IP Routing Features

Configuring IRDP

Configuring IRDP

The ICMP Router Discovery Protocol (IRDP) is used by ProCurve routing switches to advertise the IP addresses of its router interfaces to directly attached hosts. IRDP is enabled by default. You can enable the feature on a global basis or on an individual VLAN interface basis.

When IRDP is enabled, the routing switch periodically sends Router Adver­ tisement messages out the IP interfaces on which the feature is enabled. The messages advertise the routing switch's IP addresses to directly attached hosts who listen for the messages. In addition, hosts can be configured to query the routing switch for the information by sending Router Solicitation messages.

Some types of hosts use the Router Solicitation messages to discover their default gateway. When IRDP is enabled on the ProCurve routing switch, the routing switch responds to the Router Solicitation messages. Some clients interpret this response to mean that the routing switch is the default gateway. If another router is actually the default gateway for these clients, leave IRDP disabled on the ProCurve routing switch.

IRDP uses the following parameters. If you enable IRDP on individual VLAN interfaces, you can configure these parameters on an individual VLAN inter­ face basis.

■Packet type - The routing switch can send Router Advertisement messages as IP broadcasts or as IP multicasts addressed to IP multicast group 224.0.0.1. The default packet type is IP broadcast.

■Hold time - Each Router Advertisement message contains a hold time value. This value specifies the maximum about of time the host should consider an advertisement to be valid until a newer advertisement arrives. When a new advertisement arrives, the hold time is reset. The hold time is always longer than the maximum advertisement interval. Therefore, if the hold time for an advertisement expires, the host can reasonably conclude that the router interface that sent the advertisement is no longer available. The default hold time is three times the maximum message interval.

■Maximum message interval and minimum message interval - when IRDP is enabled, the routing switch sends the Router Advertisement messages every 450-600 seconds by default. The time within this interval that the routing switch selects is random for each message and is not affected by traffic loads or other network factors. The random interval minimizes the probability that a host will receive Router Advertisement

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