Voice VLAN addition to router sub interface? what is the default gateway on L2 switches behind the router?

[vasanth77]

HI,

   I'm running native vlan(data) currently with default settings in L2 switches and I want to add Voice vlan with the same interface as sub interface ip for data and voice,

example,

Vlan 1-data---IP 10.0.1.0/24-->on fa 0/0.1 of router sub interface

Vlan 5-Voice--IP 10.0.5.0/24-->on fa 0/0.5 of router  sub interface

My L2 ,29xx series switches already configured with the default gateway 10.0.1.1 previously,

If I add a voice Vlan in L2 and also router sub interface,

then what IP will be my default gateway?

How could I add route for that?

[Mark Malone]

ip stays the same  , Just point it at the vlan 1 the router will take of DF for the phones.

Just make sure whatevers giving out DHCP for the phones it is set as correct gateway 10.0.5.1 or else youll have issues

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/336-cisco-router-8021q-router-stick.html

[vasanth77]

Hi Mark,

Really helpful,nice presentation.

thanks a lot.

R1(config-subif)# encapsulation dot1q 1 native

what is the need to mention Native in the above command,Vlan 1 is the default  and Native,

If I'm using Vlan 5 as a data VLAN,then can i use the Native command over 

i.e(R1(config-subif)# encapsulation dot1q 5 native

SW1(config)# interface vlan2
SW1(config-if)# description Voice Vlan
SW1(config-if)# ip address 192.168.2.2 255.255.255.0
SW1(config-if)# exit

is it Necessary  to assign IP address for Voice vlan 2 in switch,because we already assigned IP for Vlan 1(DATA),If I'm not assign IP for Voice VLAN what will happen?

What is the purpose of IP NAT INSIDE command in Sub interface?

[Mark Malone]

Hey

1 yes leave vlan 1 as native as that's the default unless you require to change it

2 No only have 1 native vlan its for untagged traffic , you would never have 2 natives it will cause issues

3 Only 1 ip address required on the layer 2 switch vlan 1 is fine and its only purpose is only for reachability and management so no int vlan 2 required at all , vlan 2 just needs to exist at layer 2 as you already gave it a gateway on your sub-interface for its traffic and the router will take care of the rest

4 The nat is so devices can speak to the internet very important without that they can only speak to each other locall7y

[vasanth77]

Hi Mark,

thank you