p-Class GbE2 Switch question

[Stuart Teo]

I have a p-Class GbE2 Switch and I have a question regarding vlan tagging.

I have port 1 (blade 1, NIC1) tagging enabled and I noticed that the port started tagging even for the default PVID. Is this the correct behavior? I thought that the default PVID is always not tagged????????

Thanks.

[Oleg Koroz]

Is that new configuration? Or you did some changes with VLAN

From: Application Guide

The default configuration settings for GbE2 Interconnect Switches have all ports set as
untagged members of VLAN 1 with all ports configured as PVID = 1.

[Stuart Teo]

nope, i do not have the factory settings.

on top of vlan 1 that came with factory defaults, i added vlan 248 and vlan 249.

i then set port 1 to default itself to pvid 248 and everything worked fine. but the moment i enable tagging, the port started tagging. my question is: isn't the default pvid supposed to be untagged at all times?

but based on my tcpdump results, it doesn't seem to be that way. the application guide isn't too clear.

[Connery · Accepted solution]

(thread duplicated in "networking-switches,hubs,modems)

Hwee Liang Teo,

The GbE2 tags all VLANs - including the default/native VLAN when tagging is enabled on a port.

Cisco by default does not tag the native VLAN but they do provide a command to tag the native if desired (vlan dot1q tag native).

There is a slight difference between GbE2 tagging the native and Cisco tagging the native VLAN. Even with the GbE2 tagging the native VLAN, it will still accept untagged frames and classify the frames as the native VLAN ID (PVID). Whereas with Cisco, when you enable tagging of the native VLAN, all untagged frames are dropped.

Tagging of the native VLAN is actually safer. If you have different native VLANs accidentally configured on both sides of a point to point link, tagging the native VLAN will still allow all traffic to pass without getting classified as the wrong VLAN.

Bottom line is that it shouldn't cause any problems. If anything, it will prevent problems.

Regards,
-sean

[Stuart Teo]

Sean,

Thanks for the explanation but I find that port 1-16 seem to behave differently from port 19-24.

On ports 19-24, native VLAN isn't tagged.

On ports 1-16, native VLAN is tagged.

I need to find documentation regarding this, I've downloaded all the PDFs I can find but still don't seem to find anywhere that states this behavior.