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I have a device on a VLAN that uses UDP subnet broadcasts to advertise its presence to similar devices.
This works fine on a single VLAN, but now I need to allow it to communicate with similar devices on a second VLAN.
I thought of using the IP helper command in the router, but I am wondering if that only forwards global broadcasts (255.255.255.255)?
My device sends out a subnet broadcast (e.g. 192.168.6.255)
Will IP helper change the destination address to the target subnet (e.g. 192.168.7.255)?
Eamon

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It looks like this varies by implementation. I think you're going to have to test your setup. You can set the ip-helper address to the subnet broadcast address in (at least some) Cisco implementations. If you're developing a solution for resale I'd recommend using the global broadcast address, since you mean that insofar as you want the broadcast to be global. –  Evan Anderson Jun 17 '10 at 12:11

2 Answers 2

got it working, but then hit a broadcast storm as described by Cisco here, http://www.cisco.com/en/US/docs/internetworking/case/studies/cs006.html Convinced customer to stick with one VLAN, so the problem as gone away.
Thanks for the help

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It depends on the specifics of your setup but it could well help yes; have a look HERE to see if it helps.

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I can't tell from that if it only sends global broadcasts or all broadcasts - am I missing something? –  Eamon Jun 17 '10 at 11:15

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