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RDP Overview Configuring RDP
page 17-6 OmniSwitch 6600 Family Network Configuration Guide April 2006
RDP Interfaces
An RDP interface is created by enabling RDP on an IP router interface. Once enabled, the RDP interface
becomes active and joins the all-routers IP multicast group (224.0.0.2). The interface then transmits 3
initial router advertisement messages at random intervals that are no greater than 16 seconds apart. This
process occurs upon activation to increase the likelihood that end hosts will quickly discover this router.
After an RDP interface becomes active and transmits its initial advertisements, subsequent advertisements
are transmitted at random intervals that fall between a configurable range of time. This range of time is
defined by specifying a maximum and minimum advertisement interval value. See “Defining the Adver-
tisement Interval” on page 17-9 for more information. Because advertisements are transmitted at random
intervals, the risk of system overload is reduced as advertisements from other routers on the same link are
not likely to transmit at the same time.
It is important to note that advertisements are only transmitted on RDP interfaces if the following condi-
tions are met:
• The RDP global status is enabled on the switch.
• An IP interface exists and is in the enabled state.
• An RDP interface exists and is in the enabled state.
• Either VRRP is disabled or if VRRP is enabled, there is one or more Master IP addresses for the
VLAN. If VRRP is enabled and if there are no Masters IP addresses, router advertisements are not sent
on the VLAN. (See Chapter 19, “Configuring VRRP,” for more information.)
The router advertisement is a multicast packet sent to the all-systems IP multicast group (224.0.0.1) or the
broadcast address. If VRRP is enabled, the message should be filled with IP addresses obtained from
VRRP Master IP address list; otherwise the IP address of the IP router interface is used.
Note that RDP is not recommended for detecting neighboring router failures, referred to as black holes, in
the network. However, it is possible to use RDP as a supplement for black hole detection by setting RDP
interface advertisement interval and lifetime values to values lower than the default values for these
parameters. See “Defining the Advertisement Interval” on page 17-9 and “Setting the Advertisement Life-
time” on page 17-10 for more information.