CCIE Pursuit Blog

August 8, 2007

Configuring 802.1q Trunks Between 3560s

Filed under: Cisco,Cisco Certification,IOS,Switching — cciepursuit @ 10:17 am

Task: Configure an ISL trunk link between sw1 and sw2.  (Both switches are 3560s)

sw1 (3560) fa0/13—————–fa0/13 sw2 (3560)

I can think of 6 different ways to accomplish this task:

1) Hardset both switchports to trunk
2) Hardset one switchport to trunk and set the other to use DTP dynamic auto(default)
3) Hardset one switchport to trunk and set the other to use DTP dynamic desirable
4) Configure one switch to use DTP dynamic auto with dot1q encapsulation and set the other to use DTP dynamic desirable.
5) Configure one switch to use DTP dynamic desirable with dot1q encapsulation and set the other to use DTP dynamic desirable.
6) Configure one switch to use DTP dynamic desirable with dot1q encapsulation and set the other to use DTP dynamic auto(default).

Note: Trivial solutions can be achieved with “switch nonegotiate” and I’m not touching dot1q tunneling in this post.  🙂


1) Hardset both switchports to trunk:

sw1:
sw1#sh run int fa0/1
Building configuration…

Current configuration : 33 bytes
!
interface FastEthernet0/1
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      on           802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 95 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      on           802.1q         trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

2) Hardset one switchport to trunk and set the other to use DTP dynamic auto(default):

sw1:
sw1#sh run int fa0/13
Building configuration…

Current configuration : 95 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      on           802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 34 bytes
!
interface FastEthernet0/13
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      auto         n-802.1q       trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

3) Hardset one switchport to trunk and set the other to use DTP dynamic desirable:

sw1:
sw1#sh run int fa0/13
Building configuration…

Current configuration : 95 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      on           802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
—-output truncated—-

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 69 bytes
!
interface FastEthernet0/13
 switchport mode dynamic desirable
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    n-802.1q       trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

4) Configure one switch to use DTP dynamic auto with dot1q encapsulation and set the other to use DTP dynamic desirable:

sw1:
sw1#sh run int fa0/13
Building configuration…

Current configuration : 72 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      auto         802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 69 bytes
!
interface FastEthernet0/13
 switchport mode dynamic desirable
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    n-802.1q       trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

5) Configure one switch to use DTP dynamic desirable with dot1q encapsulation and set the other to use DTP dynamic desirable:

sw1:
sw1#sh run int fa0/13
Building configuration…

Current configuration : 107 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode dynamic desirable
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 69 bytes
!
interface FastEthernet0/13
 switchport mode dynamic desirable
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    n-802.1q       trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

6) Configure one switch to use DTP dynamic desirable with dot1q encapsulation and set the other to use DTP dynamic auto(default):

sw1:
sw1#sh run int fa0/13
Building configuration…

Current configuration : 107 bytes
!
interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode dynamic desirable
end

sw1#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      desirable    802.1q         trunking      1
—-output truncated—-

sw1#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

sw2:
sw2#sh run int fa0/13
Building configuration…

Current configuration : 34 bytes
!
interface FastEthernet0/13
end

sw2#sh int fa0/13 trunk

Port        Mode         Encapsulation  Status        Native vlan
Fa0/13      auto         n-802.1q       trunking      1
—-output truncated—-

sw2#sh int fa0/13 switch
Name: Fa0/13
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
—-output truncated—-

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1 Comment »

  1. […] Configuration For 802.1q Trunk Building on this post, let’s explore a favorite type of lab task –  the dreaded ”minimum configuration””  […]

    Pingback by Minimum Configuration For 802.1q Trunk « CCIE Pursuit — August 8, 2007 @ 10:32 am | Reply


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