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==========
icp.config
==========

.. configfile:: icp.config

The :file:`icp.config` file defines ICP peers (parent and sibling caches).

.. important::

    After you modify the icp.config file, navigate to the
    Traffic Server bin directory and run the :option:`traffic_line -x` command to
    apply the changes. When you apply the changes to a node in a cluster,
    Traffic Server automatically applies the changes to all other nodes in
    the cluster.

Format
======

Each line in the icp.config file contains the name and configuration
information for a single ICP peer in the following format::

    host : host_IP : peer_type : proxy_port : icp_port : MC_on : MC_IP : MC_TTL :

Each field is described in the following list.

*``host``* {#host}
    The hostname of the ICP peer.

    This field is optional; if you do not specify the hostname of the
    ICP peer, you must specify the IP address.

*``host_IP``* {#host_IP}
    The IP address of the ICP peer.

    This field is optional; if you do not specify the IP address of the
    ICP peer, you must specify the hostname.

*``ctype``* {#ctype}
    Use the following options:

    -  1 to indicate an ICP parent cache
    -  2 to indicate an ICP sibling cache

*``proxy_port``* {#proxy_port}
    The port number of the TCP port used by the ICP peer for proxy
    communication.

*``icp_port``* {#icp_port}
    The port number of the UDP port used by the ICP peer for ICP
    communication.

*``MC_on``* {#mc_on}
    Enable or disable MultiCast:

    -  0 if multicast is disabled
    -  1 if multicast is enabled

*``MC_ip``* {#mc_ip}
    The MultiCast IP address.

*``MC_ttl``* {#mc_ttl}
    The multicast time to live. Use the following options:

    -  1 if IP multicast datagrams will not be forwarded beyond a single
       subnetwork
    -  2 to allow delivery of IP multicast datagrams to more than one
       subnet (if there are one or more multicast routers attached to
       the first hop subnet).

Examples
========

The following example configuration is for three nodes: the local host,
one parent, and one sibling.

::

    localhost:0.0.0.0:3:8080:3130:0:0.0.0.0:1
    host1:123.12.1.23:1:8080:3131:0:0.0.0.0:1
    host2:123.12.1.24:2:8080:3131:0:0.0.0.0:1