Forwarding Broadcasts

[monkp]

How do I forward broadcasts from one network to another network?

[mainesy]

Use the ip directed-broadcast command on the interfaces you wish to allow broadcast forwarding.

Example:

router(config)# int fa 0/1

router(config-inf)# ip directed-broadcast

router(config-inf)# exit

Hope this helps.

Josh

[bena]

Just be careful as to where you forward the broadcasts.

Carefully think about the impact of forwarding them.

[lgijssel]

To forward UDP broadcast traffic to a node on anther network, use ip helper.

router(config)# int fa 0/1

router(config-inf)# ip helper-address x.x.x.x

Use this command on the interface from which you expect the broadcast to arrive. ip helper-adress will forward a range of "standard protocols". To limit this somewhat, you can specify what you want to block:

conf t

no ip forward-protocol udp tftp

no ip forward-protocol udp nameserver

no ip forward-protocol udp domain

no ip forward-protocol udp time

no ip forward-protocol udp netbios-ns

no ip forward-protocol udp netbios-dgm

no ip forward-protocol udp tacacs

Use the question mark to see all options.

no ip forward-protocol ?

We are using this mechanism to forward DHCP to a central server. Works fine.

Regards,

Leo