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Confirming when 'allow trunk' info will be visible

Hi, I noticed that on my 2950 switches, sometimes I Configure trunk allowing certain vlans, but then I do show run and the 'switchport trunk allowe vlan x,y' info is not visible.

That should come up once ports are enabled on both sides of the trunk, right? Is that a bug or a by design feature on the IOS? Strange...

Current configuration : 122 bytes

!

interface FastEthernet0/23

description gw1

switchport mode trunk

no keepalive

shutdown

speed 100

duplex full

end

myswitch#config t

Enter configuration commands, one per line. End with CNTL/Z.

myswitch(config)#int f0/23

myswitch(config-if)#switchport trunk allow vlan add 7

myswitch(config-if)#switchport trunk allow vlan add 4

myswitch(config-if)#shut

myswitch(config-if)#

myswitch#wri mem

Building configuration...

[OK]

myswitch#show run int f0/23

Building configuration...

Current configuration : 122 bytes

!

interface FastEthernet0/23

description gw1

switchport mode trunk <=========== see that vlans are not visible.

no keepalive

shutdown

speed 100

duplex full

end

myswitch#show vlan

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/22, Fa0/23

4 VLAN0004 active

7 Ma1 active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16

Fa0/17, Fa0/18, Fa0/19, Fa0/20

Fa0/21

1002 fddi-default act/unsup

1003 token-ring-default act/unsup

1004 fddinet-default act/unsup

1005 trnet-default act/unsup

VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2

---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------

1 enet 100001 1500 - - - - - 0 0

4 enet 100004 1500 - - - - - 0 0

7 enet 100007 1500 - - - - - 0 0

1002 fddi 101002 1500 - - - - - 0 0

1003 tr 101003 1500 - - - - - 0 0

1004 fdnet 101004 1500 - - - ieee - 0 0

myswitch#5~

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Bronze

Re: Confirming when 'allow trunk' info will be visible

The command you are using is useful when you pruned those Vlans beforehand either with VTP Pruning or with an 'allow except' option.

By default, all Vlans are allowed in a trunk so using the 'add' keyword won't do anything to the config.

If you want to allow just 4 and 7 on the trunk, the command is:

switchport trunk allowed vlan 4,7

HTH,

__

Edison.

1 REPLY
Hall of Fame Super Bronze

Re: Confirming when 'allow trunk' info will be visible

The command you are using is useful when you pruned those Vlans beforehand either with VTP Pruning or with an 'allow except' option.

By default, all Vlans are allowed in a trunk so using the 'add' keyword won't do anything to the config.

If you want to allow just 4 and 7 on the trunk, the command is:

switchport trunk allowed vlan 4,7

HTH,

__

Edison.

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