Cisco Trunking Configuration Basic

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More information will be added in short.

 

Trunking Protocol
– Form between Switch and PCs or Switch and Switch.
– Tagging(VLAN ID)

1. ISL
– Cisco proprietary
– Change origin frame
– Attach ISL dedicated 26bytes header in front of origin frame.
– VLAN info at ISP header
– Not support old devices such as hub.

Cisco Catalyst 1900 : ISL only
Cisco Catalyst ~ 2924 : ISL and dot1q
Cisco Catalyst 2950 : dot1q only
Cisco Catalyst 3550 : isl and dot1q
Cisco Catalyst 2924, 3550
switch(config)# interface fastethernet 0/24
switch(config-if)# switchport turnk encapsulation isl
switch(config-if)# switchport mode trunk

 

2. 802.1q (dot1q)
– IEEE standard
– Most of vendor
– Origin flame won’t be changed
– Support leggacy by Native vlan

Catalyst 3550
switch(config)# interface fa 0/3
switch(config-if)# switchport trunk encapsulation dot1q
switch(config-if)# switchport mode trunk

Catalyst 2950
switch(config)# int fa 0/3
switch(config-if)# switchport trunk encapsualtion dot1q
Error
why?
Be cause Catalyst 2950 is only support dot1q, so no syntex availialbe

Just type
switch(config-if)# switchport mode trunk

 

SWITCH# conf t
SWITCH(config)# int fa 1/3
SWITCH(config-if)# description trunking configuration basic
SWITCH(config-if)# switchport
SWITCH(config-if)# switchport trunk encapsulation dot1q
SWITCH(config-if)# switchport mode trunk
SWITCH(config-if)# switchport trunk allowed vlan add 1-10
SWITCH(config-if)# switchport trunk allowed vlan remove 5
SWITCH(config-if)# end
SWITCH#

 

 

Before enble Trunk

Name: Fa1/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access (member of bundle Po1)
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Disabled
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: none
Priority for untagged frames: 0
Override vlan tag priority: FALSE
Voice VLAN: none
Appliance trust: none

After enable Trunk

Name: Fa1/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk (member of bundle Po1)
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Disabled
Access Mode VLAN: 0 ((Inactive))
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: none
Priority for untagged frames: 0
Override vlan tag priority: FALSE
Voice VLAN: none
Appliance trust: none Trunk on EtherChannel link

– It doesn’t matter one side is EtherChannel formed and other side is not.
– For example, Two switches are connected each other with 3 fastethernet connectiones. Switch A formed Port-Channel, but Switch B doesn’t have EtherChannel interface. Still trunking informaiton is passing also, two links are on forwarding stage thru Spanning Tree Protocols