200-301 cisco certified network associate book

200-301 cisco certified network associate book.Column Position Title ReasonFirst column . VLANs allowed VLANs 1-4096, except those removed by the switchport trunk allowed commandSecond column VLANs allowed and valid First list, except those not defined as local switches or in shutdown modeColumn 3 Second list of VLANs located in SPT, except STP blocking and VTP removal interfacesYou should also check the trunk's native VLAN configuration in this step. Using the switchport trunk native vlanvlan-id command, the native VLANID can be manually set to a different VLAN at either end of the trunk. if the native VLAN is inconsistent, the switch will randomly cause frames to leave one VLAN and enter another VLAN later.For example, switch SW1 sends a frame on an 802.1Q trunk using the local VLAN1. SW1 does not add a VLAN header, which is normal for the local VLAN. And when switch SW2 receives this frame and finds that the 802.1Q header is missing, SW2 assumes that the frame belongs to the local VLAN configured by SW2. if previously configured SW2 considers VLAN2 to be the local VLAN on this trunk, SW2 attempts to forward the received frame toward VLAN2.Finally, check that the interface that is supposed to be trunked is not trunked. The most likely cause of this problem is a misconfiguration of port aggregation (Trunking) on the other end of the link. the switchport mode {access | trunk | dynamic {desirable | auto}} interface subcommand can tell whether the interface is trunked and the rules for negotiating port aggregation (Trunking). You can also use the show interfaceswitchport command to display the administrative (configured) port aggregation (Trunking) mode (set using the previous configuration command) for any interface.Be sure to understand the meaning of each configuration command option; the worst combination is to use the dynamic auto option on both ends of the link, which happens to be the default setting on some Cisco switches. If neither end has the switch set up, both ends will be negotiating port aggregation (Trunking) when one end starts processing. So both ends will wait and no trunking will be established (Trunk). Table 3-7 lists the options for the switchport trunk mode command and the corresponding resulting port aggregation (Trunking) mode.Table 3-7 Expected Port Aggregation (Trunking) Operation Modes Based on the Configured Management ModeManagement Mode Access Dynamic Auto Trunk Dynamic Desirable