Cisco 2921 VLAN configuration

[umeshunited]

We have one vlan configured on cisco 2921 router , VLAN 50.  There are five interfaces on VLAN50 (IP on this vlan is Gateway) . Fa0/2 to Fa0/6. Now I want to move one of the server that is connected to Fa0/6 to Nexus switch.

So after we move it to nexus. It will be like Server > Nexus > 2921 . I am planning to configure one free Gig port available on 2921 to use between Nexus > 2921 connectivity. If I create one gig subinterface (gi0/1.1) and put " encapsulation dot1q  50 " on that. Will it work ?

[paul driver]

Hello

it Is feasible but you can also leave that interface as it is and create a l3 svi on the nx-os and assign the access ports on the switch to be in vlan 5 and relocate all you hosts thus freeing up the router ports

It all depends what your future plans are for the switch - if I had the choice I would make the switch a L3 switch for future inter-vlan routing.

[umeshunited]

Hey Paul, 

Thank you for reply,

As of now client requirement is such that they do not want to create SVI on switch , it is going to be on router only.

So Config on gi0/1 of 2921 will  be.

inter gi 0/1

no shut

inter gi 0/1.1

encapsulation dot1q 50

Do I need to make it native ?

[Georg Pauwen]

Hello,

if you already have Vlan 50 with an IP address, and all you need is extend Vlan 50 to the Nexus, you only need to make both ports on the 2921 and the Nexus access ports in Vlan 50...

[umeshunited]

Thank you for reply George,

The reason I was confused is that on 2921 currently VLAN50 with IP is configured and some other FE ports in vlan 50.

If I swing one of the server off Gigabit interface via Nexus , will I be able to configure vlan on that gig interface.

Config on gi0/1 of 2921 will  be.

inter gi 0/1

no shut

inter gi 0/1.1

encapsulation dot1q 50.

Do I need to make it native ?

[paul driver]

Hello

rtr

inter gi 0/1
no shut

inter gi 0/1.1

encapsulation dot1q 50
ip address 50.50.50.1 255.255.255.1

nexus
conf t

vlan 50
exit

int x/x
description link to router
switchport mode trunk

int x/x
description link to server
switchport mode access
switchport access vlan 50

[Richard Burts]

I believe that we need to have better understanding of the original environment. If I am reading the original post correctly then vlan 50 already exists on the router and ports on the router already belong to vlan 50 and that there is an active gateway on the router for vlan 50. If that is the case then I do not see how it would work to try to put an IP address on G0/1 or on its sub interface that is in the same subnet.

Also I am thinking about this statement in the original post:

one of the server that is connected to Fa0/6 to Nexus switch.

If the server is moving from a connection on the router to a connection on the Nexus then why not use Fa0/6 to connect to the Nexus (in vlan 50)?

HTH

Rick

[umeshunited]

Hi Rick,

Good day!

The reason we do not want to use Fa0/6 port is that, we are changing hardware, server will now reside in new hardware.

Considering future expansion we want to use Gig interface instead of Fa0/6 interface. 

[umeshunited]

Hi Rick,

Good day!

The reason we do not want to use Fa0/6 port is that, we are changing hardware, server will now reside in new hardware.

Considering future expansion we want to use Gig interface instead of Fa0/6 interface. 

[Richard Burts]

Thank you for the clarification. I can understand the desire to have a Gig port for the new server hardware. However moving one server from the router to Nexus while leaving other devices connected in vlan 50 on the router does create a problem. You describe what you want like this

It will be like Server > Nexus > 2921

So the question becomes what kind of connection will it be between Nexus and 2921? You are suggestion that the Nexus would be a layer 2 interface (might be an access port, probably would make more sense as a trunk) and to configure a sub interface on 2921. The problem is that putting an IP address in vlan 50 on the Gig sub interface would conflict with the IP address in vlan 50 that you already have on the router. 

I can see a couple of possible solutions for this.

1) When you implement the new server hardware would it be possible to create a new vlan on the Nexus, give the new server hardware an IP in the subnet of the new vlan, and configure the sub interface on the router for that new subnet?

2) You could move all of the devices currently in vlan 50 on the router to the Nexus. This would free up router ports, and it would allow you to remove the existing vlan 50 and its interface vlan 50 from the router and create the sub interface on the router to be the gateway for vlan 50.

3) This may see a bit odd but I think in some ways it would be the best solution. You could create vlan 50 on the Nexus, put the new server hardware on a Gig port in vlan 50, connect fa0/6 which was freed up when you took off the existing server to a port on the Nexus in vlan 50. Leave vlan 50 on the router with the other currently connected devices, (here is the interesting part) then remove interface vlan 50 and its IP address from the router. Make the connection from Nexus to 2921 a trunk port carrying vlan 50 (and potentially other vlans), and configure the sub interface for vlan 50 on the router as the gateway for vlan 50. Essentially what you are doing is to move the vlan 50 gateway from interface vlan 50 to the sub interface on the Gig interface.

HTH

Rick

[umeshunited]

We are going ahead with Gig card in stead of FE in 2921. Will update soon.