Innovative Technologies

Change the trunking encapsulation on SW1’s inter-switch links from static ISL to static 802.1q.

SW1(config)#int range Fa0/13 - 21
SW1(config-if-range)#switchport trunk encapsulation dot1q 

Verify that SW2, SW3, & SW4 are negotiating 802.1q as the trunking encapsulation to SW1, and that SW1 is not negotiating 802.1q to SW2, SW3, and SW4

SW1#sh int trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    802.1q         trunking      1
Fa0/14      desirable    802.1q         trunking      1
Fa0/15      desirable    802.1q         trunking      1
Fa0/16      desirable    802.1q         trunking      1
Fa0/17      desirable    802.1q         trunking      1
Fa0/18      desirable    802.1q         trunking      1
Fa0/19      desirable    802.1q         trunking      1
Fa0/20      desirable    802.1q         trunking      1
Fa0/21      desirable    802.1q         trunking      1

SW2#sh int trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/6       on           802.1q         trunking      1
Fa0/13      auto         n-802.1q       trunking      1
Fa0/14      auto         n-802.1q       trunking      1
Fa0/15      auto         n-802.1q       trunking      1

SW3#sh int trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      auto         n-802.1q       trunking      1
Fa0/14      auto         n-802.1q       trunking      1
Fa0/15      auto         n-802.1q       trunking      1

SW4#sh int trunk
Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      auto         n-802.1q       trunking      1
Fa0/14      auto         n-802.1q       trunking      1
Fa0/15      auto         n-802.1q       trunking      1