Campus, Configuration, Dell EMC Networking, Support & Troubleshoot

PowerConnect Switchport modes

.

This post gives a comparison between the different port modes available on the Dell PowerConnect switches. the trunk and access modes are familiar to anyone who understands tagged and untagged transmission, the general mode however allows a lot more flexibility with port configurations.


      • Trunk: all packets transmitted are tagged.  Untagged received traffic is dropped.  Tagged received traffic is dropped if it is not tagged in one of the member vlans. with later firmware versions, i have observed the switches to allow reception of untagged traffic, but not transmission. Thus, courtesy this behavior, the trunk port can now have an effective native vlan.
      • Access: all packets are transmitted untagged.  Untagged received traffic is accepted and switched in the ports define vlan.  Tagged received traffic is dropped.
      • General: can be configured to transmit tagged or untagged traffic per vlan.  Untagged received traffic is accepted and switched in the defined PVID.  Tagged received traffic is dropped if it is not in one of the port’s tagged vlans.

So this:

switchport mode access

switchport access vlan 99

Is equivalent to this:

switchport mode general

switchport general allowed vlan add 99 untagged

switchport general pvid 99

And this:

switchport mode trunk

switchport trunk allowed vlan add 99,100

Is equivalent to:

switchport mode general

switchport general allowed vlan add 99,110 tagged

switchport general pvid 4095             (this is the drop vlan)

.

About Hasan Mansur

Hasan Mansur --------------------- bis vincit qui se vincit in victoria.

Discussion

4 thoughts on “PowerConnect Switchport modes

  1. AoA…

    brother can you please elaborate pvid concept hete.. is it reference towards PRIVATE Vlans ?

    Posted by Anonymous | April 12, 2013, 10:22 am
  2. WS

    You can think of pvid as a declaration of “Native” or “Untagged” VLAN on the port. General mode is only a variation of trunk ports.

    On Powerconnect switches, trunk port only allows transmission of tagged frames, but no untagged frames (It would however, allow reception of untagged frames at ingress, which are switched in the default vlan on the port). General mode, though, allows both tagged and untagged frames for both ingress and egress.

    When you compare this to Cisco, trunk mode on Cisco can allow both tagged and untagged frames to be configured on a port. therefore, you can say the powerconnect mode general is actually what a trunk mode on Cisco is.

    A Cisco trunk port is assigned a default port VLAN ID (PVID) for a VLAN on which all untagged traffic will travel. Any untagged or tagged traffic with a NULL (unassigned) VLAN ID, is assumed to belong to the VLAN with the port default PVID. The equivalent Cisco command for declaring pvid on a trunk link (.1Q) would be “switchport trunk native VLAN xx”

    Porting this to Powerconnect, the above is true for the behavior of a “general” port. the pvid is declared through the command “Switchport general pvid xx”. one command i find particularly helpful in determining port behavior for VLAN tagging is “show interface switchport gigabit/tengig xx”, which breaksdown the membership and tagging behavior nicely for you on the Powerconnect switches.

    hope this helps, but if not, please do flag and i shall be happy to advise further.

    Posted by Hasan Mansur | April 13, 2013, 1:10 pm
  3. Dude THANK YOU. I come from CISCO, i had no idea why I couldn’t get my management VLAN through on these dells.

    Posted by Larry | February 4, 2014, 10:52 pm
  4. Your article helped me resolve a big issue with the wireless access in my new workplace; the switches had not been configured correctly for multiple VLANs. Thank you very much!

    Posted by DT | February 7, 2014, 8:04 pm

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: