Problem with VLANs

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Re: Problem with VLANs

by albertodegama » Mon Mar 26, 2012 1:57 am

Hi All,

I've got a weird little problem. I've got about 50 switches (2950's,
3500's, 4006's) and about 40 different vlans which make up my network.
We have close to 1100 PC's on the network, we have segregated vlans
based on geographic location within the building.

The problem we are having is in some cases when we move PC's or replace
PC's, the PC is unable to pick up an ipaddress on a specific VLAN (ie a
PC is on VLAN 37 is moved to a new location and the port is configured
to VLAN 37 but it is unable to obtain an IP address or a PC is replaced
with a brand new one but it still is not able to obtain an IP)

The problem isn't DHCP related, as these devices are unable to
communicate with anything even when configured with a static IP.

Now the strange part, if I change the vlan that the port is configured
to use, the device will start working ie going from vlan37 to vlan446.
Also if after a couple of days/weeks I set the port back to the orignal
vlan it will work again..

This problem has only reared its ugly head in the last 6 months. It is
becoming more frequent. Can anyone suggest where I start looking to
try and resolve this problem?


Thanks in advance

Re: Problem with VLANs

by agagagugu » Sat Apr 30, 2011 7:26 am

I can not see any diagram or configuration

Re:Problem with VLANs

by Guest » Sun Jan 02, 2011 11:40 am


Hi Tigin Its great it solved ur problem

Re:Problem with VLANs

by Guest » Sun Jan 02, 2011 11:26 am


Thank you all very much for your help, the problem was solved by forcing the SFP ports into trunking mode.

Re:Problem with VLANs

by Guest » Sun Jan 02, 2011 11:21 am


Hi TiginMeery Christmas,Looking at your scenario I would recommend you to make following things1) Create a VTP domain (name it any thing for eg cisco)2) Then make 3560 G switch VTP mode server and domain cisco3) Other tow switches will be VTP mode client and domain cisco.4) use this command switch port trunk for the gigabit interfaces connecting 3560 and 2950 from 3560 switch.Make sure you have the same encapsulation in all swicthes and VTP version to remains same.Do this and if u need any further assistance contact me.CheersYasir

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