While this packet capture is GREAT and something we all have been waiting for for a long time, you need to be aware of the following limitations:ġ) After the captures have been made upto the number of packets specified (N), or when you exit the capture mode, the NPU needs to be reset. We strongly recommend to always select the reset option after running the monitoring. Note: In some XR releases the NP reset after the execution of "monitor np counter" is optional. We'll discuss the precise COUNTER_NAME and NPU values separately. ![]() With one simple command you can enable the packet capture: When triggering on a true drop counter, this is obviously not an issue. So be careful when selecting a particular counter to trigger on. Because of the capture, we are diverting the packet from the normal forwarding path for display and we are not reinjecting the packet back. That means that if you would trigger on a counter such as PARSE_FABRIC_RECEIVE, which means packets received from the fabric for processing in the egress direction, these packets potentially could have been forwarded. Note that a captured packet will be DROPPED! The output will be in a hexadecimal format, but this is easy to convert into a wireshark format for evaluation and printing (to be discussed later) ![]() Once the packet is determined to be matching a counter set as a trap, the packet is sent to the CPU for formatting and displaying. It allows you to capture packets that are subject to a particular counter (not necessarily a drop counter) when the packet traverses the various stages of processing inside the NPU. What is this all about, in a quick few words, the key things you need to know to get started using the packet capture capability. With the Packet Capture capability that will come in XR 4.3.1 (spring of 2013) you will be able to capture packets for a variety of counters. Until today we didn't ahve a good capability to capture packets outside the PARSE stage of the NPU (and then via heavy engineering commands).
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