switch and UDP

[ferix]

Hmm...
I guess you're confusing UDP with multicasting/broadcasting.
UDP works well with swithes in unicasting (just one target machine or IP address) and even multicasting/broadcasting.
Multicasting and broadcasting "should" work on switches, if they are enabled to do so. Some switches discard multitarget packets by default, if they are not ARP or RARP packets, of course.
Note that this behaviour only occurs on "smart" switches that can be managed.
Routers will discard broadcast packets.

[ferix]

We've got some applications running that use UDP for (directed) broadcasting and it works fine with all our switches, from 12 years old to brand new, managed or not (the managed ones are able to filter on demand though). Even got it to work over routed VPN, but that's a long story...
Multicast I haven't worked with, but it should also work with any decent switch.
Unicast TCP or UDP will always work through any switch or router (unless filtered).

Note that some managed switches, as Cabletron or Enterasys, discard non ARP broadcasting packets by default... At least, the models we've got at my job.