Native VLAN Help

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Oct 8th, 2008
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We are just about to start re-addressing our network and at the same time we're looking at breaking the network up into 6 VLAN's and stop using VLAN 1.


Currently on the edge switches we use VLAN 1, 2 (VOICE), 7 (Management) & 50 (Radiology) and originally we were just going to add switchport access vlan x to any ports that don't currently already have a VLAN assigned except for voice. This would mean a manual command entry for each interface.


I remember from a while ago that you can change the Native VLAN so it saves having to enter a command for every interface.


Which is the correct way of doing this manual input or changing the Native VLAN?


Thanks


Jon

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Jon Marshall Wed, 10/08/2008 - 03:40
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Jon


Could you just explain what you mean by changing the native vlan saves having to enter a command for every interface ?


Best practice from Cisco recommends having an unused, non-routed vlan for the native vlan.


Don't forget the "interface range .." command on most IOS switches can save a lot of typing.


Jon

jonhill Wed, 10/08/2008 - 03:54
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Jon


I thought that the native vlan command was a global command but after a bit more investigation it has to be entered into each interface so its no different than using switchport access vlan x.


Thanks


Jon

Marwan ALshawi Wed, 10/08/2008 - 03:41
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u only need to change the native vlan on the uplinks (trunk links)

with the command


switchport trunk native vlan [vlanID]


this vlan will be passed untaged throughout the network and be care that any mismatching of native vlan between two switches make unexpected problem make it the same on all ur switches better


if u have more than one trunk interface do the folloing


interface range fastethernet 0/1 - 5

switchport trunk native vlan [VLANID]


good luck

if helpful Rate

jonhill Wed, 10/08/2008 - 04:08
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If then that you change the native on the uplink and other interfaces are say on vlan 50 but the devices are are not sending tagged traffic will these interfaces get re tagged to the native vlan or willdo as they do now and just use vlan 50?


Thanks

Marwan ALshawi Wed, 10/08/2008 - 04:16
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native vlan usually used for managment and carring control traffic like bpdu,stp and so on

on the trunk the vlans passed with vlan taging except the native vlan passed untaged


for best practces do not assigne hosts to native vlan just use for managment for example telnet to the switch !!


hope this helpful

nick.franzen Wed, 10/08/2008 - 07:05
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Another best practice to be sure you are using is to make sure all unused ports are set to access mode and non-negotiate. Another step I take, is to create a local vlan that is not used. Then I assign non-used ports to that vlan and then dis-allow that vlan down any of my trunk ports.

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