Recently one of our vendor added couple of new Cisco Catalyst 4506 Series distribution switches to our network for their PACS project. Those two newly added Cisco 4506 Series distribution switches are connected to our Core Cisco Catalyst 6513Series Switches using a layer 23 uplink ( as a trunk port). For VLAN redundancy we are using HSRP protocol. The newly added Cisco 4506 Series distribution switches are configured in VTP Client mode, we could see the VTP status was updated and all the VLAN were created. But there was a problem; there was not communication between any of the VLANS in the new Cisco 4506 Series distribution switches, after trouble shooting we figured out “ip routing” was enabled. When we disabled the ip routing with “no ip routing” command everything started working.