Enabling forwarding of directed broadcasts

A directed broadcast is an IP broadcast to all devices within a single directly-attached network or subnet. A net-directed broadcast goes to all devices on a given network. A subnet-directed broadcast goes to all devices within a given subnet.

NOTE

A less common type, the all-subnets broadcast, goes to all directly-attached subnets. Forwarding for this broadcast type also is supported, but most networks use IP multicasting instead of all-subnet broadcasting.

Forwarding for all types of IP directed broadcasts is disabled by default. You can enable forwarding for all types if needed. You cannot enable forwarding for specific broadcast types.

To enable forwarding of IP directed broadcasts, enter the ip directed-broadcast command in device configuration mode.

device # configure terminal
device(config)# ip directed-broadcast

Syntax: [no] ip directed-broadcast

Brocade software makes the forwarding decision based on the router's knowledge of the destination network prefix. Routers cannot determine that a message is unicast or directed broadcast apart from the destination network prefix. The decision to forward or not forward the message is by definition only possible in the last hop router.

To disable the directed broadcasts, enter the no ip directed-broadcast command in device configuration mode.

device # configure terminal
device(config)# no ip directed-broadcast

To enable directed broadcasts on an individual interface instead of globally for all interfaces, enter the ip directed-broadcast command at the interface configuration level as shown in the following example.

device # configure terminal
device(config)# interface ethernet 1/1/1
device(config-if-1/1/1 # ip directed-broadcast

Contents

Enabling forwarding of directed broadcasts