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How to solve low memory problems in a Cisco IOS® gateway when used for T.37 store-and-forward fax


Core Issue

Currently, I/O memory is set at a level of available DRAM (10 percent). In many cases, this is a poor allocation of DRAM because in most customer environments I/O memory can be established at much lower portion of available DRAM.

T.37 is a store-and-forward method, and it needs packet memory to store fax messages. This puts a requirement of 2.0 MB of iomem and 8.0 MB of process memory to be free before admitting any T.37 fax call.


This problem is solved by increasing the I/O memory manually. To increase the I/O memory, issue the memory-size iomem percentage command in global configuration mode.

By default, the I/O memory size is 10 percent. It can be increased to 15 percent or more depending on the application that is running. You can issue show memory summary command to verify the memory allocated.

Problem Type

Ask a how to ... question

Fax and modem problems

Fax and Modem Problems

Fax store and forward problems

How to ...

How to ... voice network features

How to ... fax/modem features

Failure Type

Disk or memory issues

When Problem Occurs

Part of fax/modem handshake


T.37 store&forward offramp

T.37 store&forward onramp

Voice Gateways

IOS gateways