Vlan carrying

[Monsinka]

hello, 

if i have one vlan configured exp:vlan 100 , and i need to carry the vlan between SW1=> SW2 =>SW3 , the vlan is defined on all the 3 switchs the interco between those switchs need to be trunk or access ? , even if its only one vlan? 

[Mark Elsen]

   - @Monsinka     If the links carries only one vlan then you don't need a trunk, but don't use access mode,
                            set the ports to default, and them put them in vlan 100

  M.

[Monsinka]

so i dont need to specify the type of the link ( access or trunk ) like this : int g0/0 #switchport switchport access vlan 100 without switchport mode access ? will it work ? 

[Mark Elsen]

   - @Monsinka                           Yes , that will work

  M.

[Joseph W. Doherty]

As @Mark Elsen has already described, for one VLAN you don't need a trunk.  (BTW, on most non-ancient Cisco switches you can convey two VLANs without a trunk too.)

[Giuseppe Larosa]

Hello @Monsinka ,

inter switch links SW1 <->SW2 and SW2 <->SW3 don't need to be trunk port, however it is highly recommended to use trunk ports because it is easy to add new VLANs on the path when needed.

Also note that Cisco switches with DTP Dynamic Trunking Protocol had a default behavior to negotiate a trunk link even if not configured if some parameters match ( including VTP domain name) with default settings and DTP state.

So you may have a trunk even if not manually configured.

you can check using show commands like 

show interface trunk 

or

show interface switchport

Hope to help

Giuseppe