IP Accounting memory usage

[dbaron]

I would like to use IP accounting to track usage through two ethernet interfaces on a 3620 from a LAN to a high speed network. I have enabled IP accounting on both ethernet interfaces.

The router currently has 24 MB of RAM.

How can I determine how much memory will be allocated/needed if I increase the IP Accounting Threshold to a value as high as 10 or 20 thousand?

Will the router only allow IP accounting to use a percentage of the free memory and not log the maximum number of connections if this memory useage is exceeded?

Any help would be appreciated.

[raymong]

Ip accounting entries range in size from 13 to 28 bytes per entry. You can use the "ip accounting-threshold" global configuration command to set the maximum number of accounting entries to be created.

The accounting threshold defines the maximum number of entries (source and destination address pairs) that the router accumulates, preventing IP accounting from possibly consuming all available free memory. This level of memory consumption could occur in a router that is switching traffic for many hosts. "Overflows" will be recorded; see the monitoring commands for display formats. The default accounting threshold of 512 entries results in a maximumn table size of 12928 bytes.

[wkumari]

You may want to look at using netflow instead of IP accounting. It is much more flexible and powerfull and is less of a RAM hog.....

Warren.

[dbaron]

Thanks for the replies; I now can calculate the memory needed.

I looked at netflow and you are correct, it also is quite granular and it displays the port numbers of traffic as well which is a plus. Problem is that I plan on monitoring traffic flows over some other 2500 series routers with an 11.x version of IOS. i don't think netflow is an option on these routers. Please correct me if I am wrong.