From Collapsed Backbone to Core-Router: Making a Cat 6500 Routing-only

Answered Question
Sep 27th, 2010

Hi there
We are on our way from a Collapsed-Backbone design to a real Core/Distribution/Access-Campus. Some of our Catalyst 6500 (Sup 720) will loose their Distribution-Layer-Function and work as Core-Router only. My question is: How do you configure a Catalyst 6500 as Router-Only; how far do you go / can you go with deleting the switching stuff:
- Is there a way to disable vtp alltogether? Or is setting them on vtp transparent the nearest thing?
- Can I get rid of Vlan 1 if I have no more switchports configured?
- If there are no more vlans and no more switchports - how can I get rid of my Spanning-Tree as well? Just removing all the statements from my config?
- Is there any other thing I can/should clean up if a Catalyst-Switch becomes a Core-Router?

Thanks in advance & Greetings from Berne
Stefan Mueller

(IOS is 12.2.18 SFX15a, Advanced IP Services K9)

I have this problem too.
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Correct Answer by Jon Marshall about 6 years 2 months ago

mullzkBern wrote:

Hi there
We are on our way from a Collapsed-Backbone design to a real Core/Distribution/Access-Campus. Some of our Catalyst 6500 (Sup 720) will loose their Distribution-Layer-Function and work as Core-Router only. My question is: How do you configure a Catalyst 6500 as Router-Only; how far do you go / can you go with deleting the switching stuff:
- Is there a way to disable vtp alltogether? Or is setting them on vtp transparent the nearest thing?
- Can I get rid of Vlan 1 if I have no more switchports configured?
- If there are no more vlans and no more switchports - how can I get rid of my Spanning-Tree as well? Just removing all the statements from my config?
- Is there any other thing I can/should clean up if a Catalyst-Switch becomes a Core-Router?

Thanks in advance & Greetings from Berne
Stefan Mueller

(IOS is 12.2.18 SFX15a, Advanced IP Services K9)

Stefan

VTP transparent would the be closest you can get.

You can remove the vlan 1 L3 interface and if there are no L2 switchports at all then none will be allocated into vlan but you can't actually get rid of vlan 1.

Yes, you can remove all STP from the config although personally i wouldn't. I would leave STP running for vlan 1. It won't harm you and you just never know if the wrong connection could be made or accidentally configured. Without any L2 loops there really is no impact on the switch.

Nothing much else as, if i understand correctly, all interfaces on all modules will be L3 routed ports only ie. not only L2 switchports but also no L3 vlan interfaces (SVIs).

Jon

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Correct Answer
Jon Marshall Mon, 09/27/2010 - 09:01

mullzkBern wrote:

Hi there
We are on our way from a Collapsed-Backbone design to a real Core/Distribution/Access-Campus. Some of our Catalyst 6500 (Sup 720) will loose their Distribution-Layer-Function and work as Core-Router only. My question is: How do you configure a Catalyst 6500 as Router-Only; how far do you go / can you go with deleting the switching stuff:
- Is there a way to disable vtp alltogether? Or is setting them on vtp transparent the nearest thing?
- Can I get rid of Vlan 1 if I have no more switchports configured?
- If there are no more vlans and no more switchports - how can I get rid of my Spanning-Tree as well? Just removing all the statements from my config?
- Is there any other thing I can/should clean up if a Catalyst-Switch becomes a Core-Router?

Thanks in advance & Greetings from Berne
Stefan Mueller

(IOS is 12.2.18 SFX15a, Advanced IP Services K9)

Stefan

VTP transparent would the be closest you can get.

You can remove the vlan 1 L3 interface and if there are no L2 switchports at all then none will be allocated into vlan but you can't actually get rid of vlan 1.

Yes, you can remove all STP from the config although personally i wouldn't. I would leave STP running for vlan 1. It won't harm you and you just never know if the wrong connection could be made or accidentally configured. Without any L2 loops there really is no impact on the switch.

Nothing much else as, if i understand correctly, all interfaces on all modules will be L3 routed ports only ie. not only L2 switchports but also no L3 vlan interfaces (SVIs).

Jon

mullzkBern_2 Mon, 09/27/2010 - 10:10

Thx a lot for this fast and complete answer.

- As Vlan 1 cannot be deleted, I'll definitly keep STP running ('downgrading' from MST to RSTP, though)

- Yes, we'll only have L3 routed ports on all modules.

Greetings from Berne,

Stefan

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