ccna what you need to know

ccna what you need to know.If the trunk mode is set to no-negotiate, the interface will be trunk-connected and automatically tag frames using VLAN information, but no DTP messages will be generated because DTP is disabled. This mode is typically used when connecting to a non-Cisco device because non-Cisco devices do not understand DTP, a Cisco-specific trunking protocol, and cannot understand DTP messages.If trunk mode is set to off,the interface will be an access link. In this mode, no DTP messages will be generated and no frames will be marked.Table 12.5 indicates when a trunk connection will be established between switches: one end is configured as on or desirable, and the other end is configured as on, desirable, or auto; or both ends are configured as no-negotiateo Note that with mode no-negotiate, a trunk connection will be established, but DTP will not be used, and when using mode on, desirable, or auto, DTP will be used O One advantage of using mode on, desirable, or auto is that DTP will check the trunk characteristics: if the trunk characteristics at both ends do not match (e.g., trunk type or native VLAN does not match), no trunk connection will be established and the interface will remain as an access-link connection. When using mode no-negotiate, the established trunk connection may fail if the trunk characteristics at both ends do not match.Table 12.5 Conditions for Establishing Trunk Connections Current Switch _________________ Remote SwitchKeep the DTP information listed in Tables 12.4 and 12.5 in mind when preparing for the exam. a successful DTP will establish an 802.1Q trunk connection.When using DTP autodetection, a native VLAN mismatch error will occur if the native VLAN does not match.2. Configuring Switch TrunkingConfigure trunking on the 2960 switch in the same manner as most Cisco IOS switches.switch(config)# interface type slot_#/port_# switch(config-if)# switchportmode trunk|dynamic desirable| dynamic auto|nonegotiate switch( config-if)# switchporttrunk native vlan VLAN_#Trunking is supported on all ports of the 2960 switch. Don't forget that the 2960 switch only supports 802.1Q trunking, so only trunk connections to other 802.1Q trunking devices can be configured. To set the trunk connection to on mode, use the parameter trunk; to set it to DTP mode desirable, use the parameter dynamic desirable; to set it to auto mode, use the parameter dynamic auto. default mode is auto. if you do not want to use DTP but want to perform trunking, use the parameter nonegotiateQ For 802.1Q trunking, the native VLAN defaults to VLAN1, but can be changed using the command switchport trunk native vlan; if you do so, make sure that all switches in the Layer 2 network have the same native VLAN. If two switches connected through a trunk connection have different native VLANs, traffic from one VLAN on one switch will go to the other VLAN on the other switch, which can lead to various problems.