host not pingable through trunk

[suthomas1]

Hello All,

On a trunk port, there are already few vlans allowed. To this, there was another vlan added(vlan 120) and one of the hosts changed its ip to match the new vlan being allowed.

Original trunk port configuration:-
interface port-channel101
  switchport mode trunk
  switchport trunk allowed vlan 20-23
  spanning-tree port type edge
  spanning-tree guard root

new vlan added is 120:-

interface port-channel101
  switchport mode trunk
  switchport trunk allowed vlan 20-23,120
  spanning-tree port type edge
  spanning-tree guard root

After this, we couldn't see the host(which changed ip details to vlan 120) on switch mac table at all & of course it wasn't able to ping the gateway for vlan 120.
The gateway for vlan 120 resides on a firewall which is correctly trunked through.
But we were able to see other vlan 120 mac addresses on the same switch & we were able to ping vla 120 gateway from the switch itself. The final bit was to use some other spare ip's in vlan 120 to verify , but it didn't work.

Appreciate, if folks here can help if there is anything else that can be checked on the switch side or
anything else that might solve this. Thanks in advance.

[dennis.lloyd · Accepted solution]

can you show the interface configuration of the port-channel members on both switches?  Also:

sh int port-chan xxx switchport

sh int port-chan xxx trunk

sh int port-chan xxx status

[suthomas1]

interface Ethernet155/1/10
  switchport mode trunk
  switchport trunk allowed vlan 20-23,120
  channel-group 101


interface Ethernet156/1/10
  switchport mode trunk
  switchport trunk allowed vlan 20-23,120
  channel-group 101

[dennis.lloyd]

so the host that changed it's IP address, that is an access port I assume?  can you show the port config for the port your host is on? and:

sh mac address-table dynamic vlan 120

[suthomas1]

the host is actually a vm host & the trunks above connect to the vm managements.

they are currently using an ip on vlan 20 & it works well. when they change it to vlan 120 thats when the issue is seen.

i checked the mac table during the process of changing/checking, but couldn't see the mac on switches once the ip is changed to vlan 120 from existing vlan 20.

Sorry, the host is now working on vlan 20.

thanks for the reply.

[dennis.lloyd]

no problem.. I got into the habit of clearing the arp cache and mac address-table when moving hosts.  depending on the expiry of the tables, it may cause issues when moving hosts.