Two eth-trunk sub-interface directly connected but can't ping each other

Hi, everyone! Today I’m going to introduce two eth-trunk sub-interface directly connected but can't ping each other cases.

The topology is this : S6700(eth-trunk100.100)----S6700(eth-trunk100.100).

The configuration of interface is below:

SW1:

interface Eth-Trunk100 

undo portswitch

#

interface Eth-Trunk100.100

 dot1q termination vid 100

 ip address 172.16.0.1 255.255.255.252

SW2:

interface Eth-Trunk100

 undo portswitch

#

interface Eth-Trunk100.100

 dot1q termination vid 100

 ip address 172.16.0.2 255.255.255.252

The issue is that ping from SW1 to SW2 is not reachable.

checking the ARP table and found that can't learning peer arp information;

Solution is that: add the arp broadcast enable command on the sub-interface eth-trunk.

interface Eth-Trunk100.100  arp broadcast enable

The reason is that: VLAN tag termination sub-interfaces discard broadcast packets after receiving the packets. To permit a VLAN tag termination sub-interface to forward broadcast packets, run the arp broadcast enable command on the sub-interface to enable ARP broadcast.

You are welcome to ask me any questions!