2 Cisco CCNPs were on Campus Yesterday (with salespeople)

deneb829

We are looking to upgrade our network switches. We are on a campus environment. Both CCNPs (one of which was a beautiful woman and the other looked and sounded like that guy from Slingblade - both were knowledgable and nice) told us that we were pushing the limits of the switches by having around 45 VLANs on campus (2 for each building).

I wasn't really clear on what the problem was, and didn't have time after the meeting to get clarification. A search on the web turned up errors that switches get from too many vlans, but I am interested in what the specific cause is.

I wasn't sure exactly where to post this, but since it was 2 CCNPs, I figured here would be ok.

keenon

was this at the core causing the issue? what was the error message and what types of switches are u using? i'm going to digress as i had a slew of questions that just came to mind

deneb829

keenon wrote:

was this at the core causing the issue? what was the error message and what types of switches are u using? i'm going to digress as i had a slew of questions that just came to mind

As far as we know, we don't have any issues related to the vlans. The CCNPs told us that too many vlans cause spanning tree issues - They said that 64 is the maxium number of vlans that can be trunked. I know what spanning tree and trunking is and how it works, I just don't see the connection.

keenon

where is the stp root for each vlan? what type/model device do you have at the core of the network ?

Humper

keenon wrote:

where is the stp root for each vlan? what type/model device do you have at the core of the network ?

I think there core switch is a Cisco 2900 series

wildfire

I wasn't sure exactly where to post this, but since it was 2 CCNPs, I figured here would be ok.

Just because the yield the Title CCNP does not make them carte blanche experts, it means they can pass the exams.

the number of Vlans really does depend on the type of switches used

For example I look after a network with 100's of vlans on the 6500's

but a lonsesome 3550 may not be up to the task. After all why limit the vlans to the 40s when they support nearly 1000 by default and I think (dont quote me on this) 4096 max.



Problems can occur especially if you have PVSTP (per vlan STP) as each Vlan has it own proccess. Trunking can become a bandwidth issue also, but again dependant on model and link speed.

Humper

I agree with wildfire.....Heres an example - There was a CCIE a coworker met once and said that when they put a switch onto a layer 2 network and put the switch on the same VTP domain that VTP will merge the two databases together, as you know this is not the case.

NetworkGod

you should've asked that CCNP woman out, i would

PCHoldmann

Without a better understanding of you network, I am making some assumptions from your post, and can’t say for sure what the best solution would be, but it sounds like a case of "just because you could doesn’t mean you should.” Cisco seems to be getting away from the larger VLANs that span a campus, leaning more towards using multi-layer switching, and dividing layer 2 networks between buildings. From your post it sounds like you have around 20 buildings, with everything trunked between them. This would constitute a large waste of bandwidth in the core as broadcasts are propagated throughout the campus, as well as increased spanning tree convergence time, and possible sub-optimal paths from STP. It may be better in this case to make the VLANs local to the building, and use layer 3 routing to connect the building to the rest of the campus. This would allow better use of resources, load balancing, etc. Within this environment, you would not have more than a few VLANs in any given area (and STP domain), the VLANs end at the layer 3 boundaries of the buildings. Again, 30,000 ft view, not knowing the exact details.

Peter

cisco_trouble

yeah i agree, too little info. But having a 2900 router as a core, will cause problems. Its more like a flat network than anything with all the processing the router has to do...

deneb829

PCHoldmann wrote:

From your post it sounds like you have around 20 buildings, with everything trunked between them. This would constitute a large waste of bandwidth in the core as broadcasts are propagated throughout the campus, as well as increased spanning tree convergence time, and possible sub-optimal paths from STP. It may be better in this case to make the VLANs local to the building, and use layer 3 routing to connect the building to the rest of the campus.
Peter

What you are saying here makes alot of sense. We have over 20 buildings on campus. I consider my knowledge of switching and routing to be 'working', but nothing in depth enough to know exactly what was the issue. Sorry that I wasn't more clear - it's not my network, but I am involved with some of the network planning (I work with the network administrator, but only based on my experience and that I ask to be involved - it's not the position for which I was hired). I don't know the exact number and models of switches. I have the exact numbers and models at the office and we are on fall break for the next 2 days. I do know that we have several 3500 series switches ranging from 3500's to a few 3560's. Our core router runs on 6509 blades - for it we're going to be upgrading the management blades.
Thanks - I think you answered my question.

n3tw0rkg0d wrote:

you should've asked that CCNP woman out, i would

Being happily married and having a child on the way might be a problem here (at least it would be for me). Maybe under different circumstances, still I might be a bit intimated.
I think it would go something like this ...
Act 2 Scene 6 from "The Tech Exams Bar"
Me: "Hey baby, want to come see my network?"
Hot CCNP: "What are your certs?"
Me: "Working on my MCSA - I've passed 70-290, and" voice trailing "I have my A+"
Hot CCNP: "Microsoft." Said flatly "No thanks. Why don't you go find yourself a nice MCP?"
Me: "Have you seen those women?"
Hot CCNP: "Yeah, I have." To which she walks away into a group of CCNPs and CCIEs. I look over longingly - they look like rock stars to me. With a sigh, I turn and walk back to my own group. There aren't even any women over there.
MCP Geek: "Hey! Mike's back. Hey Mike come over here and sit with us, we're talking about why Windows XP is better than Linux!"
Me: "Uh, sure guys ... I'll be there in a few minutes." I finish my drink and slip out the side door. "Man, those Cisco guys are so much cooler," I think to myself. "Heck, you even need an 850 to pass their exams!" At least home has the latest Playboy issue "Babes of Cisco". You won't see a babes of Microsoft ... we at least not in Playboy. Man ... I've got to get Cisco certified.

Humper

lol thats funny!

keenon

PCHoldmann