vlan 1 not allowed on a trunk

Answered Question
Apr 29th, 2010
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Hello,


I would like to not allow the vlan 1 on trunks.

The native vlan of those trunk could be this vlan 1.

We are using RSTP for several tagged vlans (with MAC addresses reduction).

and also CDP, UDLD

(cat4500,  IOS, sup6-E)


I'm looking for information about what is beeing send throuhgt this vlan 1 even if it is not allowed.


the link http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13   

section "The Case of VLAN 1"

gives some information about DTP, PAgP, CDP, VTP  but some others are not listed here.

Those protocols listed are used between the 2 directly connected neighboors.


Does someone have some more information  or links  ?



regards,

Correct Answer by Jon Marshall about 7 years 3 weeks ago

jabouaf wrote:


Hello Jon,


Thank you for the answerd.

So, those protocols  CDP/PagP/STP (for vlan 1)/VTP/UDLD   are still running even if  vlan 1 is cleared from the trunk

DTP will go on working, but on the native vlan . I 'forced' the trunk to on so it is ok. So I then can change the native vlan and remove from the trunk this vlan 1. Changes should be the same to the remote side of course.


the 'others protocols I was thinking are the ones that I don't know but are like  existing from the section "the case of vlan 1" of the link

http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13

"This pruning does not include all the control protocol traffic that is still allowed on the trunk (DTP, PAgP, CDP, VTP, and others)."

So I wonders what  those others protocols are ?


Thank you for your help.

regards,


You can also clear the native vlan off the trunk link and DTP will still work as well.


"Others" is just a catch-all i think for any other Cisco control protocols that get put on vlan 1. I'm not aware of any more other than the ones we have listed but you never know


Jon

Correct Answer by Jon Marshall about 7 years 4 weeks ago

jabouaf wrote:


Hello,


I would like to not allow the vlan 1 on trunks.

The native vlan of those trunk could be this vlan 1.

We are using RSTP for several tagged vlans (with MAC addresses reduction).

and also CDP, UDLD

(cat4500,  IOS, sup6-E)


I'm looking for information about what is beeing send throuhgt this vlan 1 even if it is not allowed.


the link http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13   

section "The Case of VLAN 1"

gives some information about DTP, PAgP, CDP, VTP  but some others are not listed here.

Those protocols listed are used between the 2 directly connected neighboors.


Does someone have some more information  or links  ?



regards,


Vlan 1 = CDP/PagP/STP (for vlan 1)/VTP/UDLD


were there any others you were thinking of ?


Native vlan = DTP


So if native vlan = vlan 1 then all of the above are on vlan 1. If the native vlan is not vlan 1 all the above are on vlan 1 except DTP which is on the native vlan.


If you clear both vlan 1 and the native vlan off a trunk it will not affect the above protocols being carried across a trunk link.


Jon

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Correct Answer
Jon Marshall Thu, 04/29/2010 - 11:21
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jabouaf wrote:


Hello,


I would like to not allow the vlan 1 on trunks.

The native vlan of those trunk could be this vlan 1.

We are using RSTP for several tagged vlans (with MAC addresses reduction).

and also CDP, UDLD

(cat4500,  IOS, sup6-E)


I'm looking for information about what is beeing send throuhgt this vlan 1 even if it is not allowed.


the link http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13   

section "The Case of VLAN 1"

gives some information about DTP, PAgP, CDP, VTP  but some others are not listed here.

Those protocols listed are used between the 2 directly connected neighboors.


Does someone have some more information  or links  ?



regards,


Vlan 1 = CDP/PagP/STP (for vlan 1)/VTP/UDLD


were there any others you were thinking of ?


Native vlan = DTP


So if native vlan = vlan 1 then all of the above are on vlan 1. If the native vlan is not vlan 1 all the above are on vlan 1 except DTP which is on the native vlan.


If you clear both vlan 1 and the native vlan off a trunk it will not affect the above protocols being carried across a trunk link.


Jon

jabouaf Thu, 05/06/2010 - 08:59
User Badges:

Hello Jon,


Thank you for the answerd.

So, those protocols  CDP/PagP/STP (for vlan 1)/VTP/UDLD   are still running even if  vlan 1 is cleared from the trunk

DTP will go on working, but on the native vlan . I 'forced' the trunk to on so it is ok. So I then can change the native vlan and remove from the trunk this vlan 1. Changes should be the same to the remote side of course.


the 'others protocols I was thinking are the ones that I don't know but are like  existing from the section "the case of vlan 1" of the link

http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13

"This pruning does not include all the control protocol traffic that is still allowed on the trunk (DTP, PAgP, CDP, VTP, and others)."

So I wonders what  those others protocols are ?


Thank you for your help.

regards,

Correct Answer
Jon Marshall Thu, 05/06/2010 - 09:03
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

jabouaf wrote:


Hello Jon,


Thank you for the answerd.

So, those protocols  CDP/PagP/STP (for vlan 1)/VTP/UDLD   are still running even if  vlan 1 is cleared from the trunk

DTP will go on working, but on the native vlan . I 'forced' the trunk to on so it is ok. So I then can change the native vlan and remove from the trunk this vlan 1. Changes should be the same to the remote side of course.


the 'others protocols I was thinking are the ones that I don't know but are like  existing from the section "the case of vlan 1" of the link

http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic13

"This pruning does not include all the control protocol traffic that is still allowed on the trunk (DTP, PAgP, CDP, VTP, and others)."

So I wonders what  those others protocols are ?


Thank you for your help.

regards,


You can also clear the native vlan off the trunk link and DTP will still work as well.


"Others" is just a catch-all i think for any other Cisco control protocols that get put on vlan 1. I'm not aware of any more other than the ones we have listed but you never know


Jon

jabouaf Thu, 05/06/2010 - 09:12
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Hello Jon,


Thank you for this information (porecision ?).


Best regards,

Jean-David

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