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Tcpdump: Difference between revisions
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* <tt>-n</tt> to disable (per-packet blocking) DNS lookups | * <tt>-n</tt> to disable (per-packet blocking) DNS lookups | ||
* <tt>-s snaplen</tt> to capture more than the default snapshot length. 0 for no limit. | * <tt>-s snaplen</tt> to capture more than the default snapshot length. 0 for no limit. | ||
* <tt>-e</tt> to show link-layer information | |||
==Recipes== | ==Recipes== | ||
* Capture all arp: '''tcpdump arp''' | * Capture all arp: '''tcpdump arp''' | ||
* Capture packets to or from a MAC address M: '''tcpdump | * Capture packets to or from a MAC address M: '''tcpdump ether host M''' | ||
==Gotchas== | |||
* <tt>tcpdump</tt> will not function on a [[DPDK]] interface once a DPDK application has bound the interface | |||
* A filter matching L4 fields (including [[TCP]]/[[UDP]] port) will not match any fragments save the first. Watch for <tt>[+]</tt> to indicate more fragments. | |||
Latest revision as of 07:52, 8 January 2021
Important flags
- -n to disable (per-packet blocking) DNS lookups
- -s snaplen to capture more than the default snapshot length. 0 for no limit.
- -e to show link-layer information
Recipes
- Capture all arp: tcpdump arp
- Capture packets to or from a MAC address M: tcpdump ether host M
