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Why me core switch port becomes tagged & untagged

deepoce
Occasional Visitor

Why me core switch port becomes tagged & untagged

Can a port become tagged & untagged at the same time?

What it actually means?

In cisco,port can be either access or trunk not both! Right? Can someone advise & help?



Unit 1, Port 18 Detailed Information



StpState: Enabled fwdTransitions: 4

StpCost: 18 BroadcastStormControl: Enabled

StpFastStart: Disabled QoS Profile: 2

DefaultPriority: 0

LACP State: Disabled

LACP PartnerID: Not known



VLAN ID VLAN Name Tagging Mode Spanning Tree

------------------------------------------------------

1 Default VLAN Tagged Forwarding

5 Restricted Tagged Forwarding

6 Users Untagged Forwarding

13 SiBS Tagged Forwarding



===================================================





Unit 1, Port 6 Detailed Information



StpState: Enabled fwdTransitions: 0

StpCost: 4 BroadcastStormControl: Enabled

StpFastStart: Disabled QoS Profile: 2

DefaultPriority: 0

LACP State: Disabled

LACP PartnerID: Not known



VLAN ID VLAN Name Tagging Mode Spanning Tree

-----------------------------------------------------1 Default VLAN Untagged Disabled

13 SiBS Tagged Disabled

3 REPLIES
Shirin
Frequent Advisor

Re: Why me core switch port becomes tagged & untagged

Yes, that is what it is called 802.1Q or a 802.1Q compliant trunk = port tagged in vlan x and untagged in vlan y or a port untagged in vlan x @ t=0 and at t=0+1 tagged in vlan y

in 3Com you can achieve such using trunk or using hybrid link type

In cisco the 'trunk' port is not necessary 802.1Q compliant since it can be a cisco trunk or a cisco ILS

regards.

This message was edited by Shirin on 3-9-09 @ 1:25 AM
Rob_Korn
Advisor

Re: Why me core switch port becomes tagged & untagged

If you mix tagged/untagged on same port, it is "hybrid".



Please note there is a way to force traffic that has no vlan id into a vlan. This is the "PVID" or Native vlan.



In short, you may have any packets that have NO vlan go to a special vlan for different processing or routing.



Rob.

Lisandro
Occasional Visitor

Re: Why me core switch port becomes tagged & untagged

In a port, you can set different vlans to pass trough. To enable this feature, you must enter the port´s interface, and ser the port link-type to hybrid.

There (check the switch manual) you can set TAGGED vlan traffic, and UNTAGGED vlan traffic.



For example: witch 5500-EI 52ports. On port 52 (gigabit ethernet) i want to pass traffic from 2 different vlans: vlan 1 and vlan 1000. Traffic comming from/to vlan 1000 must be visible on port 48 (wich belongs to vlan 1000)



You must enter:

interface gigabitethernet1/0/52

port link-type hybrid (were are telling more than one vlan is passing trough)

port hybrid vlan 1 untagged (thsi vlan´s traffic won´t be marked)

port hybrid vlan 1000 tagged (this vlan´s traffic must be tagged - marked - using 802.11Q)

port hybrid pvid vlan 1 (native vlan)



I hope you can understand! My english is very poor.



Regards.



Lisandro.