Solved: Quick 3750/VLAN/IP Routing Question

jfraasch · ‎08-10-2009

I have a 3750 switch. Layer 3. I have all ports right now in VLAN 1. I need to point the PCs on this VLAN to an NTP Server that will be on a different subnet.

NTP server will plug into port 23.

There are probably two ways to do this.

First, I could add another VLAN interface like 1000 and put an IP on it then put port 23 in VLAN 1000. Then put a static route to the NTP server.

Or could I just put an IP address on the port and the PCs will see a route to it? Seems to me I am missing on step on this second solution.

Any third/better options?

James

Jon Marshall · ‎08-10-2009

James

With your first option you wouldn't need a static route as both vlan interfaces are on the same switch so they would be seen as directly connected.

Your first option is the way to go. Using routed ports on a L3 switch an ip address is used primarily for connection to other L3 devices not servers.

Jon

View solution in original post

Jon Marshall · ‎08-10-2009

James

With your first option you wouldn't need a static route as both vlan interfaces are on the same switch so they would be seen as directly connected.

Your first option is the way to go. Using routed ports on a L3 switch an ip address is used primarily for connection to other L3 devices not servers.

Jon

jfraasch · ‎08-10-2009

This is what I figured. A basic question.

Co-worker was adamant that he could just plug in the NTP server into a port in the same VLAN and configure a static route.

Wait, how are they going to even see that there is a route there? There is no other VLAN or layer 3 interface? It won't work I said.

Thanks for confirming I am not crazy.

James

Jon Marshall · ‎08-10-2009

James

You can plug the NTP server into a port in the same vlan as the other machines. But you still wouldn't need a static route.

When you configure NTP you configure the clients with the IP address/DNS name of the NTP server. If that IP address is on the same subnet the clients will be able to contact the NTP server. You don't need to add anything to the switch.

If you connected the NTP server into a port in a different vlan you would then configure L3 vlan interfaces for both the client vlan and the server vlan and set the default-gateway of the clients to be the L3 vlan interface of the client vlan, and the server default-gateway would be set to the L3 vlan interface of the server vlan.

Again, you wouldn't need a static route.

Jon

Joseph W. Doherty · ‎08-10-2009

If your 3750 is your only L3 device, what you would do is assign an IP address to each VLAN, have hosts on those VLANs use that IP address as their gateway address and enable IP routing on the 3750.