Packet Trace
First Published: August 03, 2016
The Packet-Trace feature provides a detailed understanding of how data packets are processed by the Cisco IOS XE platform, and thus helps customers to diagnose issues and troubleshoot them more efficiently. This module provides information about how to use the Packet-Trace feature.
Finding Feature Information
Your software release might not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the “Feature Information for Packet Trace” section.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
This module contains the following sections:
Information About Packet Trace
The Packet-Trace feature provides three levels of inspection for packets: accounting, summary, and path data. Each level provides a detailed view of packet processing at the cost of some packet processing capability. However, Packet Trace limits inspection to packets that match the debug platform condition statements, and is a viable option even under heavy-traffic situations in customer environments.
Table 21-1 explains the three levels of inspection provided by packet trace.
Table 21-1 Packet-Trace Level
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Accounting |
Packet-Trace accounting provides a count of packets that enter and leave the network processor. Packet-Trace accounting is a lightweight performance activity, and runs continuously until it is disabled. |
Summary |
At the summary level of packet trace, data is collected for a finite number of packets. Packet-Trace summary tracks the input and output interfaces, the final packet state, and punt, drop, or inject packets, if any. Collecting summary data adds to additional performance compared to normal packet processing, and can help to isolate a troublesome interface. |
Path data |
The packet-trace path data level provides the greatest level of detail in packet trace. Data is collected for a finite number of packets. Packet-Trace path data captures data, including a conditional debugging ID that is useful to correlate with feature debugs, a timestamp, and also feature-specific path-trace data. Path data also has two optional capabilities: packet copy and Feature Invocation Array (FIA) trace. The packet-copy option enables you to copy input and output packets at various layers of the packet (layer 2, layer 3 or layer 4). The FIA- trace option tracks every feature entry invoked during packet processing and helps you to know what is happening during packet processing. Note Collecting path data consumes more packet-processing resources, and the optional capabilities incrementally affect packet performance. Therefore, path-data level should be used in limited capacity or in situations where packet performance change is acceptable. |
Usage Guidelines for Configuring Packet Trace
Consider the following best practices while configuring the Packet-Trace feature:
- Use of ingress conditions when using the Packet-Trace feature is recommended for a more comprehensive view of packets.
- Packet-trace configuration requires data-plane memory. On systems where data-plane memory is constrained, carefully consider how you will select the packet-trace values. A close approximation of the amount of memory consumed by packet trace is provided by the following equation:
memory required = (statistics overhead) + number of packets * (summary size + data size + packet copy size).
When the Packet-Trace feature is enabled, a small, fixed amount of memory is allocated for statistics. Similarly, when per-packet data is captured, a small, fixed amount of memory is required for each packet for summary data. However, as shown by the equation, you can significantly influence the amount of memory consumed by the number of packets you select to trace, and whether you collect path data and copies of packets.
Configuring Packet Trace
Perform the following steps to configure the Packet-Trace feature.
Note The amount of memory consumed by the Packet-Trace feature is affected by the packet-trace configuration. You should carefully select the size of per-packet path data and copy buffers and the number of packets to be traced in order to avoid interrupting normal services. You can check the current data-plane DRAM memory consumption by using the show platform hardware qfp active infrastructure exmem statistics command. See the “Configuration Examples for Packet Trace” section for more information about configuring packet trace.
SUMMARY STEPS
1. enable
2. debug platform packet-trace packet pkt-num [fia-trace | summary-only] [data-size data-size ] [circular]
3. debug platform packet-trace punt
4. debug platform condition [ipv4 | ipv6] [interface interface ] [access-list access-list -name | ipv4-address / subnet-mask | ipv6-address / subnet-mask ] [ingress | egress]
5. debug platform condition start
6. debug platform condition stop
7. show platform packet-trace {configuration | statistics | summary | packet {all | pkt-num }}
8. clear platform condition all
9. exit
DETAILED STEPS
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Step 1 |
enable
Router> enable |
Enables the privileged EXEC mode. Enter your password if prompted. |
Step 2 |
debug platform packet-trace packet pkt-num [fia-trace | summary-only] [circular] [data-size data-size ]
Router# debug platform packet-trace packets 2048 summary-only |
Collects summary data for a specified number of packets. Captures feature path data by the default, and optionally performs FIA trace. pkt-num —Specifies the maximum number of packets maintained at a given time. fia-trace —Provides detailed level of data capture, including summary data, feature-specific data. Also displays each feature entry visited during packet processing. summary-only —Enables the capture of summary data with minimal details. circular —Saves the data of the most recently traced packets. data-size —Specifies the size of data buffers for storing feature and FIA trace data for each packet in bytes. When very heavy packet processing is performed on packets, users can increase the size of the data buffers if necessary. The default value is 2048. |
Step 3 |
debug platform packet-trace punt
Router# debug platform packet-trace punt |
Enables tracing of punted packets from Layer2 to Layer3. |
Step 4 |
debug platform condition [ipv4 | ipv6] [interface interface ][access-list access-list -name | ipv4-address / subnet-mask | ipv6-address / subnet-mask ] [ingress| egress]
Router# debug platform condition interface g0/0/0 ingress |
Specifies the matching criteria for tracing packets. Provides the ability to filter by protocol, IP address and subnet mask, access control list (ACL), interface, and direction. |
Step 5 |
debug platform condition start
Router# debug platform condition start |
Enables the specified matching criteria and starts packet tracing. |
Step 6 |
debug platform condition stop
Router# debug platform condition start |
Deactivates the condition and stops packet tracing. |
Step 7 |
show platform packet-trace {configuration | statistics | summary | packet {all | pkt-num }}
Router# show platform packet-trace 14 |
Displays packet-trace data according to the specified option. See Table 21-1 for detailed information about the show command options. |
Step 8 |
clear platform condition all
Router(config)# clear platform condition all |
Removes the configurations provided by the debug platform condition and debug platform packet-trace commands. |
Step 9 |
exit
Router# exit |
Exits the privileged EXEC mode. |
Displaying Packet-Trace Information
Use these show commands to display packet-trace information.
Table 21-2 show Commands
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show platform packet-trace configuration |
Displays packet trace configuration, including any defaults. |
show platform packet-trace statistics |
Displays accounting data for all the traced packets. |
show platform packet-trace summary |
Displays summary data for the number of packets specified. |
show platform packet-trace {all | pkt-num } [decode] |
Displays the path data for all the packets or the packet specified. The decode option attempts to decode the binary packet into a more human- readable form. |
Removing Packet-Trace Data
Use these commands to clear packet-trace data.
Table 21-3 clear Commands
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clear platform packet-trace statistics |
Clears the collected packet-trace data and statistics. |
clear platform packet-trace configuration |
Clears the packet-trace configuration and the statistics. |
Configuration Examples for Packet Trace
This section provides the following configuration examples:
Example: Configuring Packet Trace
This example describes how to configure packet trace and display the results. In this example, incoming packets to Gigabit Ethernet interface 0/0/2 are traced, and FIA-trace data is captured for the first 128 packets. Also, the input packets are copied. The show platform packet-trace packet 10 command displays the summary data and each feature entry visited during packet processing for packet 10.
Router# debug platform packet-trace packet 128 fia-trace
Router# debug platform packet-trace punt
Router# debug platform condition interface g0/0/2 ingress
Router# debug platform condition start
Router# debug platform condition stop
Router# show platform packet-trace packet 10
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
State : PUNT 55 (For-us control)
Start : 597718358383 ns (06/06/2016 09:00:13.643341 UTC)
Stop : 597718409650 ns (06/06/2016 09:00:13.643392 UTC)
Input : GigabitEthernet0/0/0
Destination : 224.0.0.102
Input : GigabitEthernet0/0/0
Entry : 0x8a0177bc - DEBUG_COND_INPUT_PKT
--More-- Input : GigabitEthernet0/0/0
Entry : 0x8a017788 - IPV4_INPUT_DST_LOOKUP_CONSUME
Input : GigabitEthernet0/0/0
Entry : 0x8a01778c - IPV4_INPUT_FOR_US_MARTIAN
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017730 - IPV4_INPUT_LOOKUP_PROCESS_EXT
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017be0 - IPV4_INPUT_IPOPTIONS_PROCESS_EXT
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017bfc - IPV4_INPUT_GOTO_OUTPUT_FEATURE_EXT
--More-- Lapsed time : 680 ns
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017d60 - IPV4_INTERNAL_ARL_SANITY_EXT
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017a40 - IPV4_VFR_REFRAG_EXT
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017d2c - IPV4_OUTPUT_DROP_POLICY_EXT
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
Entry : 0x8a017940 - INTERNAL_TRANSMIT_PKT_EXT
IOSd Path Flow: Packet: 10 CBUG ID: 52
Packet Enqueued in IP layer
Destination : 224.0.0.102
Interface : GigabitEthernet0/0/0
Router# clear platform condition all
Example: Using Packet Trace
This example provides a scenario in which packet trace is used to troubleshoot packet drops for a NAT configuration on a Cisco ASR 1006 Router. This example shows how you can effectively utilize the level of detail provided by the Packet-Trace feature to gather information about an issue, isolate the issue, and then find a solution.
In this scenario, you can detect that there are issues, but are not sure where to start troubleshooting. You should, therefore, consider accessing the Packet-Trace summary for a number of incoming packets.
Router# debug platform condition ingress
Router# debug platform packet-trace packet 2048 summary-only
Router# debug platform condition start
Router# debug platform condition stop
Router# show platform packet-trace summary
Pkt Input Output State Reason
0 Gi0/0/2.3060 Gi0/0/2.3060 DROP 402 (NoStatsUpdate)
1 internal0/0/rp:0 internal0/0/rp:0 PUNT 21 (RP<->QFP keepalive)
2 internal0/0/recycle:0 Gi0/0/2.3060 FWD
The output shows that packets are dropped due to NAT configuration on Gigabit Ethernet interface 0/0/0, which enables you to understand that an issue is occurring on a specific interface. Using this information, you can limit which packets to trace, reduce the number of packets for data capture, and increase the level of inspection.
Router# debug platform packet-trace packet 256
Router# debug platform packet-trace punt
Router# debug platform condition interface Gi0/0/0
Router# debug platform condition start
Router# debug platform condition stop
Router# show platform packet-trace summary
Router# show platform packet-trace 15
Input : GigabitEthernet0/0/0
Output : internal0/0/rp:1
State : PUNT 55 (For-us control)
Start : 1166288346725 ns (06/06/2016 09:09:42.202734 UTC)
Stop : 1166288383210 ns (06/06/2016 09:09:42.202770 UTC)
Input : GigabitEthernet0/0/0
Destination : 224.0.0.102
IOSd Path Flow: Packet: 15 CBUG ID: 238
Destination : 10.64.68.255
Packet Enqueued in IP layer
Destination : 10.64.68.255
Interface : GigabitEthernet0/0/0
Additional References
Related Documents
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Cisco IOS commands |
Cisco IOS Master Commands List, All Releases |
MIBs
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None |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at this URL: http://www.cisco.com/go/mibs |
Technical Assistance
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
http://www.cisco.com/cisco/web/support/index.html |
Feature Information for Packet Trace
Table 21-4 lists the features in this module and provides links to specific configuration information.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 21-4 lists only the software releases that support a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Table 21-4 Feature Information for Packet Trace
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Packet Trace |
Cisco IOS XE 3.10S |
The Packet Trace feature provides information about how data packets are processed by the Cisco IOS XE software. In Cisco IOS XE Release 3.10S, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers. The following commands were introduced or modified:
- debug platform packet-trace packet pkt-num [ fia-trace | summary-only ] [ data-size data-size ] [ circular ]
- debug platform packet-trace copy packet { input | output | both } [ size num-bytes ] [ L2 | L3 | L4 ]
- show platform packet-trace { configuration | statistics | summary | packet { all | pkt-num }}
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Cisco IOS XE 3.11S |
In Cisco IOS XE Release 3.11S, this feature was enhanced to include the following features:
- Matched versus traced statistics.
- Trace stop timestamp in addition to trace start timestamp.
The following commands were introduced or modified:
- debug platform packet-trace drop [code drop-num ]
- show platform packet-trace packet {all | pkt-num} [decode]
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Cisco IOS XE Denali 16.3.1 |
In Cisco IOS XE Denali 16.3.1, this feature was enhanced to include Layer3 packet tracing along with IOSd. The following commands were introduced or modified: debug platform packet-trace punt. |