How can I get broadcast messages to traverse VLANs?
Posted on 2009-05-01
I am administering a small-office network with the following VLANs:
172.16.1.xxx - in-office workstations and servers
172.16.2.xxx - VOIP phones
172.16.3.xxx - VPN VLAN
172.16.5.xxx - WiFi VLAN
Now then. Our office printers are on the first subnet, and so they get IP addresses like 172.16.1.50. Fine.
On Mac OS X (we have several in the office), printers are set-up using mDNS (or Bonjour, as Apple calls it). This setup works fine when a user plugs his laptop to the wired network (also in the 172.16.1/24 subnet), because the mDNS query broadcasts on that subnet, finds the IP address of the printer, and everyone is happy.
When users unplug their laptops from the wired network, they join the WiFi network and are given an IP address in the 172.16.5.xxx network. From there, however, they're unable to print because the mDNS queries are broadcast only to the 172.16.5.xxx subnet, and no printers are connected to that network.
It seems to me that what I need to do is set-up the wireless network to relay broadcast messages to the 172.16.1/24 subnet so that it can find the printers. But I don't think I know how to do that...
Can someone help me figure this out? Specifically, some questions I have that I'm blocking on:
1) Do I need to change the netmask of the wireless network so that broadcasts are sent to the entire 172.16/16 network?
2) I don't want broadcast messages going over the VPN. Will I need to renumber my subnets and then choose a subnet mask 172.16.0.0/x where, 16 < x < 24?
3) Am I on the wrong track with this whole subnet / netmask train of thought? Should I be looking into setting up a custom firewall rule just for this use case?
Thanks in advance,