Feature Interactions
Trunkinginteracts with other features in these ways:
•Atrunk port cannot be a secure port.
•Atrunk port cannot be a tunnel port.
•Trunkports can be grouped into EtherChannel port groups, but all trunks in the group must have the
sameconfiguration. When a group is first created, all ports follow the parameters set for the first port
tobe added to the group. If you change the configuration of one of these parameters, the switch propagates
thesetting that you entered to allports in thegroup:
◦Allowed-VLANlist.
◦STPport priorityfor each VLAN.
◦STPPort Fast setting.
◦Trunkstatus:
Ifone port in a port group ceasesto be a trunk, all ports cease to be trunks.
•Werecommend that you configure no more than 24 trunk ports in Per VLAN Spanning Tree (PVST)
modeand no more than 40 trunk ports in Multiple Spanning Tree (MST) mode.
•Ifyou try to enable IEEE 802.1x on a trunk port, an error message appears, and IEEE 802.1x is not
enabled.If you try to changethe mode of an IEEE802.1x-enabled port to trunk, theport mode is not
changed.
•Aport in dynamic mode can negotiate with its neighbor to become a trunk port. If you try to enable
IEEE802.1x on a dynamic port, an error message appears, and IEEE 802.1x is not enabled. If you try
tochange the mode of an IEEE802.1x-enabled port to dynamic, the port mode is not changed.
Related Topics
Configuringa Trunk Port, on page 67
Example:Configuring an IEEE802.1Q Trunk, on page 80
Default Layer 2 Ethernet Interface VLAN Configuration
Thefollowing tableshows the defaultLayer 2 Ethernetinterface VLAN configuration.
Table 11: Default Layer 2 Ethernet Interface VLAN Configuration
Default SettingFeature
switchportmode dynamic autoInterfacemode
switchporttrunk encapsulation negotiateTrunkencapsulation
VLANs1 to4094AllowedVLAN range
Catalyst 2960-XR Switch VLAN Configuration Guide, Cisco IOS Release 15.0(2)EX1
66 OL-29440-01
Configuring VLAN Trunks
Feature Interactions