Router memory question

[rj.remien]

I have several 1721's with the VPN package (48 MB DRAM, VPN module).

One 1721 - show ver = 36864K/12288K bytes of memory. When I do a "show mem" there is a total of 15.6 MB for processor memory and 12.6 for I/O memory. That equals 28.2 MB. This router has memory-size iomem 25 in the config

Another 1721 - show ver = 44237K/4915K bytes of memory. When I do a "show mem" there is a total of 23.2 MB for processor memory and 5.0 for I/O mem. That equals 28.2 MB. There is no memory-size iomem command in the config

Questions:

1. The total for the I/O memory makes sense from the show ver to the show mem command. Where is the remaining 19.8 MB of DRAM allocated from the processor memory pool?

2. Both routers have the same interfaces. Should I allocate the 25% to I/O on the second router?

3. Is there a rule of thumb for the ratio of processor to I/O memory allocation with different interface configs? Any docs?

Thanks,

RJ

[raymong]

You can use the memory calculator for the 2600/3600 to get an idea of how much total memory is needed and how much of that you should allocate for I/O memory.

http://www.cisco.com/cgi-bin/Support/MemCalc/mem-calc.pl