Multiple VLAN 1

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Apr 12th, 2002
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Here is what I have.


1. I have a 3660 that has a FA link to a 5500. On that link, I have several sub-interfaces for my vlans; vlan 1, 10, 20 30, 50. the other switches (in the idf's) connect back to the 5500. I know I need to upgrade to a 4006, but that will come later. : )


Now.... I have another FA that connects to a 3524. On that FA, I have two sub-interfaces for vlans. what i need to do is provide two different vlans for my VOIP phones and phone switch. my question is this: the 3524 wants me to leave my native vlan as 1. this should be ok right? will this conflict with the other vlan 1 on the other interface or will the router strip that out of the packet anyway?


thoughts? make sense?

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m_nichols Fri, 04/12/2002 - 12:45
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was my message unclear? is any other information required?

Erick Bergquist Sat, 04/13/2002 - 00:12
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The router will strip the VLAN info off the tagged packet before it routes, so having the same VLAN # on multiple interfaces isn't going to break anything routing wise. The only problem you would run into is if both VLAN1's were part of the same IP subnet and you wanted to bring them both in the same router and route (can't do that because you can't multiple router interfaces in same IP subnet).


Why won't the 3524 let you change the native VLAN? Looks like this feature has always been there from the docs going back to 11.2(8). If you meant the router side then you need a newer release of IOS for the native keyword on the encaps command. If you don't have the native keyword, you can alternatively put the IP address, etc on the physical interface (not sub) and that will work as the native VLAN since the native VLAN in 802.1q is not tagged.


int fa0/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 20

switchport mode trunk


Hope this helps and was useful.


Erick

tmoreo Sat, 04/13/2002 - 07:40
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Are you trunking 802.1Q or ISL on the FA interfaces? Do you have a VTP domain? These are factors can determine, not whether they will conflict (because you can have many VLAN 1's on multiple devices) but instead whether they will be different or the same network. If you are trunking and all devices are in the same VTP domain VLAN 1 will be the same on both switches.

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