VLAN configuration question

Unanswered Question
Feb 28th, 2008

I currently have two seprate switches connected via separate Fas interfaces to the same router. I am planning to replace the current router with a new 3800 router and use the same Gig interface to connecet both separate switches (segments) by creating interVLANs. The current production router is configured as follows:

Fas 0/1 IP: 10.10.51.1

SW1: VLAN 1: 10.10.51.2

Default Gateway: 10.10.51.1

Fas 3/0 IP: 10.17.54.1

SW1: VLAN 1: 10.10.54.2

SW2: VLAN 1: 10.10.54.3

SW1: VLAN 1: 10.10.54.4

SW1: VLAN 1: 10.10.54.5

Default Gateway: 10.17.54.1

So, my plan is to configure the new router with one of the Gig interfaces with the following:

Gig 0/1.51

'dot1q encapsulation

IP address: 10.10.51.1

Gig 0/1.54

'dot1q encapsulation

IP address: 10.10.54.1

SW1: VLAN 1: 10.10.51.2

'dot1q encapsulation

Defafult Gateway:?

SW2: VLAN 1: 10.10.54.2

Default Gateway: ?

I currently have two seprate switches connected via separate Fas interfaces to the same router. I am planning to replace the current router with a new 3800 router and use the same Gig interface to connecet both separate switches (segments) by creating interVLANs. The current production router is configured as follows:

Fas 0/1 IP: 10.10.51.1

SWS1: VLAN 1: 10.10.51.2

Default Gateway: 10.10.51.1

Fas 3/0 IP: 10.17.54.1

SWK1: VLAN 1: 10.10.54.2

SWK2: VLAN 1: 10.10.54.3

SWK1: VLAN 1: 10.10.54.4

SWK1: VLAN 1: 10.10.54.5

Default Gateway: 10.17.54.1

So, my plan is to configure the new router with one of the Gig interfaces with the following:

Router:

Gig 0/1.51

'dot1q encapsulation

IP address: 10.10.51.1

Gig 0/1.54

'dot1q encapsulation

IP address: 10.10.54.1

Switches:

SWS1: VLAN 1: 10.10.54.2

SWK2: VLAN 1: 10.10.54.3

SWK1: VLAN 1: 10.10.54.4

SWK1: VLAN 1: 10.10.54.5

'dot1q encapsulation

Defafult Gateway:?

SWK2: VLAN 1: 10.10.51.2

Default Gateway: ?

My questions are:

1- Do I need to create a native VLAN on the router? If so, what should the default gateway ip addresses to be assigned to the switches?

Thanks,

sK

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darwintobardelgado Thu, 02/28/2008 - 14:20

Hi sK,

You don't have to create the native vlan. The native vlan transports control information like CDP, VTP, etc.

You need to configure in the router what is the native vlan. For do it, you can use the command:

encapsulation dot1q [X] native, in the interface configuration mode, where X is the native vlan ID. You don't need to configure any gateway for the native vlan.

The gateways for all other vlans should be the ip address for each router subinterface.

Best regards,

DT.

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