ICMP Router Discovery Protocol Configuration
IRDP is disabled by default. You can enable the feature on a global basis or on an individual port basis:
- If you enable the feature globally, all ports use the default values for the IRDP parameters.
- If you leave the feature disabled globally but enable it on individual ports, you also can configure the IRDP parameters on an individual port basis.
When IRDP is enabled, the Layer 3 device periodically sends Router Advertisement messages out the IP interfaces on which the feature is enabled. The messages advertise the IP addresses of the device to directly attached hosts who listen for the messages. In addition, hosts can be configured to query the Layer 3 device 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 RUCKUS Layer 3 device, the device responds to the Router Solicitation messages. Some clients interpret this response to mean that the Layer 3 device is the default gateway. If another router is actually the default gateway for these clients, leave IRDP disabled on the RUCKUS Layer 3 device.
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 device 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 device sends the Router Advertisement messages every 450 - 600 seconds by default. The time within this interval that the device 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 device 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.