Query about WAN Link

[Mohamed Fyaz]

Hi,

I have trunked 3 vlans from layer 2 switch to Layer 3. In order for all this 3 vlans to have internet, may I know how I should link the layer 3 switch with router? Does that mean, one port I will allocate to the LAN port of the router and another port to the WAN port of the router.

Since I have 3 VLANS being trunked into a single port, how does this coorelation work between the trunk port and the remaining 2 uplinks (port for the LAN and port for the WAN in the same switch).

I do not if this makes sense, but please advise.

Thanks,
Fyaz

[Georg Pauwen]

Hello,

post the configuration of your Layer 3 switch and the router, so we can see what you have, and add the necessary bits and pieces...

[Mohamed Fyaz]

Hi Georg,

I have not done any configurations yet. this is a doubt which I was having. Lets say my layer 3 switch have a trunk port from layer 2 switch. How can I uplink this to the LAN port of the router? Can I just directly connect a cat6 cable from a empty port in the layer 3 switch to  the Router's LAN Port?

Please advise

Thanks,
Fyaz

[Georg Pauwen]

Hello.

indeed, a straight cable from switch to router will do. Assuming the layer 3 switch has SVI (VLAN) interfaces for your VLANs, the connection to the router will be a normal layer 3 to layer 3 link,where you just route the layer 3 networks.

[Mohamed Fyaz]

Thanks mate! 

Can you please give me an example of layer 3 to layer 3 router configuration?

Lets say my trunk port,from layer 2 switch fa0/24 is connected to layer 3 switch fa0/1. and I want to give the uplink to the router from layer 3 switch, from fa0/2 to router's gi0/0

So what route configuration i have to do from fa0/2 to g0/0.

please advise.

Thanks,
Fyaz

[Georg Pauwen · Accepted solution]

Hello,

here is a generic config:

Layer 3 Switch

interface FastEthernet0/2

description Link to Router

ip address 192.168.1.1 255.255.255.252

Router

interface GigabitEthernet0/0

description Link to Layer 3 Switch

ip address 192.168.1.2 255.255.255.252

You have to decide if you want to use a routing protocol or static routes between the Layer 3 switch and the router...

[Mohamed Fyaz]

Great thanks mate!! got it

So i will just route default routes to the next hop between the router and the switch. Guess this will work.

[Georg Pauwen · Accepted solution]

Hello,

on the router,  use the default route for routing traffic to the Internet, and more specific routes for your internal networks, e.g.:

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1 (interface towards the Internet)

ip route 192.168.10.0 0.0.0.255 192.168.1.1

ip route 192.168.20.0 0.0.0.255 192.168.1.1

ip route 192.168.30.0 0.0.0.255 192.168.1.1

The networks 192.168.10.0, 192.168.20.0, and 192.168.30.0 refer to the three VLANs on the inside.

[Mohamed Fyaz]

Thanks alot! This really helps mate :)