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hp switches

Posted on 2014-02-14
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Last Modified: 2014-03-17
Hello,
I have a new hp 48port switch.
Can someone please explain to me (elementary) what does "tagged", "untagged" and "no" is all about when it comes to setting up vlans.
I read online forums for the difference between tagged and untagged but I still don't get it and confused.
please use examples if possible.
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Question by:MrMay
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Expert Comment

by:Infamus
ID: 39860200
If you only have one switch, all the ports should be untagged.

You only need tagging when you connect two or more switches so that the vlans can be tagged and seen by the other switch.

Let's say you have vlan 5 and vlan 10

vlan5 untag ports 1-12
vlan10 untag ports 13-23

If you connect port 24 to other switch, then you can

vlan5 tag port 24
vlan10 tag port 24

I just tried not to be technical.
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Author Comment

by:MrMay
ID: 39860219
this switch connects to another switch.
i"m looking at the old configuration on this switch and it has the following:

virtual vlan . ID#1
port 1 - 15 and 17-28 = untagged
port 16 = no

voice vlan. ID#4
port 1 -15, 17-25, and 27-28 = no
port 16 = untagged
port 26 = tagged.

I'm just not sure why its like this... what does untagged and tagged mean? when do I use each one? how do I know when to use each one and when do I use "no"?
please explain.
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Assisted Solution

by:Infamus
Infamus earned 428 total points
ID: 39860268
virtual vlan . ID#1
port 1 - 15 and 17-28 = untagged
port 16 = no          <-----------------------Port 16 is not on vlan ID#1 and belongs to vlan ID#4

voice vlan. ID#4
port 1 -15, 17-25, and 27-28 = no  <---Port 1-15, 17-25 is not on vlan ID#4 and belongs to vlan ID#1

port 16 = untagged

port 26 = tagged.     <--------vlan ID#4 will be tagged to the switch that is connected to port 26.
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Expert Comment

by:jburgaard
ID: 39860572
'Tag' is short for IEEE 802.1Q-tag. That is a way to handle virtual LAN's (vlans) .
Between switches you would like to transport more vlans in one link.
This is done by the switches adding info to the packets flowing between them, this info is called a TAG.
On the other hand on the ports to hosts (PC's etc) the switches should be able to deal with only one of these vlans in a way understandable for a host. (normal short packets without these TAG's)
So here packets on a witch-port to and from a PC belonging to certain vlan flow without TAGs (=UNtagged)

http://en.wikipedia.org/wiki/IEEE_802.1Q
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Expert Comment

by:jburgaard
ID: 39860619
When you should use what.
Port to pc, printer etc.: UNtag in one vlan (no tagging here)
(Port to Phone could eventually be untagged in one vlan and tagged in an other)

Ports between switches that must carry more vlans could on HPProcurves
a) TAG all vlans to be carried  OR
b) Untag one of them and TAG the rest
Important: both ends must match (same pattern of TAGing)
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Author Comment

by:MrMay
ID: 39860844
infamous, one other question.  if port 26 is tagged(in voice vlan) since its the upload port from the other switch, how come its not tagged on the default vlan?
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by:jburgaard
jburgaard earned 72 total points
ID: 39861208
"virtual vlan . ID#1
port 1 - 15 and 17-28 = untagged"
-meaning packets without TAG on port 26 are belonging to vlan 1

IF the port on the other switch linking to port 26 is set up in exact the same way,
that is UNtag vlan1 &TAG vlan 4 , then the switches can exchange packets both in vlan1 and vlan4.
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Author Comment

by:MrMay
ID: 39870930
I started reading about loop-protection on ports.
from the internet I got "when a switch sends out a loop protocol packet and then receives the same packet on a port that has receiver-action of send-disable configured, it shuts down the port from which the packet was sent".

can some one please explain this to me using an example. cause to me this sounds like a collision-domain.
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by:Infamus
Infamus earned 428 total points
ID: 39870943
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Author Comment

by:MrMay
ID: 39871317
good article infamus.
the first explanation throws me off a bit.
A Network Loop is the result of network switches or hubs being plugged into themselves or into each other more then once
this means that switch 1 is pluged into switch 2 and switch 3 is plugged into switch 1, right?
it doesn't mean that switch 1 and switch 2 are connected to each other with two Ethernet cables, right?    
I'm sorry if these are really dump question, I'm trying to learn this.
I mean, how can and why would you plug a switch into itself???
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by:Infamus
Infamus earned 428 total points
ID: 39871340
this means that switch 1 is pluged into switch 2 and switch 3 is plugged into switch 1, right?
No, what you said is normal.
someone who has no idea can plug in a cable into, let's say, port 5 and port 10 on a same switch with single cable is what it means by network switches or hubs being plugged into themselves.

it doesn't mean that switch 1 and switch 2 are connected to each other with two Ethernet cables, right?  
No, this is what actually "or into each other more then once."
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Author Comment

by:MrMay
ID: 39871553
so an admin can by mistake actually plug switch A to switch B with two cables?????
Example; switch A port1 connects to switch B port 2 and then Switch A port3 into switch B port5....
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by:Infamus
Infamus earned 428 total points
ID: 39871565
Normally, you use port-channel when you connect two cables from one another.
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Author Comment

by:MrMay
ID: 39871946
so port-channel is used for redundancy? please explain
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by:Infamus
Infamus earned 428 total points
ID: 39871954
Yes, for redundancy and for more bandwidth.

Let's say you have a 1Gb switch and you can connect two cables with port channel and you will get 2Gb of bandwidth.
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Author Comment

by:MrMay
ID: 39871990
so if I make one logical connection using two Ethernet cables, the switch just sees one connection?
if this is the case how does this create a loop?
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Accepted Solution

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Infamus earned 428 total points
ID: 39872021
Yes, it is one logical connection called interface port-channel and this connection itself won't create a loop.

If it is not bonded with port-channel, it might create a loop.
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Author Comment

by:MrMay
ID: 39872045
got it  :-)
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