1

I currently have 3 VLANs. VLAN 1 is my default VLAN, and has on it a DHCP server, and my internet router.

I have set up VLAN 2 and VLAN 3, and my layer 3 switch has routing enabled and an IP for each VLAN.

The layer 3 switch is also set up with DHCP helper addresses, so that devices on VLAN 2 and 3 can both get IP addresses in the correct range from the DHCP server on VLAN 1.

All devices on all VLANs can ping each other, expect that devices on VLANs 2 and 3 are unable to ping the router on VLAN 1, or get any internet connection.

The Layer 3 switch has it’s default gateway at the router, and I hoped that this would be used as the next hop for accessing sites outside my LAN.

All of the devices on my network have the layer 3 switch as their default gateway, using the correct IP address for their specific VLAN.

So far, I have not done anything on the routing table of the layer 3 switch at all. It’s all on it’s default settings. I think I need a default route of some sort setting up, so that when people try to access the router, the Layer 3 can point them in the right direction.

However I’m not sure of the best way to do this. Can I set some sort of default rule that says that all internet traffic from all VLANs should look beyond the layer 3 switch, or do I need a specific rule for each VLAN to say where the internet traffic needs to go?

Any help would be greatly appreciated!

EDIT:

Here is my (sanitised) routing table.

IP Route Entries

Destination Gateway VLAN Type Sub-Type Metric Dist.

0.0.0.0/0 1.2.3.4 1 static 10 1
10.0.8.0/24 Zone-8 108 connected 1 0
10.0.1.0/24 DEFAULT_VLAN 1 connected 1 0
127.0.0.0/8 reject static 0 0
127.0.0.1/32 lo0 connected 1 0

4 Spice ups
2

I will double check my core switch as well when I get in the office, but I have a similar setup and I have

ip route 0.0.0.0 0.0.0.0 default gateway subnet

3

So assuming my default gateway is 1.2.3.4 on with the subnet mask of 255.255.255.0 I would need:

ip route 0.0.0.0 0.0.0.0 1.2.3.4/24

My routes table has the following headings on each of the default rows:

Destination | Gateway | VLAN | Type | Sub-type | Metric | Dist

The top row is currently:

0.0.0.0/0 | 1.2.3.4 | 1 | static | n/a | 10 | 1

Does that mean that I have the default route, but that it is currently only applying to VLAN 1, and not 2 and 3?

Thanks for your help!

@cweb

4

So I tried running the command:

ip route 0.0.0.0/0 1.2.3.4

However because there is already a line in the routing table with these addresses, it didn’t seem to do anything. The one that is there only seems to apply to vlan 1:

Destination | Gateway | VLAN | Type | Sub-type | Metric | Dist

0.0.0.0/0 | 1.2.3.4 | 1 | static | n/a | 10 | 1

I could try removing the line and then re-adding it, but I can’t do that right now as that route is being used.

I can’t seem to find the correct syntax for applying a route to specific VLANs, or a command to create a route for all VLANs…

5

Have you set up inter-VLAN routing? 802.1Q encapsulation with subinterfaces set for each VLAN on the connection from your layer 3 switch to the default gateway I think will solve your problem.

6

Yes, inter VLAN working was fine for everything apart from the internet connection.

I’ve just solved this - my setup was fine, but the internet router (which I am unable to configure) was only aware of my original VLAN so was unable to send the traffic back. It’s been resolved by my ISP modifying this rule.

7

I’ve just solved this - my setup was fine, but the internet router (which I am unable to configure) was only aware of my original VLAN so was unable to send the traffic back. It’s been resolved by my ISP modifying this rule.