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Community Member

Native VLAN terms

Hi,

When configuring a Cat4006 with a separate layer 3 module installed, I'm confused over the term native LAN.

Q1.Some Cisco information mentions that VLAN1 is the native VLAN, is this correct?

Q2.Is the native VLAN where management traffic is sent over?

Q3.If so, what sort of 'management' traffic is using this VLAN?

Q4.Some information seems to state that the native LAN should NOT be used for user data, is this true?

Q5.If it is true, why?

Q6.If the answer to Q4 is yes, then what is the best way of configuring the trunks between the layer 2 and layer 3 modules to ensure that this segmentation is maintained?

For your information, the configuration requirement of a site is to connect ALL devices in the same VLAN (the Cat4006 is initially being used for layer 3 switching between multiple subnets on the same VLAN - to take the load off the external router).

I hope that there may be some person who can help me out of my state of confusion.

Thanks in anticipation.

regards,

Mark

3 REPLIES
Cisco Employee

Re: Native VLAN terms

Q1: yes - by default it is vlan1 but you can change it

Q2: yes

Q3: BPDU for spanning tree

Q4: correct

Q5: you don't want to drop management traffic because the vlan is overloaded with user traffic.

Q6: not sure what you mean - if you keep the default natvie vlan as vlan 1 and never assigned any user to it, when you create a trunk, you don't even have to ask you the question what about the native vlan.

Community Member

Re: Native VLAN terms

Gilles,

Thanks for taking the time and trouble to respond.

But I'm still confused. Cat4006/3524 etc, default with all ports in VLAN1, does this mean that only the uplink and downlink ports (ie. ports to other switches or external routers) should remain in VLAN1 (thus allowing management data such as BPDU to propogate via VLAN1 only) and all the user ports should be assigned a different VLAN eg. VLAN2?

Re: Native VLAN terms

Q1. Yes but this is just a default value and you can change it.

Q2. NO, native VLAN is set just on 802.1q trunk and has nothing to do with management. The confusing fact is that native VLAN and management VLAN have both the same default value = VLAN1.

Q3. Management traffic (Cluster Management Protocol, Telnet for CLI remote access, e.g.)is sent via management VLAN - another term. Unfortunately, some Cisco proprietary protocols (VTP, e.g.) are sent on VLAN1 without any possibility to change - even if you disable VLAN1 it is disabled for user data but still available for internal Cisco traffic.

Q4. It is better not to use management VLAN for user data to ensure bandwith for management traffic.

Q6. I don't understand the question.

HTH,

Milan

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