Trunking troubleshooting commands

conf t

default int range fa 0/1-5
int range fa 0/1-5
shutdown
exit

! SW1-auto, SW2-auto
int fa 0/2
switchport trunk encap dot1q
switchport mode dynamic auto
no shutdown

do show int trunk

do show int fa 0/2 switchport | ex private|Unknown

shutdown
exit

! SW1-desirable, SW2-auto
int fa 0/2
switchport trunk encap dot1q
switchport mode dynamic desirable
no shutdown

do show int trunk

! Ping SW2 over VLAN 10
do ping 192.168.1.2

! Ping SW2 over VLAN 20
do ping 192.168.2.2

do show int fa 0/2 switchport | ex private|Unknown

shutdown
exit

! SW1-auto, SW2-ON
int fa0/4
switchport trunk encap dot1q
switchport mode dynamic auto
no shutdown

do show int trunk

! Ping SW2 over VLAN 10
do ping 192.168.1.2

! Ping SW2 over VLAN 20
do ping 192.168.2.2

do show int fa 0/4 switchport | ex private|Unknown

! Chaning native VLAN on 1 side:
switchport trunk native vlan 20

do show int trunk

! Ping SW2 over VLAN 10
do ping 192.168.1.2

! Ping SW2 over VLAN 20
do ping 192.168.2.2 repeat 2

shutdown
exit
default int fa 0/4

! SW1 On/Nonegotiate, SW2-On
int fa 0/4
switchport trun encap dot1q
switchport mode trunk
switchport nonegotiate
no shutdown

do show int trunk

do show int fa 0/4 switchport | ex private|Unknown

! Ping SW2 over VLAN 10
do ping 192.168.1.2

! Ping SW2 over VLAN 20
do ping 192.168.2.2

shutdown
exit

! SW1-On/Nonegotiate, SW2-dynamic desirable
int fa 0/3
switchport trun encap dot1q
switchport mode trunk
switchport nonegotiate
no shut

do show int trunk

do show int fa 0/3 switchport | ex private|Unknown

shutdown
exit

! Flipside:

! SW1-dynamic des, SW2-On/Nonegotiate
int fa 0/5
switchport trun encap dot1q
switchport mode dynamic desirable
no shutdown

do show int trunk

do show int fa 0/5 switchport | ex private|Unknown

shutdown
exit

! SW1-On/Nonegotiate, SW2-On/Nonegotiate
int fa 0/5
switchport trun encap dot1q
switchport mode trunk
switchport nonegotiate
no shut

do show int trunk

do show int fa 0/5 switchport | ex private|Unknown

! Ping SW2 over VLAN 10
do ping 192.168.1.2

! Ping SW2 over VLAN 20
do ping 192.168.2.2

shutdown
exit