Cisco Switching from Layer 2 to Layer 3

Posted on 2013-10-28
Medium Priority
Last Modified: 2013-10-29
I'm new to layer 3 switching and want to see if I can get some help. Currently I have no vlans, and everything works. However I would like to do the below configuration and have vlan 10 and vlan 20 talk to each other. Can someone guide me on what I need to do on switch l2 (layer 2) and l3 (layer 3)? I'm assuming the layer 3 switch will do the routing, but I don't know how the uplink plays into the vlans and how to configure the Layer 3 switch. Switch L2 is a layer 2 switch and Switch L3 is a layer 3 switch. Can someone please help me understand how to configure this scenario?

Switch L2

Port 10 / - Client PC - vlan10 - I know how to make this a vlan
ip address:
subnet address:
gateway: 192.168.0.???? - What do I do here, put the internet gw

Port 20 / - Client PC - vlan20 - I know how to make this a vlan
ip address:
subnet address:
gateway: 192.168.0.???? - What do I do here, put the internet gw

Switch L3

Port 1 / - Internet - I don't know what to do here either.

1 Uplink from Switch L2 port 32 to Switch L3 port 33. - I don't know how to carry all the vlan traffic from switch l2 to the layer 3 switch.
Question by:jasonmohan
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LVL 18

Expert Comment

ID: 39607946
Ok, you would need to create 2 interface vlan on L3, one for each vlan

For example

conf t
interface vlan 10
ip address

interface vlan 20
ip address

These IP addresses will be a default gateway for your vlans respectively.

After you configured this, you need to configure a static route for internet connection.

Most probably it is going to be

ip route where X is your interner router/modem

What is your connection from L3 to Internet gateway?

Author Comment

ID: 39608455
I have a Cisco ASA at uplinked on port 1 of the Layer 3 switch, and port 1 on the Cisco ASA switch.

What do I need to do on the uplink port from layer 2 to layer 3 switch? I read some stuff regarding trunking but wasn't sure if I needed to add that, and how.
LVL 18

Accepted Solution

fgasimzade earned 2000 total points
ID: 39608476
You need to create vlans on both L2 and L3 switches and configure uplink ports between them in this manner:

conf t
interface fastethernet x/x
switchport trunk encap dot1q
switchport mode trunk

Then make sure you can ping interface VLANs' ip addresses from your PCs connected to L2 switch

When it comes to Internet, I would suggest configuring a new VLAN for communication between L3 and ASA

interface vlan 30
ip address

Then configure a port on L3 connected to ASA with vlan 30

Make sure you can ping from L3 to ASA

Dont forget about

ip route

Author Closing Comment

ID: 39608626
Thanks for the help, and taking the time to explain.

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