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Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter38 Configuring IP Unicast Routing
Configuring IP Addressing
If you change the maxadvertinterval value, the holdtime and minadvertinterval values also change,
so it is important to first change the maxadvertinterval value, before manually changing either the
holdtime or minadvertinterval values.
Use the no ip irdp interface configuration command to disable IRDP routing.
Configuring Broadcast Packet Handling
After configuring an IP interface address, you can enable routing and configure one or more routing
protocols, or you can configure the way the switch responds to network broadcasts. A broadcast is a data
packet destined for all hosts on a physical network. The switch supports two kinds of broadcasting:
•A directed broadcast packet is sent to a specific network or series of networks. A directed broadcast
address includes the network or subnet fields.
•A flooded broadcast packet is sent to every network.
Note You can also limit broadcast, unicast, and multicast traffic on Layer 2 interfaces by using the
storm-control interface configuration command to set traffic suppression levels. For more information,
see Chapter 25, “Configuring Port-Based Traffic Control.”
Routers provide some protection from broadcast storms by limiting their extent to the local cable.
Bridges (including intelligent bridges), because they are Layer 2 devices, forward broadcasts to all
network segments, thus propagating broadcast storms. The best solution to the broadcast storm problem
is to use a single broadcast address scheme on a network. In most modern IP implementations, you can
set the address to be used as the broadcast address. Many implementations, including the one in the
switch, support several addressing schemes for forwarding broadcast messages.
Perform the tasks in these sections to enable these schemes:
•Enabling Directed Broadcast-to-Physical Broadcast Translation, page38-15
•Forwarding UDP Broadcast Packets and Protocols, page38-16
•Establishing an IP Broadcast Address, page38-16
•Flooding IP Broadcasts, page 38-17
Step6 ip irdp maxadvertinterval seconds (Optional) Set the IRDP maximum interval between advertisements. The
default is 600 seconds.
Step7 ip irdp minadvertinterval seconds (Optional) Set the IRDP minimum interval between advertisements. The
default is 0.75 times the maxadvertinterval. If you change the
maxadvertinterval, this value changes to the new default (0.75 of
maxadvertinterval).
Step8 ip irdp preference number (Optional) Set a device IRDP preference level. The allowed range is –231
to 231. The default is 0. A higher value increases the router preference
level.
Step9 ip irdp address address [number] (Optional) Specify an IRDP address and preference to proxy-advertise.
Step10 end Return to privileged EXEC mode.
Step11 show ip irdp Verify settings by displaying IRDP values.
Step12 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose