Switches - Cisco 2960X

Network Diagram

Take a look at the attached diagram to see what I'm trying to accomplish; I think it should be pretty self-explanatory.

Switch 2 and Switch 3 I would make sure both VLAN1 and VLAN2 exist. The DHCP server on the 172 subnet would need to provide the IP address for the computer network off Switch 2.

Where would I need to create the IP helpers? Switch 1, 2, and 3?

My other concern is the WAN. VLAN1 will use address and VLAN2 will use Both go over a single Ethernet cable from WAN to Switch 1. Will that work since I have separate VLANs or should I connect WAN to Switch 1 using two Ethernet cables -- one to VLAN1 and one to VLAN2?

Any thoughts or advice?



  • Welcome to NE, we hope you will both contribute to and learn from this community. You could improve your question by editing it to add more details. You may find our Question Checklist helpful when editing your question. For example: with which device are you doing your L3 routing, what device is doing NAT, etc. – YLearn Jul 7 '15 at 3:12
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    In your diagram, since you are running a DHCP server on both VLANs, you don't need an IP helper statement anywhere. If you only had one server, you would need the statement on the L3 interface serving as the gateway for the VLAN that didn't have the DHCP server. The WAN/NAT question you should probably split off into a separate question of it's own as they are really two different topics. – YLearn Jul 7 '15 at 3:15
  • @YLearn okay that makes sense since the DHCP servers are on their own VLAN. For Switch 2, do I need to create a VLAN2 still since all ports on Switch 2 will be for VLAN2? – Michael Jul 7 '15 at 3:38
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    Does "Trunk" on the lines between the switches indicate VLAN tagging? If so then all three switches should be aware of all VLANs that will be used. You can manually create matching VLANs on each switch or use VTP to replicate a VLAN database among them. – Todd Wilcox Jul 7 '15 at 13:01
  • @ToddWilcox Yes that's correct trunk indicates VLAN tagging. I've realized maybe I don't need the trunk line from Switch1 to Switch2 because no one on Switch2 will be on VLAN1. Instead, I will just connect Switch1 to Switch2 over one of the VLAN2 ports on Switch1. – Michael Jul 7 '15 at 16:47

You got it. The diagram looks right as is. No ip-helper address required.

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