By reading Cisco's manual at http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli_rel_4_0_1a/CLIConfigurationGuide/AccessTrunk.html it says that a port can be only 2 types and nothing else:

1, An access port can have only one VLAN configured on the interface; it can carry traffic for only one VLAN. 
   - Access port can be configured as > HOST port
2, A trunk port can have two or more VLANs configured on the interface; it can carry traffic for several VLANs simultaneously. 

I run into a lot of interesting devices like Zyxel, Dlink, Allied-telesis which had weird options such as a port can be:

1, Access
2, Trunk
3, General

What does General means? Would it be some AUTO-MAGIC=auto-fail feature that it tries to auto-detect it?

My other problem is that I have to link switches which although support VLANs they don't have any option to configure TRUNK ports (which would transfer multiple VLAN infos on the same cable).

So regardless that these switches are internally support 4096 VLAN, it seems to me that they cannot work together with other different type of switches which are VLAN capable. They don't have any port specific settings like I previously mentioned, you can only define different VLANs and add ports to them to be either tagged or untagged.


For example if the left switch supports trunking and I set port 15 to be TRUNK and plug it into the second switch port 1 (which as I said cannot be set to any mode) but on the second switch I manually create all the VLANs and add port 1 to be the member of any of them (as a trunk should be) what can be expected? Will this behave like a regular trunk?

I just run into lots of different problems with it, like I see traffic coming from those vlans with tcpdump but when I replug a machine, trying to move it to the new switch it's unreachable.

Any tips are welcome!

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    Watch the terminology CAREFULLY - while network is broadly standardised, wording, descriptions and implementation differ between vendors. This may well be part of your confusion - any switch that can support VLANs can support your definition of a trunk port, else, like you say, it'd be all but useless. Some vendors (Such as HP) use the term "VLAN Tagging" which is basically the same as Cisco's trunk port. – Dan Jul 28 '14 at 14:43

Basically, Dan's comment above contains all I think you need by way of an answer.

CISCO use the term trunk differently from some other vendors; to them it means a port that accepts packets on two or more VLANs, distinguished by 802.1q tags.

On products made by vendors who use the term trunk to mean something else (often the combination of one or more physical ports into a single logical connection, given appropriate cabling), you can regard a port which is a member of two more more VLANs to be equivalent.

As long as the permitted VLANs on the CISCO trunk match the permitted VLANs on the other switch's attached port, all should, in my experience, be fine.

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  • I'm sorry but no matter how I try the VLANs doesn't work on the second switch (which has no designated TRUNK port). TRUNK isn't equivalent with creating X identical VLANs and assigning port 1 to be a tagged port for all of these VLANs. – penguin2 Jul 28 '14 at 15:25
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    In my experience, it is. Can you mirror the attached-to-CISCO-trunk port on the second switch, and if so, what traffic do you see coming in on it? Which particular vendor are we talking about for this second switch, and apart from putting in several VLAN groups, how else have you configured the attached-to-CISCO-trunk port? – MadHatter Jul 28 '14 at 15:54
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    As @MadHatter says, assigning ports to a trunk port is the same as "tagging" them on other vendors. Essentially, so long as the traffic is being sent, tagged, down that port and the VLAN numbers match then it should work. – Dan Jul 28 '14 at 16:06

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