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problem with IRB on the 6500


i have two sites with the same ip subnet ( and both sites are connected through E1 links on two 6509 (PA-4E1G/120 and when tried to configure IRB for bridging the two sites/subnets i realized that the 6500 does not support the BVI.

i need help on how to configure the two 6500 switches to pass the broadcast through the E1 interfaces as i have a specific appplication that requires the broadcast feature

thanks and regards


Re: problem with IRB on the 6500

to pass a broadcast through a routed interface, you must use the 'ip helper-address x.x.x.x' command.

this command, on the interface of the originating broadcast packet, will tell the router to forward that packet to the ip address specified.

see this link for more info:

Hall of Fame Super Silver

Re: problem with IRB on the 6500


Is it broadcasts from a particular application that you need or is it all broadcasts? If it is broadcasts from a particular application, does the application use UDP or TCP? If you need broadcasts from an application that uses UDP then you can use the combination of ip forward-protocol and ip helper-address to forward broadcasts from a source subnet to a destination subnet.

For an example lets assume that you want broadcasts from an application that uses UDP port 33667 and that the other subnet is You would configure this on the interface where the broadcasts are received:

ip forward-protocol udp 33667

ip helper-address

On the interface to the remote subnet make sure that it includes ip directed-broadcast.