effect of no VTP server switch (all switches in VPT Client)

boss

Hi guys. I have a problem where if an IP device is plugged into a network, it resets network connections. I have VoIP on the lan, so PC connect via IP phones. So the IP phone shows the 'Configuring IP' on the display. The are two switches on the site with 2 vlans, 1 is voice and the other is data. I discovered that both switches are in VPT client mode (and No server). Could this be the cause? I suspect STP is being forced to converge somehow.

Any help?

Mr.Ping

In my opinion it is highly unlikely that VTP client configuration is the cause of your problem.
What VTP client configuration does is make it impossible to create vlans locally on the switch.
This means a VTP client will only receive VLAN configurations from the VTP server.

What device is being plugged in to the network and why do you suspect that it causes STP reconvergence?

boss

If a phone is plugged in or PC, this seems to rest things. Therefore I thought it could be STP being forced to converge.

mikearama

Clients don't force convergence... servers do.

But, to rule STP out, why not switch the devices to Transparent. Then, if the condition continues, you can rest assured that STP isn't the culprit.

boss

Thanks will try that and come back.

Netstudent

What is the correlation between VTP and STP? How could VTP modes affect STP convergence? I just can't find the common denominator here.

Boss, could it be that the reason both switches are configured as clients is because someone doesn't want the VLANs to change? Are the switches even part of the same VTP domain?

mikearama

Wow NS... good eye. Boss started out talking about vtp, and in his final question asked about stp... and I just fell into the same pattern.

So where I typed STP in my post, please read: VTP

Netstudent

oh ok cool.

boss

Ok gentleman, maybe I confused you somehow. Let me state the question as this:

You plug in a new device on the network and the network pc (and IP Phone) connections reset. There are 2 vlans on switch, one for voice, one for data.

In diagnosing prblem I discovered that both switches were vtp clients with blank domain and wondered if this had anything to do with this or the problem lies elsewhere.

I just cant positively think of the cause here? Your ideas gentlemen are appreciated.

Thanks

Netstudent

So when you plug the ip phone into the switch the whole switched network drops?

I'm not quite sure what you mean by "reset". If the VTP domain is null, then I doubt this is a VTP problem.

dtlokee

The first thing that comes to mind is spanning tree. I am thinking the addition of the device is casuing a TCN to be sent causing STP to reset. Are you using RSTP? I would consider using portfast and bpduguard on the edge devices to stop them from generating a TCN when the link becomes active.

Aquabat [banned]

dtlokee wrote:

The first thing that comes to mind is spanning tree. I am thinking the addition of the device is casuing a TCN to be sent causing STP to reset. Are you using RSTP? I would consider using portfast and bpduguard on the edge devices to stop them from generating a TCN when the link becomes active.

the master has spoken.

boss

Ladies & Gentlemen, I think I have discovered the problem here. I have just been analysing the configs for the two switches. Physically, Switch1 must be connected to Branch router and it also conn to Switch2. Going thru Sw1, there are 2Gi ports forming an EthChannel. 'sh int status' shows that both Gi ports are connected. If a go to Switch2, there is 1Gi port configured in an EthChannel and 'sh int status' shows only 1 Gi port connected. ===> so I suspect someone connected one of the Gi ports (for EthChnl) on Sw1 to the Branch Router and the other to Sw2. So the 2 Gi's on Po (Sw1) are not physically connecting to same device. Router has a Gi whose status is up to Sw1. ***THIS SHOULD BE THE PROBLEM. WHAT DO YOU THINK??? ***To answer one of you guys, I'm using portfast on switch.

dtlokee

Yeah that would be a mess if that was what is going on, but I suspect there isn't really an etherchannel there, what does the output of "show etherchannel summary" display? If it was forming an etherchannel I would think you would have all kinds of connectivity issues.

boss

Just an UPDATE.......the problem wasnt the Etherchannel as they were not bundled. Corrected config and problem persisted. Isolated problem to Sw1. The connection resets were happening when Sw1 was plugged with something, but plugging into Sw2 would not reset connections. Replaced Sw1....Thakns for taking you time with this!!!!!