UDP Broadcasts across subnets

[kalmanTRF]

We have an in-house written application that would like to use udp broadcasts to all PCs ( about 1500 )using this application across subnets. We have several subnets and one or 2 machines will do the actual sending out of messages. These broadcast messages will not be used that frequently.

Basically, I am wondering what is the most efficient way I could get these broadcasts from this one node to all other nodes in every subnet, with out affecting traffic loads? I have seen directed broadcasts with ACL and several using IP helper addresses. I am leaning towards the directed broadcasts. Since this is a function that that won't be used very much I am unsure of what method to use.

Anyone with suggestions or experience with this would be greatly appreciated?

 

[BuckWeet]

I think really you need to look at a multicast solution..

To my knowledge directed broadcasts and using the ip helper will only go to one remote machine on the far subnet, not many machines..

anyone else comment on this??

BuckWeet

 

[pmesjar]

If you want to use helper addressing, you must permit directed broadcast on every interface UDP broadcast will be sent on via:

Router(config-if)# ip directed-broadcast

as they are denied by default. Then set up ip helper-address using broadcast address to these subnets, and use command "ip forward-protocol udp <port>" to forward your application port to destinations requiring it. Last two commands should be set up on router interfaces where your 2 machines are connected.

Be aware that enabling directed broadcasts can help in some sort of DoS attacks, which exploit this feature when enabled (eg. smurf attack). Properly set up ACLs should be configured.

Multicast solution might be more efficient depending on whether all hosts need to get your UDP broadcasts or not. If yes, then there is no point to enabling multicast.

Peter Mesjar
CCNA, A+ certified
pmesjar@centrum.sk