Nortel Networks NN46110-602 manual Saving captured data, Memory considerations

Chapter 5 Packet capture 109

•A start trigger causes the system to wait for a specific packet before it starts saving packets to the capture buffer.

•A stop trigger causes the system to stop saving traffic in the capture buffer after a specific packet matching the stop trigger is encountered. The packet capture object, however, is not fully stopped. Start trigger can still restart the capture.

A trigger works only for the direction for which the capture is configured. For example, if you enable packet capture for outgoing traffic only, and the type of packet that triggers the capture to start or stop arrives only in incoming packets, the trigger does not work.

You can use triggers with filters. Like filters, triggers never match non-IP frames. The packets that triggered the capture object to start or stop are also captured if they match capture filters.

You can use a start trigger with a stop trigger to capture specific transaction- oriented traffic. If you set both a start and a stop trigger, the start trigger can reenable saving traffic to a capture buffer. You can activate both a start trigger and a stop trigger on the same packet. In this case, only one packet is captured.

Saving captured data

By default, packet capture stops copying data to the capture buffer when the buffer becomes full. To configure a capture object to overwrite the data in the buffer with new data, run the wrapping command.

Use the command capture save to save captured network traffic from the capture buffer in memory to a file on the VPN Router disk. You must stop packet capture before you can save the buffer to a file. (See “Starting, stopping, and saving capture objects” on page 119.)

Memory considerations

The number of packet capture objects that are allocated on a VPN Router depends on the available contiguous memory. When you create a capture object, you can specify the capture buffer size (the default buffer size is 1 Mbyte).

Nortel VPN Router Troubleshooting