Configuring UDP broadcast forwarding on individual VLANs

This command routes an inbound UDP broadcast packet received from a client on the VLAN to the unicast or broadcast address configured for the UDP port type.

Syntax: 


no ip forward-protocol udp ip-address [port-number | port-name]

Used in a VLAN context to configure or remove a server or broadcast address and its associated UDP port number. You can configure a maximum of 16 forward-protocol udp assignments in a given VLAN. The switch allows a total of 256 forward-protocol udp assignments across all VLANs.

You can configure UDP broadcast forwarding addresses regardless of whether UDP broadcast forwarding is globally enabled on the switch. However, the feature does not operate unless globally enabled.

ip-address
This can be either of the following:

  • The unicast address of a destination server on another subnet. For example: 15.75.10.43.

  • The broadcast address of the subnet on which a destination server operates. For example, the following address directs broadcasts to All hosts in the 15.75.11.0 subnet: 15.75.11.255.

NOTE:

The subnet mask for a forwarded UDP packet is the same as the subnet mask for the VLAN (or subnet on a multinetted VLAN) on which the UDP broadcast packet was received from a client.

udp-port-#

Any UDP port number corresponding to a UDP application supported on a device at the specified unicast address or in the subnet at the specified broadcast address. For more information on UDP port numbers, refer to TCP/UDP port number ranges.

port-name
Allows use of common names for certain well-known UDP port numbers. You can type in the specific name instead of having to recall the corresponding number:
dns

Domain name service (53)

ntp

Network time protocol (123)

netbios-ns

NetBIOS name service (137)

netbios-dgm

NetBIOS datagram service (138)

radius

Remote authentication dial-in user service (1812)

radius-old

Remote authentication dial-in user service (1645)

rip

Routing information protocol (520)

snmp

Simple network management protocol (161)

snmp-trap

Simple network management protocol (162)

tftp

Trivial file transfer protocol (69)

timep

Time protocol (37)

Example

The following command configures the routing switch to forward UDP broadcasts from a client on VLAN 1 for a time protocol server: 

switch(vlan-1)# ip forward-protocol udp 15.75.11.155 timep