First time posting a question here, please bear with me.

I've been assigned to manage the migration of all our computers and servers from a facility where we have 2 ISP's to a facility where we're going to have only 1 ISP.

  • Currently we got one ISP for the office area and the other ISP is for the production.
  • Both networks have access to a single NAS for shared files and contain 3 switches (Cisco Catalyst 2960G) in total
  • The production area uses static IP's (5 static IPs) where as the offices use DHCP.

The new building we're moving into is going to have only 1 ISP Verizon with 5 static IP's where an ethernet cable going to a switch for distribution.

I'm a programmer and have knowledge on some basics about networking, but I've never done something on this big of a scale.

My question is how can I use the existing switches to assign the fixed IP's to certain servers and production PC's and leave the rest for DHCP like for hard wiring WiFi's and office PC's, printer's, smart TV's etc.?

  • 2
    I suggest hiring a networking expert. – Tommiie Sep 19 '18 at 16:27
  • I have to agree with @Tom. I suspect I get the gist of what you're asking, but your question isn't the clearest, and I suspect this is because (as you've mentioned) you're a programmer, not a network engineer. Which might also make it difficult for you to implement any technical recommendations you get as answers. – Matt Sep 19 '18 at 20:35

It's a broad question but let me see if I can help you a bit. Your ISP provides you with public address that you use to go out to the Internet. So if you are no staying with one of your ISPs and getting a new one there's a few changes you will have to make. For the servers (Production) you have to reconfigure the switch where you connect your servers and the IP addresses since you assign them manually. For the office you would have to change the routing interface configuration on the layer 3 switch (I guess) and conserve the DHCP configuration because it's a private LAN. If that doesn't clarify your question, please provide more details to narrow down the scenario or feel free to ask more questions.


Tom has the gist of it. This is going to be a huge mess for you without networking or Cisco IOS experience. That being said, here's an attempt at an answer:

I'm going to assume that all the IPs you're talking about are internal rather than the public IPs provided on the ISP WAN. With luck for simplicity, you have everything on a single Class C subnet (netmask of AKA CIDR /24).

You have DHCP server already I assume, you'll need to carve up the DHCP server by either shrinking the range it services to only cover some of the subnet (e.g. from x.x.x.2 to x.x.x.127) and use the rest manually OR cover the whole range and create exceptions inside of the range (e.g. x.x.x.3 is blocked from being given out by DHCP). Once you've done this, the servers can be statically assigned to the IPs you want without fear that another machine will get assigned the same IP.

Alternatively, you can set the 'static' IPs in DHCP with reservations. That means they'll always get the same IP from DHCP every time. This is a bit more dangerous, especially if they are Active Directory servers, exchange servers, etc.

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