The ICMP Router Discovery Protocol (IRDP) is used by HP routing switches to advertise the IP addresses of their router interfaces to directly attached hosts. IRDP is disabled 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 Advertisement 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 HP 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 HP routing switch.
IRDP uses the following parameters. If you enable IRDP on individual VLAN interfaces, you can configure these parameters on an individual VLAN interface 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 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. |
| 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 messages from other routers at the same time. The interval on each IRDP-enabled routing 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. |
| Preference | If a host receives multiple Router Advertisement messages from different routers, the host selects the router that send the message with the highest preference as the default gateway. The preference can be a number from -4294967296 to 4294967295. The default is 0. |
This command enables IRDP on the IP interfaces on all ports. Each port uses the default values for the IRDP parameters.
To enable IRDP on an individual VLAN interface and configure IRDP parameters, enter commands such as the following:
This example shows how to enable IRDP on a specific interface (VLAN 1) and change the maximum advertisement interval for Router Advertisement messages to 400 seconds.
Syntax:
[no]
ip irdp[ broadcast | multicast ] [holdtime <seconds>] [maxadvertinterval <seconds>] [minadvertinterval <seconds>] [preference <number>]
[broadcast | multicast]Specifies the packet type the routing switch uses to send the Router Advertisement:
broadcastThe routing switch sends Router Advertisements as IP broadcasts.
multicastThe routing switch sends Router Advertisements as multicast packets addressed to IP multicast group 224.0.0.1. This is the default.
holdtime <seconds>Specifies how long a host that receives a Router Advertisement from the routing switch should consider the advertisement to be valid.
When a host receives a new Router Advertisement message from the routing switch, the host resets the hold time for the routing switch to the hold time specified in the new advertisement. If the hold time of an advertisement expires, the host discards the advertisement, concluding that the router interface that sent the advertisement is no longer available. The value must be greater than the value of the maxadvertinterval parameter and cannot be greater than 9000.
The default is three times the value of the maxadvertinterval parameter.
maxadvertintervalSpecifies the maximum amount of time the routing switch waits between sending Router Advertisements. You can specify a value from 1 to the current value of the holdtime parameter.
The default is 600 seconds.
minadvertintervalSpecifies the minimum amount of time the routing switch can wait between sending Router Advertisements. The default is three-fourths (0.75) the value of the maxadvertinterval parameter.
If you change the maxadvertinterval parameter, the software automatically adjusts the minadvertinterval parameter to be three-fourths the new value of the maxadvertinterval parameter. If you want to override the automatically configured value, you can specify an interval from 1 to the current value of the maxadvertinterval parameter.
preference <number>Specifies the IRDP preference level of this routing switch. If a host receives Router Advertisements from multiple routers, the host selects the router interface that sent the message with the highest preference as the host's default gateway.
The valid range is -4294967296 to 4294967295.
The default is 0.
To display IRDP information, enter show ip irdp from any CLI level.
Output for show ip irdp
HP Switch# show ip irdp
Status and Counters - ICMP Router Discovery Protocol
Global Status : Disabled
VLAN Name Status Advertising Min int Max int Holdtime Preference
Address (sec) (sec) (sec)
------------- -------- ----------- ------- ------- -------- ----------
DEFAULT_VLAN Enabled multicast 450 600 1800 0
VLAN20 Enabled multicast 450 600 1800 0
VLAN30 Enabled multicast 450 600 1800 0