Doherty]

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Posting

On most small Cisco routers, I would say CPU usage is the key indicator.  However, capacity isn't always linear.  50% current usage may not predict you can handle twice the bandwidth of the same kind of traffic.  (Also, as a general rule, you don't want to average above 75%.)

The attachment, might help you "shop" for Cisco router to meet your future needs.

[Tracer Germany]

Thanks for the answer! and the Document ...

[Leo Laohoo]

I would say that the 3945E is capable of handling 125 Mbps of traffic (two-way traffic of upload AND download) and without any encryption.