A little confused with Hybrid Ports and Tagging on single stacks

[cyberspace]

For some reason I was under the impression that on a 5500 switch, only 1 vlan (when in hybrid mode) could be set as untagged.

However I see on the 4800 I can have several VLANs untagged.

When the switch is on it's own (that is, a single stack, no other switches to connect to), what is the benefit of tagged vs untagged?

I understand that generally tagging adds the 802.1Q header to give VLAN ID, etc, which is used over trunk links...but I am now a little confused over what it's doing on a single stack.

I work with the 3Com VCX and I always set up switches with hybrid ports with VLAN1 untagged and VLAN x (x = voice vlan id) tagged.

Would appreciate it if someone could clear up this particular scenario for me as it's just got me confused as to whether or not it actually does anythig when theres only 1 stack on a single site.

Thanks in advance

'When all else fails.......read the manual'

 

[cyberspace]

Ps - I forgot to add, that my present understanding is that an untagged packet just goes onto the native VLAN of the port, as per the ports PVID.

If I set the hybrid port to vlan 1 untagged and vlan 2 untagged, how will it know what to do with traffic on vlan 2?

'When all else fails.......read the manual'

 

[VinceWhirlwind]

I am not familiar with those switch models, but I have configured VLANs on many other 3COM and HP switches and I can not see either any reason to want multiple VLANs untagged on a single port, or in fact any way you could actually configure this.

When I configure a port to be "untagged" in 1 VLAN, it immediately removes it from being "untagged" in its existing VLAN.

 

[cyberspace]

It's quite odd. I wonder if it's a bug?

I tested this:

interface GigabitEthernet1/0/9
port link-type hybrid
port hybrid vlan 1 untagged
port hybrid vlan 7 untagged

And then if I do a look at the interface:

[4800G]dis int gig 1/0/9
GigabitEthernet1/0/9 current state: DOWN
IP Packet Frame Type: PKTFMT_ETHNT_2, Hardware Address: 4001-c62b-82c9
Description: GigabitEthernet1/0/9 Interface
Loopback is not set
Media type is twisted pair
Port hardware type is 1000_BASE_T
Unknown-speed mode, unknown-duplex mode
Link speed type is autonegotiation, link duplex type is autonegotiation
Flow-control is not enabled
The Maximum Frame Length is 9216
Broadcast MAX-ratio: 100%
Unicast MAX-ratio: 100%
Multicast MAX-ratio: 100%
Allow jumbo frame to pass
PVID: 1
Mdi type: auto
Link delay is 0(sec)
Port link-type: hybrid
Tagged VLAN ID : none
Untagged VLAN ID : 1, 7
Port priority: 0
<output cut>









'When all else fails.......read the manual'

 

[merrym]

Well, let´s write en email to 3com support and see what they say about this...

http://emea.3com.com/support/returns/forms/contact/

 

[cknipe]

I have always setup my Data/Voice configurations in the same way. However I have started to notice that I have not had much luch with this setup on the last 3 or 4 installs I have been on.

Now I just setup the port this way and it works just as well.


Trunk port
poe enable
port turnk permit vlan <data>, <voice>
port trunk pvid vlan <data>


something like that should do the trick.