Switch-on-a-stick.

[ciscogeruta]

I am looking for a solution to setup what essentially is the L3 switch version of a router on a stick.

I have an ESXi server connected to a 3550 and im looking to do intervlan routing between vlans that exist on a trunk between the esxi server and the 3550 switch.

Earlier today I was successfully about to setup intervlan routing by using a router and using sub interfaces.

With my attempt to use a L3 switch, I see that you cant create sub-interfaces and I cant quiet understand how to properly setup the switch.

Attached is a picture of what i am trying to do.

Again, this works using a router instead of the L3 switch and using sub interfaces, but i need to know how to do this for a l3 switch.

Thanks.

[Richard Burts]

On a layer 3 switch with routing enabled it is quite simple and straightforward to do what you are asking about. You would configure it something like this assuming that vlan 10, vlan 20, and trunking are correctly configured

interface vlan 10

ip address 172.16.10.0 255.255.255.0

interface vlan 20

ip address 172.16.20.0 255.255.255.0

This would allow both vlans on the trunk and would enable routing between the vlans. There is no need for subinterfaces or anything like that if you are doing the inter vlan routing on the layer 3 switch.

HTH

Rick

[Reza Sharifi · Accepted solution]

You can do the same functionality on the switch but instead of using sub-interfaces you use SVIs.

So for each vlan you create an SVI and give each SVI and IP address:

Example for vlan 10 and 20

config t

inter vlan 10

ip address 10.10.10.1 255.255.255.0

no sh

inter vlan 20

ip address 10.10.20.1 255.255.255.0

no sh

I am assuming your 3550 supports configuring multiple SVIs and inter-vlan routing.

config t

ip routing

HTH

[ciscogeruta]

I will have to enable ip routing because its not by default.

But i have a few questions concerning what you wrote above.

1. Do i setup the fa0/24 port as a trunk port?

2. Do i need to map an SVI to a trunk port?

3. Will the SVIs be down since theres no access ports mapped to them?

4. Will i need to create manual routes or will the switch build them automatically because they are connected?

Thanks.

[Reza Sharifi]

1. Do i setup the fa0/24 port as a trunk port?

Correct since you have multiple vlans traversing fa0/24 you need to trunk the interface and add vlans 10 and 20 to it.

2. Do i need to map an SVI to a trunk port?

No, you just configure the layer-2 and layer-3 (svi) for each vlan and make sure to do a "no sh" for each

3. Will the SVIs be down since theres no access ports mapped to them?

no, as long as the vlans exist on the trunk the SVIs should be up.

4. Will i need to create manual routes or will the switch build them automatically because they are connected?

No need for manual routes installation.  Both vlans will be connected interfaces and when you turn on ip routing the vlans should communicate with each other.

You also need to configure the vlans on the ESXi host.

HTH