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Overwrite buffer from beginning when full, default is non-circularĮtherType is a two-octet field in an Ethernet frame. Just a note of caution – applying captures will add to memory utilization so keep an eye on memory before enabling captures with max buffer The traffic can be analyed into the router itself, even if it’s uneasy: #show monitor capture buffer BUFFER dumpġ4:56:56.370 CEST : IPv4 LES CEF : Fa0/0 NoneĨ4387970: F3AC9CAF CA700F25 08004500 05DC5ABB s./Jp.%.E.These are the options available access-listĬapture packets that match access-list, when you specify access-list make sure that you specify the traffic in both direction if you want to capture bi-directional trafficĭefault is 512 KB and you can configure it upto 32 MB, you do not need to change this in most cases. General Parameters TLV (0x0001), length: 12

Monitor capture point associate CAPTURE BUFFERįinally the capture must be started and stopped when not needed anymore: monitor capture point start CAPTUREĪt this point the buffer can be exported to an external system: monitor capture buffer BUFFER export The next step requires to define which interfaces must be monitoed and where store data: monitor capture point ip cef CAPTURE FastEthernet0/0 both Monitor capture buffer BUFFER filter access-list Monitored-Host Permit ip 10.0.0.0 0.0.0.255 host 10.1.1.1Ī buffer must be defined and bounded to the previos defined ACL: monitor capture buffer BUFFER size 512 max-size 256 circular Data within the buffer can be exported and analyzed using external tools, like tcpdump or Wireshark.Īn ACL must be defined to match interesting traffic only: ip access-list extended Monitored-Host The configuration requires a specific buffer where packets will be stored.

Embedded Packet Capture, available from IOS 12.4T, can capture packet in tcpdump format.