Solved: Connecting 4948s to 6509

rjrii · ‎01-07-2009

Hi guys, I plan to introduce two new switches into a production environment and would like to solicit your feedback to ensure I'm not overlooking anything. I must make the change without impacting current traffic and that's my reasons for approaching so cautiously.

First off, my environment currently consists of one 6509-E running 12.2(18)SXF10 which has been running fine up to this point with no issues. I plan to add two Cisco 4948 switches to my environment via ISL trunks running VTP.

Here's what I know:

I know I must set my 6509 as a VTP server (actually already set)

I know that I should ensure my new 4948s are configured as clients so that when they come online, my 6509 configured VLANs are not accidentally overwritten.

below is a show vtp status from my 6509

VTP Version : 2

Configuration Revision : 7

Maximum VLANs supported locally : 1005

Number of existing VLANs : 11

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : <REMOVED>

Configuration last modified by 127.0.0.51 at 11-7-07 16:33:29

Local updater ID is 127.0.0.61 on interface EO0/0 (first interface found)

Here is where my questions begin - prior to adding the 4948s, I assume I need to specify my VTP domain name on the 6509 (which will serve as the VTP server). When doing so, is there any risk to my current traffic? I would assume not, however, I believe specifying the domain name will automatically reset my config revision to 0? If that occurs, I think I should be safe as there will still be no other switches in the mix yet.

My next steps will include firing up the new 4948s (disconnected from the network at this point) and ensuring they are configured as VTP clients. Its my understanding that I can leave the VTP domain blank and that the 6509 will set the VTP domain during the first syncs over the trunk - please confirm? (The 4948s are brand new out of the box and will have a blank VTP Domain so I should not have to worry about some other domain existing, but I will verify that its blank before proceeding)

I plan to configure an ISL Trunk port on my 6509 that will then be connected to a trunk port on the first 4948 switch. I will then do the same from a second trunk port on the 6509 to my second 4948. Lastly, I'd like to trunk the two 4948's together for redundancy purposes should one of my trunk links from the 6509 to either switch go down, I still have connectivity to the core 6509.

I believe I have read the VTP specs and understand the process, but your feedback and experience with setting up similar environments would be greatly appreciated. Our environment is a 24/7 operations and I plan to do the work during our least busy time period, but at the same time, I want to be as careful as possible - you guys know the drill.

xcz504d1114 · ‎01-07-2009

You will need to set the VTP domain name on all clients and servers you want to participate in the same VTP domain, remember it is case sensitive.

Yes it will reset your VTP counter to 0, but this shouldn't matter since they will be the only switches in that domain.

VTP passwords also need to match if they are set, and make sure you are also running the same version of VTP.

Is the 6509 the ONLY switch on your network? If so then you are good with your order to connect, switch A, then switch B, then the redundant link, this should prevent any unwanted spanning-tree reconvergences.

I would suggest using dot1q for your trunk encapsulation as opposed to ISL though, functionally they do the same thing, but ISL is a cisco proprietary trunking protocol and dot1q is an industry standard, I would always opt for the non-proprietary one since you never know when budget constraints may impact your next upgrade / purchase, and it's better to be consistent with network designs.

Good luck, and let us know if you have any other conerns,

Craig

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xcz504d1114 · ‎01-07-2009