System information

Configuring Interfaces and TCP/IP Features
5-17
To avoid broadcast storms, use a single broadcast address scheme on a network and
set the address to be used as the broadcast address. The BSR can accept and interpret
all possible forms of broadcast addresses.
Defining Broadcast Address
You can use several IP commands to perform broadcast tasks.
1. To define a broadcast address for an interface, use the ip broadcast-address
command in Interface Configuration mode. You specify an IP address to set the
broadcast address, as shown in the example below:
MOT(config-if)#ip broadcast-address <A.B.C.D>
where:
A.B.C.D is the interface IP address.
Use the no ip broadcast-address command to restore the default IP broadcast
address for an interface.
2. To enable broadcasting of all directed broadcasts to all addresses in the host
portion of an IP address, use the ip directed-broadcast command in Interface
Configuration mode, as shown in the example below:
MOT(config-if)#ip directed-broadcast
Use the no ip directed-broadcast command to disable broadcasting to all
addresses.
Configuring the MTU
Fragmentation occurs when an IP datagram is too large for a network maximum
transmission unit (MTU) size, and the large datagram is divided into several smaller
pieces for transmission. Lower layer protocols may also set the MTU. If the MTU
that is set in lower layers differs from the MTU that is set at the IP layer, the BSR uses
the lower value.
To set the MTU for packets on an interface, use the ip mtu command in Interface
Configuration mode. On some interfaces, such as cable, you cannot set the MTU.
MOT(config-if)#ip mtu <size>