Brocade Communications Systems ICX 7250 series, Configuration Manual

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When IRDP is enabled, the Layer 3 switch periodically sends Router Advertisement messages out the IP interfaces on which the feature
is enabled. The messages advertise the Layer 3 switch IP addresses to directly attached hosts who listen for the messages. In addition,
hosts can be configured to query the Layer 3 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 Brocade
Layer 3 switch, the Layer 3 switch responds to the Router Solicitation messages. Some clients interpret this response to mean that the
Layer 3 switch is the default gateway. If another router is actually the default gateway for these clients, leave IRDP disabled on the
Brocade Layer 3 switch.
IRDP parameters
IRDP uses the following parameters. If you enable IRDP on individual ports instead of enabling the feature globally, you can configure
these parameters on an individual port basis:
• Packet type - The Layer 3 switch can send Router Advertisement messages as IP broadcasts or as IP multicasts addressed to
IP multicast group 224.0.0.1. The packet type is IP broadcast.
• Maximum message interval and minimum message interval - When IRDP is enabled, the Layer 3 switch sends the Router
Advertisement messages every 450 - 600 seconds by default. The time within this interval that the Layer 3 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 messages from other routers at the same time. The interval on each
IRDP-enabled Layer 3 switch interface is independent of the interval on other IRDP-enabled interfaces. The default maximum
message interval is 600 seconds. The default minimum message interval is 450 seconds.
• Hold time - Each Router Advertisement message contains a hold time value. This value specifies the maximum amount 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.
• Preference - If a host receives multiple Router Advertisement messages from different routers, the host selects the router that
sent the message with the highest preference as the default gateway. The preference can be a number from 0-4294967296.
The default is 0.
Enabling IRDP globally
To globally enable IRDP, enter the following command.
device(config)# ip irdp
This command enables IRDP on the IP interfaces on all ports. Each port uses the default values for the IRDP parameters. The
parameters are not configurable when IRDP is globally enabled.
Enabling IRDP on an individual port
To enable IRDP on an individual interface and change IRDP parameters, enter commands such as the following.
device(config)# interface ethernet 1/1/3
device(config-if-1/1/3)# ip irdp maxadvertinterval 400
This example shows how to enable IRDP on a specific port and change the maximum advertisement interval for Router Advertisement
messages to 400 seconds.
NOTE
To enable IRDP on individual ports, you must leave the feature globally disabled.
Configuring IP parameters - Layer 3 switches
Brocade FastIron Layer 3 Routing Configuration Guide
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