Trunks on old Cisco switches

When dealing with older Cisco switches it is worth remembering that ISL was once the default trunking protocol on these devices. You can check the trunking protocol used on a given interface using the show interface [interface_name] switchport command. To force a specific protocol, use the switchport trunk encapsulation [dot1q|isl] interface configuration mode command. I’ve come across this problem while trying to setup a trunk between Cisco WS-C3524-XL and HP 1700-24 switches (the latter uses 802.1q by default).


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