3430 Interface 802.1q mode and LLDP

[ctsjgregory]

Hello,

I have noticed recently that when I put an interface into 802.1q mode with a native VLAN 1 sub-interface and any number of other VLAN sub-interfaces, that LLDP no longer works.

If I put the interface back in standard IP Routing mode, LLDP works again.

Am I missing something in my config or is this just simply not supported?

Thanks,

Jordan

[petetransitguy]

I think what you mean by "standard IP Routing mode," is this configuration:

Router:

interface <link to switch>

speed 100

full-duplex

encapsulation dot1q

no shutdown

Switch:

interface <uplink to router>

speed 100

full-duplex

switchport mode trunk

no shutdown

interface vlan 1

no ip address

shutdown

interface vlan <not VLAN 1>

ip address 192.168.0.1 255.255.255.0

no shutdown

If no other vlan is designated as native, VLAN 1 becomes the native VLAN by default. It should still send lldp even if it's shut down.

My guess is that you want to do subinterfaces to restrict traffic from the switch to the router. If you have a bigger goal than just seeing lldp, please post that along with a partial configuration from the router interface and the switch (uplinks, VLANs, anything else useful).

[Anonymous · Accepted solution]

-  LLDP is not supported on Ethernet interfaces with 802.1q encapsulation enabled. Please do not hesitate to let us know if you have any questions.

Thanks,

Noor