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Switchport mode trunk question

Hi Experts,

I have 2 switches. One is switch 3020 and the other one is switch 3750. The port 17 of switch 3750 is configured as trunking port, as below :

switchport trunk encapsulation dot1q

switchport mode trunk

speed 1000

duplex full

The other port 17 at Switch 3020, is configured as below:

interface fastethernet0/17

switchport access vlan 33

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

I have a server connected to port 15, vlan 31.

There is also virtual interface of vlan 31 at 3750 with hsrp standby ip.

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

The question is.. why I am still able to ping to the server from a user that connected to 3750 since the vlan at the trunking is only 33?

Thanks in advanced.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Switchport mode trunk question

The setting "switchport access vlan xxx" determines the vlan ID for the port WHEN it is in access mode. To hard-code it in acces mode you need to enter the command "switchport mode access" as well.

This setting widely recommended as a security measure for ports that you do not want to use as trunks. In this way you can prevent that the attachment of a switch allows access to any vlan in the network.

Leo

5 REPLIES

Re: Switchport mode trunk question

As you have not specified the port at the 3020 to be in access mode (switchport mode access) the default is in operation.

The default is auto-trunking; when a trunk is discovered on a port, a trunk is established.

You can verify this by checking: sh int ../17 switchport.

This will give you the operational trunking mode.

regards,

Leo

Community Member

Re: Switchport mode trunk question

Thanks Leo..so this trunking will also applied even when the switchport access vlan xxx is configured at the switchport ??

meaning it can take all the vlans numbering across right? ;)

Thanks again..

Re: Switchport mode trunk question

The setting "switchport access vlan xxx" determines the vlan ID for the port WHEN it is in access mode. To hard-code it in acces mode you need to enter the command "switchport mode access" as well.

This setting widely recommended as a security measure for ports that you do not want to use as trunks. In this way you can prevent that the attachment of a switch allows access to any vlan in the network.

Leo

Community Member

Re: Switchport mode trunk question

Thanks Leo..

Helpful reply.. :)

Have rated your post..

Regards,

Re: Switchport mode trunk question

Rating posts is always good.

Thanks a lot!!

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