C H A P T E R 11 Configuring Vlan Trunks On Fast Ethernet And Gigabit Ethernet Ports - Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual

Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports
Table 11-2 Fast Ethernet and Gigabit Ethernet Trunk Encapsulation Type
Encapsulation Function
dot1q Specifies 802.1Q encapsulation on the trunk link. 802.1Q trunks are supported in Catalyst 4000 family
with 802.1Q-capable hardware. Automatic negotiation of 802.1Q trunks is supported in software
release 4.2 and later.
The trunking mode, the trunk encapsulation type, and the hardware capabilities of the two connected
ports determine whether a trunk link comes up and the type of trunk the link becomes.
the result of the possible trunking configurations.
Table 11-3 Results of Possible Fast Ethernet and Gigabit Ethernet Trunk Configurations
Neighbor Port
Trunk Mode and
Trunk
Encapsulation
off
dot1q
on
dot1q
desirable
dot1q
auto
dot1q
DTP is a point-to-point protocol. However, some internetworking devices might forward DTP frames
Note
improperly. To avoid this problem, ensure that trunking is turned off on ports connected to non-switch
devices if you do not intend to trunk across those links. When manually enabling trunking on a link to a
Cisco router, use the nonegotiate keyword to cause the port to become a trunk but not generate DTP
frames.
78-12647-02
Local Port Trunk Mode and Trunk Encapsulation
off
dot1q
Local:
Nontrunk
Neighbor:
Nontrunk
Local:
Nontrunk
Neighbor:
1Q trunk
Local:
Nontrunk
Neighbor:
Nontrunk
Local:
Nontrunk
Neighbor:
Nontrunk
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
on desirable
dot1q dot1q
Local: Local:
1Q trunk Nontrunk
Neighbor: Neighbor:
Nontrunk Nontrunk
Local: Local:
1Q trunk 1Q trunk
Neighbor: Neighbor:
1Q trunk 1Q trunk
Local: Local:
1Q trunk 1Q trunk
Neighbor: Neighbor:
1Q trunk 1Q trunk
Local: Local:
1Q trunk 1Q trunk
Neighbor: Neighbor:
1Q trunk 1Q trunk
Understanding How VLAN Trunks Work
Table 11-3
auto
dot1q
Local:
Nontrunk
Neighbor:
Nontrunk
Local:
1Q trunk
Neighbor:
1Q trunk
Local:
1Q trunk
Neighbor:
1Q trunk
Local:
Nontrunk
Neighbor:
Nontrunk
shows
11-3