Configure Packet Truncation

Follow this procedure to truncate a packet to conform to the length required by your analysis tools.

About this task

You configure packet truncation in a listener policy. You can include other settings in addition to packet truncation. Minimum truncated packet length is 64 bytes.

Procedure

  1. Enter the Config mode.
    The command line changes to configuration mode.
    device(config)# 
  2. Configure an ACL of type IPv4, IPv6, or MAC and any actions.
    device(config)# ip access-list acl3-ipv4
    device(config-ip-acl)# seq 12 permit ip any any count
    The specified ACL and configured actions are bound to a listener policy.
  3. Create the listener policy, including the truncate subcommand with any other action subcommands for the policy.
    Note

    Note

    A listener policy supports only one of each of each ACL type: IPv4, IPv6, MAC.
    device(config)# listener-policy lp-3 18
    device(config-listener-policy)# match ip access-list acl3-ipv4
    device(config-listener-policy)# truncate 512
    device(config-listener-policy)# description "truncate ip packets lp"
  4. Configure an egress policy and bind the listener policy, specifying any additional egress actions.
    Note

    Note

    An egress can be associated with only one listener policy.
    device(config)# egress e3
    device(config-egress)# set listener-policy lp-3 18
    device(config-egress)# description DirectTool
    device(config-egress)# precedence 1 interface ethernet 2/14
  5. Configure an egress group and associate it with the egress policy.
    device(config)# egress-group eg_5 
    device(config-egress-group)# description e-group_5
    device(config-egress-group)# set egress e3
  6. Configure the route map and set any other parameters, such as forwarding actions, match ip access list, and the egress-group.
    Note

    Note

    A route-map policy supports only one match-ACL per layer.
    device(config)# route-map R2 10 
    device(config-route-map)# match ip access-list acl3-ipv4
    device(config-route-map)# set egress-group eg_5
    device(config-route-map)# forward-action permit
  7. Configure an ingress group and associate a route map.
    Note

    Note

    An ingress group can be associated with only one route map.
    device(config)# ingress-group TAP_TRAFFIC
    device(config-ingress-group)# set route-map R2
  8. Configure the interface port and channel for ingress traffic.
    Note

    Note

    In the following example, traffic is coming in on slot/port-number 2/3.
    interface ethernet 2/3
    description From_TAP
    set ingress-group TAP_TRAFFIC
    no shutdown
  9. Configure the interface port and channel for egress traffic.
    Note

    Note

    In the following example, traffic is leaving on slot/port-number 2/14.
    interface ethernet 2/14
    speed 40000
    description To_Tool
    no shutdown