Switchport Trunk - Cisco Catalyst 3750 Metro Command Reference Manual

switchport trunk

•
•
•
Defaults The default encapsulation is negotiate.
VLAN 1 is the default native VLAN ID on the port.
The default for all VLAN lists is to include all VLANs.
The default ethertype value for 802.1Q encapsulation is 0x8100.
Command Modes
Interface configuration
Command History Release
12.1(14)AX
Usage Guidelines
Encapsulation:
•
•
•
Catalyst 3750 Metro Switch Command Reference
2-726
You can add extended-range VLANs to the allowed VLAN list, but not to the
Note
pruning-eligible VLAN list.
Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.
remove removes the defined list of VLANs from those currently set instead of replacing the list.
Valid IDs are from 1 to 1005; extended-range VLAN IDs are valid in some cases.
You can remove extended-range VLANs from the allowed VLAN list, but you cannot
Note
remove them from the pruning-eligible list.
Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.
except lists the VLANs that should be calculated by inverting the defined list of VLANs. (VLANs
are added except the ones specified.) Valid IDs are from 1 to 1005. Separate nonconsecutive VLAN
IDs with a comma; use a hyphen to designate a range of IDs.
vlan-atom is either a single VLAN number from 1 to 4094 or a continuous range of VLANs
described by two VLAN numbers, the lesser one first, separated by a hyphen.
Modification
This command was introduced.
The switchport trunk encapsulation command is supported only on platforms and interface
hardware that can support both ISL and 802.1Q formats.
In Cisco IOS Release 12.2(25)EY and later, ISL encapsulation is supported only on standard ports
and not on ES ports. ES ports support only 802.1Q encapsulation. When you upgrade a switch from
Cisco IOS Release 12.2(14)AX to Cisco IOS Release 12.2(25)EY or later, during the initial
configuration process the switchport trunk encapsulation option is rejected on ES ports and an error
message is issued. You can ignore this error message. If you save the new configuration and later
re-install the 12.1(14)AX image, the trunk encapsulation method originally configured on the ES
ports is lost and the ES ports use the default encapsulation method, which is to negotiate.
You cannot configure one end of the trunk as an 802.1Q trunk and the other end as an ISL or
nontrunk port. However, you can configure one port as an ISL trunk and a different port on the same
switch as an 802.1Q trunk.
Chapter 2 Catalyst 3750 Metro Switch Cisco IOS Commands
OL-9645-10