Fnode Networks » helper-address http://www.fnode.com A Network Systems & Technology Blog Mon, 16 Aug 2010 11:27:55 +0000 en hourly 1 http://wordpress.org/?v=abc IP helper-address Explained http://www.fnode.com/2009/08/ip-helper-address-explained/ http://www.fnode.com/2009/08/ip-helper-address-explained/#comments Tue, 18 Aug 2009 14:58:35 +0000 Nish Vamadevan http://www.fnode.com/?p=441

All broadcasts messages are dropped by the router when it receives on an interface. This specific command is enables the router to convert the broadcast messages distended for a specific destination into unicast. This interface level command needs to be applied on the interface which the broadcast receives from.

R1(config-if)#ip helper-address 10.10.10.10

Also there are other options where you point the address to a vrf etc…

The following broadcasts are forwarded by default…

TIME – Port 37
TACACS – Port 49
DNS – Port 53
BOOTP/DHCP Server – Port 67
BOOTP/DHCP Client – Port 68
TFTP – Port 69
NetBIOS Name Service – Port 137
NetBios Datagram Service – Port 138

Other protocols can be forwarded by using the following Global config commanding…

R1(config)#ip forward-protocol udp ?

Use the ? to see the supported protocols. You may use the following command to remove a specific protocol being forwarded…

R1(config)#no ip forward-protocol udp ?

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