How can I get broadcast messages to traverse VLANs?

Posted on 2009-05-01
Last Modified: 2012-06-27

I am administering a small-office network with the following VLANs: - in-office workstations and servers - VOIP phones - VPN VLAN - WiFi VLAN

Now then. Our office printers are on the first subnet, and so they get IP addresses like 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 network. From there, however, they're unable to print because the mDNS queries are broadcast only to the 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 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,
- Anthony
Question by:Tonyboy
    LVL 14

    Accepted Solution

    You are on the wrong track.  One of the significant points of VLAN segmentation is to isolate broadcast traffic within a specific VLAN segment.

    Move the wifi network onto the same VLAN as your servers and computers.   Unless you left out some pertinate information, you are not gaining anything by breaking the WiFi to a seperate VLAN.
    LVL 8

    Expert Comment

    what kind of switch?
    his is pretty common to have to do. Say you have 1 DHCP server but multiple VLAN's you will need to do the same thing.

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