Friday, May 25, 2012

The Case of the Missing Switches

One of my clients had me setup a new Cisco network side by side with their existing HP ProCurve network last fall.  The two networks are linked by a gigabit Ethernet link and the Cisco core (4507R+E) is serving as the default gateway for all of the VLANs on the Cisco side and the one legacy VLAN on the HP ProCurve side.  Everything is working fine for normal network clients on the various VLANs.

Recently, the network administrator at the client site got time to connect to the switches to learn more about the config.  In doing so he discovered that the access layer switches (2960S) were not accessible from any device not on the same management VLAN as their management IPs.  The core switch which is on the same VLAN is accessible from any other VLAN.  Right now the only way to contact the access switches is to ssh from the core or to place a workstation on the management VLAN.

So far I have ruled out/checked out the following:

  • Duplicate IPs
  • Network Loops
  • The management VLAN is trunked properly across the 10Gbps uplinks to the access switches.
  • The management VLAN is in the core's routing table.
  • The access switches are listed in both the mac address table and the ARP table of the core switch.
  • The SVI for the management VLAN is UP/UP

I'm looking for ideas of where else to check for the cause of this behavior.  Thanks in advance for any help and I promise to post the solution when it comes.


  1. Is ip default-gateway x.x.x.x set on the switch? It should be on the same segment as your management SVI.

    If you have routing enabled with ip routing, you will need to define a default static

  2. Thank you Eric! It was the ip default-gateway command. We had it configured to the old HP network gateway during configuration for remote access and forgot to move it to the Cisco network gateway.