CCNA – Trunking Questions 2
Cisco switches support two trunking protocols 802.1q & ISL. 802.1q is an open standard and is thus compatible between most vendors’ equipment while Inter-Switch Link (ISL) is Cisco proprietary.
The “show interfaces trunk” command and “show interfaces switchport” command can be used to verify the status of an interface (trunking or not). The outputs of these commands are shown below (port Ethernet 1/0 has been configured as trunk):
The “show ip interface brief” command only gives us information about the IP address, the status (up/down) of an interface:
The “show interfaces vlan” command only gives us information about that VLAN, not about which ports are the trunk links: