VLAN 1 question

[wabob]

We have a network with a dozen (or so) 3750s in a ring as the backbone. They all have the IP Services image so they can all route OSPF. Each 3750 has a few 2940s and 2950s downstream, some of the 2950s bridge between two 3750s for redundancy.

Is it possible to prune VLAN 1 on the trunks in the backbone ring? If so, are there any adverse side effects?

Experience is a tough teacher.
The test comes first, the lesson comes later...

 

[vipergg]

You should be able to prune vlan 1 off the trunks as long as none of your switches are using vlan 1 as their management vlan . Other functions such as cdp and vtp if used still use vlan1 to pass their information you just can not pass data when it is pruned off . On trunks it is best practice to prune anything that is not needed off .

 

[wabob]

None of the switches have VLAN 1 as the interface for their IP address.

If VLAN 1 is pruned on the uplink trunk, will I still be able to telnet to the switch, and have CDP / SNMP functionality? All our switches are in VTP transparent mode, so I don't think VTP is an issue.

Experience is a tough teacher.
The test comes first, the lesson comes later...

 

[vipergg]

Yes you will still be able to get to them if they aren't using vlan 1 as management , cdp will still function and it should have no effect on snmp...

 

[NetworksMD]

I don't believe VLAN 1 can be pruned as it is set to never be eligible for pruning.

 

[vipergg]

I would disagree on most of cisco modern switches you can manually prune vlan 1 off the trunk if wanted...

 

[rainman]

You sure about that? I thought VLAN 1 carried the VTP trunk information, and without that you'd have no VTP? Maybe I'm thinking about it wrong... I know I tried to eliminate VLAN 1 on a trunk before and it would not let me remove the administrative VLAN.


-Rainman

 

[Jsteve]

here is a qoute from a cisco doc that my clear this up.

"Enabling VTP pruning on a VTP server enables pruning for the entire management domain. VTP pruning takes effect several seconds after you enable it. By default, VLANs 2 through 1000 are pruning eligible. VTP pruning does not prune traffic from pruning-ineligible VLANs. VLAN 1 is always pruning ineligible; traffic from VLAN 1 cannot be pruned."

http://www.cisco.com/en/US/products...figuration_guide_chapter09186a0080160a7d.html

 

[Jsteve]

Vip maybe talking about clearing vlan 1 from a trunk, with the "switchport trunk allowed" command.

"You can remove VLAN 1. If you remove VLAN 1 from a trunk, the trunk interface continues to send and receive management traffic, for example, Cisco Discovery Protocol (CDP), VLAN Trunking Protocol (VTP), Port Aggregation Protocol (PAgP), and DTP in VLAN 1."

http://www.cisco.com/en/US/products..._guide_chapter09186a0080160a05.html#wp1020628