Looking for guidance on network topology changes. Currently our network has 2 different stacks of switches running in layer 2. These switches then connect to a stack of layer 3 switches to do internal routing before hitting our router to the outside world. (See diagram below)

We are looking to implement a Lantronix xPrintServer to print using AirPrint. The problem that we are facing is that we can only see the printers on one side of the building. If we connect the xPrintServer to the East side of the building any iOS devices connected on that side of the building work until you walk to the West side. My thoughts on this are that the layer 3 switch is blocking the traffic from getting to the other stack of switches.

From a network design standpoint is it better to join all layer 2 switches to a single layer 2 switch before connecting to a layer 3 switch? Or would our current setup be the preferred method and we just have it configured incorrectly?

Current Topology: (MDF is on East side of building and IDF is on West side of building) Current Topology


  • VLANS 10-15 are available across all switches.
  • xPrintServer is in VLAN 11 which is where all of the clients that would be using it are located.
  • We currently not attempting to traverse across subnets. We are only wanting to stay on VLAN 11. When we are connected to the IDF(West) side of the building we no longer have AirPrint, but if we are on the MDF(East) side of the building everything works fine.
  • Uplink ports to core switch from MDF and IDF are actually 10G links and they are setup in port channels.
  • Could you provide more detail about where these vlans are present, and in which vlans the xPrintServer and the clients are? From your question, I understand there is no layer 2 link between east and west, but I only see one subnet for each type of devices?
    – Gerben
    Commented Aug 29, 2014 at 20:17
  • From what you have described, you have a single L2 domain across both the East and West sides. Could you provide configurations from devices? If this isn't working, there is probably something configured/misconfigured that is preventing this (bad IGMP snooping config, client isolation, etc).
    – YLearn
    Commented Sep 2, 2014 at 13:21

2 Answers 2


The problem you are experiencing is due to the fact that mDNS (Bonjour/Multicast DNS used by Apples printer discovery protocol) does not traverse across subnets.

There are three possible options I can think of:

  1. To allow your iOS devices on a separate subnet to see the AirPrint printers, you'll need to allow multicast packets to traverse the subnets on the L3 switch. mDNS is a multicast UDP packet to port 5353. There are routers will allow multicast forwarding, this is normally complex configuration and might/might-not be supported by specific Dell switches.

  2. there are specialized print servers available in market which have a way to support AirPrint across networks (requires client side software to be installed). For example - Weprint.

  3. You can have a single VLAN across all the switches to support natural AirPrint. Might not be an ideal network design, but might be most practical in your scenario.

  • The Dell 8132 does support multicast, so option 1 would be good way to go. But I want to question the necessity of 4 gigabit uplinks per switch. That's probably more than you need. Are they bonded together into a single aggregate link? Otherwise, some of the links will not be passing traffic due to spanning tree.
    – Ron Trunk
    Commented Aug 29, 2014 at 21:28

It looks like things are a configuration issue.

After more and more searching I found that the following command was enabled on VLAN 11 on the IDF switch causing things not to function. (Crazy how you can stare at the same problem and not even see it!)

bridge multicast forbidden forward-unregistered

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