Cisco WS-C4003 Software Guide - Page 179
Encapsulation, Function, Neighbor Port, Trunk Mode and, Trunk
View all Cisco WS-C4003 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 179 highlights
Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports Understanding How VLAN Trunks Work Table 11-2 Fast Ethernet and Gigabit Ethernet Trunk Encapsulation Type Encapsulation dot1q Function 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. Table 11-3 shows 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 Local Port Trunk Mode and Trunk Encapsulation off dot1q on dot1q desirable dot1q off dot1q Local: Nontrunk Local: 1Q trunk Local: Nontrunk Neighbor: Nontrunk Neighbor: Nontrunk Neighbor: Nontrunk on dot1q Local: Nontrunk Local: 1Q trunk Local: 1Q trunk Neighbor: 1Q trunk Neighbor: 1Q trunk Neighbor: 1Q trunk desirable dot1q Local: Nontrunk Local: 1Q trunk Local: 1Q trunk Neighbor: Nontrunk Neighbor: 1Q trunk Neighbor: 1Q trunk auto dot1q Local: Nontrunk Local: 1Q trunk Local: 1Q trunk Neighbor: Nontrunk Neighbor: 1Q trunk Neighbor: 1Q trunk auto dot1q Local: Nontrunk Neighbor: Nontrunk Local: 1Q trunk Neighbor: 1Q trunk Local: 1Q trunk Neighbor: 1Q trunk Local: Nontrunk Neighbor: Nontrunk Note DTP is a point-to-point protocol. However, some internetworking devices might forward DTP frames 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 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 11-3