I'm new to networking and I'm a little confused so could do with some help.

I am currently using Cisco packet tracer and I am trying to configure a fictitious network. Initially I was just trying to get my network to function as intended, which I managed to do (except for getting both networks to be able to ping the same server) however now I am trying to edit what I have done to enter the details of the specifications I have been given and now I'm stuck.

My problem is as follows;

I have a Web server and DNS server with an IP address of for internet access. The internal LAN network is the Class C IP address: behind the firewall router provisioned with two Ethernet ports for the internal subnetted networks and one for the Web and DNS servers. I also need to think about security so the network also requires one sub-network for Admin and another for the Students.

Initially I configured one of my router port 1 to an address of with a subnet of to serve network 1 (lets call it the admin side).

Next I configured my second router port to an address of with a subnet of (which will serve my DNS server)

Then my third port with an address of with a subnet mask of and the forth with with a subnet mask of

Off my first port on the router as mentioned earlier I have my admin network and I have given one of the hosts an IP address of with a subnet of and a default gateway of and DNS server of

Off my second port on the router I have my DNS server. IP address- subnet default gateway - and of course the DNS server of itself.

Off the third port on my router I have my Web server with a IP address of and subnet of and default gateway of

Lastly I have my fourth port on my router serving the classroom side of the network with a and subnet of

Now when I change my DNS server and Web server to the IP address to it throws out the whole network, I have of course updated the dns server address and applied the new IP on the host computer etc but when I try to ping the server it fails. I'm not sure if its because the gateways IPs I have originally used are not meant to deal with this new IP?

The other question I have is that as mentioned above, I need to split the network, I have researched how to do this and I understand that I need to use a different subnet mask e.g but when I do this, it affects my DNS server since they have a subnet of so how can I get my DNS and web servers to serve both sides of the network? I can stop both sides (admin side and classroom side) from accessing each other fine but I cant figure out how to allow both networks access to the same DNS and Web server.

I have done lots of research to try and avoid asking for help hence how I initially got my network to work but since my question is so long I won't list everywhere. But I have looked for answers here and YouTube etc for clarity but after two days of looking and dealing with all these numbers as a beginner, I'm not having much luck! Any help or guidance would be appreciated.

closed as off-topic by Ron Maupin Jan 23 '17 at 14:21

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  • Do I understand you that you changed the IP addresses of your web server to 200.x.x.x on the router port configured with And the same with your nameserver? It sounds like you gave them the same IP address. – Ron Trunk Jan 19 '16 at 19:01
  • Respectfully, this question is way too long. Noone will read it all. Neither DNS nor Webservers are typically configured to serve a subset of subnets. DNS resolves names to ip addresses and Web servers respond to Web traffic. – Ron Royston Jul 26 '16 at 22:59

I think you are missing a key point to the networking... On a single network/subnet, all the devices must be on the same network/subnet. So, if you have port 1 as with a mask of, that means that all devices off that port must be in the IP range of (since you cannot use or and they all must have a mask of You cannot just change an IP address of a device on that network to something else, that will not work for many reasons. Same goes for Not sure if that is a typo, but nothing you mentioned would contain that IP address in the subnet.

You have two options that I can think of to get your desired result with the IP address.

  1. leave the IP addresses in the correct subnet for each port they are plugged into, then use NAT to forward based on the port (UDP53 for DNS and TCP80 and 443 for WWW) pointing to the appropriate servers.

  2. combine both roles (DNS and webhosting) into a single server, leave the IP address of, but make the port that it plugs into on that same subnet, possibly mask: Then you just have the clients access it based on that IP address.

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