Not sure how to explain this: I have twenty site that link back to my CO. We are installing an HVAC device at each site. Each HVAC controller sends a UDP broadcast to the other HVAC devices on network so that they see each other. I have a 3Com 5500 layer three switch at each site being used as the router  with a 3Com 4500 switches as the core switch at each site. Some of the controllers are plugged directly into the 5500 and some are plugged into the 4500s. My question is, do I need to enable UDP broadcast on the routers and the switches for this to work properly or should it work regardless?
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Craig BeckCommented:
You need to configure an IP helper address on each router's LAN interface.
You'll need one helper per HVAC device, so at any one site you could have 19 IP helpers configured.

You'd also need to configure the IP forward-protocol command to tell the router to forward broadcasts on the port number the HVAC device uses.

Finally you'll need to enable directed broadcasts.

So, on one site router you might have...

ip directed-broadcast
ip forward-protocol udp <port number>
interface GigabitEthernet0/1
 description LAN INTERFACE
 ip address

ip helper-address       (HVAC at site 2)
ip helper-address      (HVAC at site 3)
ip helper-address       (HVAC at site 4)

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molly22Author Commented:
This works, thanks.
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Networking Protocols

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