Outside switch restriction

Unanswered Question
Jun 2nd, 2009
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Dear All,


I would like to restrict outside Switches connecting to our network. its noticed that employees brings 8 port switches to work place and connecting to their lan port. from their they are extending to personal laptopes e.t.c


Heard that connecting High revision switches into network will washout entire vlan configuration of existing network.


How to restrict outside switches connecting to our network?


Thanks



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John Blakley Tue, 06/02/2009 - 05:48
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If your edge switches are Cisco, you can use bpduguard with portfast enabled on the ports that you want to protect. When the switch senses a bpdu on that port, the port will shut in an err-disabled state. You can have the port automatically reenable after it stops hearing bpdus by using:


"errdisable recovery cause bpduguard"

"errdisable recovery interval "


HTH,

John


Edison Ortiz Tue, 06/02/2009 - 05:50
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The configuration of bpduguard on access-ports may alleviate the problem if the switches send bpdus.


As we know, most SOHO switches do not use bpdus so you are left with implementing port-security on the access-ports.


As to how many MAC-Addresses are allowed on each of the switchports, the answer is; it depends. If you have VoIP, then you need 2 MACs in the access-vlan and 1 MAC in the voice-vlan. If you don't have VoIP, then you can configure each switchport for 1 MAC.


HTH,


__


Edison.

Joseph W. Doherty Tue, 06/02/2009 - 09:24
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"Heard that connecting High revision switches into network will washout entire vlan configuration of existing network. "


That's possible if it's a Cisco switch with VTP. There are VTP options to minimize or negate this risk, especially in the later VTP features.


"How to restrict outside switches connecting to our network? "


Difficult to do unless you're using some of the latest Cisco switches and access port authentication. Not positive, but I recall some switches might support a simple method to limit number of MACs allowed active on an access port. However, NAT type devices can hide number of devices behind single MAC.

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