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Trunk Two cisco switches

Posted on 2013-10-25
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Last Modified: 2013-11-13
I have purchased a new switch (WS-C3750X-24P) to expand the port availability in my branch office. Existing switch (WS-C3750G-48PS) running IOS C3750-IPSERVICESK9-M and the new one comes with C3750E-UNIVERSALK9-M (IP base license).

What need to be done inorder to trunk new switch with existing one?.
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Question by:sumod_jacob
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by:Soulja
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At the very least one both switches

int typex/x
switchport trunk encasulation dot1q
switchport mode trunk
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by:Soulja
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other optional commands on the trunks are:

switchport trunk nonnegotiate    (disables DTP)
switchport trunk allowed vlan x-y   (restrict vlans on trunk)

other command available too, but the first post is the very least you need.
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by:Craig Beck
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...and either configure VTP if you use it, or manually create the VLANs on the new switch.
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by:Soulja
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On another note, if the switches are in the same rack, you may just want to stack them instead and treat them as a single switch. You will have to make sure they have the same ios version on them though.
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ampranti earned 500 total points
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Initially configure VTP :


conf t
   vtp domain domain-name
   vtp client
   exit


Check that vtp was updated:

show vtp domain
show vtp statistics


2. Then connect two ports using a cable.
Configure ports to both switches:


conf t
int g 0/24
switchport trunk encasulation dot1q
switchport mode trunk
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by:Soulja
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Two switches in a branch office....

VTP not needed.
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by:ampranti
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What need to be done inorder to trunk new switch with existing one?.

There is an old switch, probably using a VTP
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by:Craig Beck
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Maybe, but actually probably not.  There is only one switch there before the new one, so why would it be configured?

 If it's not configured I wouldn't recommend configuring it on the new switch as (a) many people see it as a security risk, (b) it won't accomplish the task.

Personally, I wouldn't configure it on a 2-switch stack anyway.
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by:ampranti
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Personally, I always configure a vtp plus a password (vtp password XXX) .
Even if there is only one switch!
When time comes to add a 2nd switch, its easy to distribute vlan info to the new switch in a few seconds.
I dont see why this could be a secuirty risk.


In addition, if there are no vlans, there is no need to configure a trunk port...
Just connect the switch! But then why you bought Cisco switches and not a layer-2 netgear prosafe ?

.....
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by:Craig Beck
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Yes, it may make VLAN distribution easier, but VTP is seen by many as a security risk and for good reason.  If it's configured badly it can break your network in seconds if someone adds a switch, or it could allow someone to learn and modify the VLAN configuration.  That is a security risk.

If you don't need VTP, or you only have one switch it's far safer to just set the VTP mode to transparent and never touch it again.
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by:Soulja
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Lol. This site never cease to amaze me.
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by:Craig Beck
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I know exactly what you mean Soulja! :-)
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