Network Topology Suggestions for Optimal Performance

layer2layer3routingswitch

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

Update:

  • 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.

Best Answer

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.

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