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  • Changing network ip addres - HELP!

    Guys,

    New work and first new project.

    I have to change my whole company production network ip address scheme. Currently all address start with 192.168.0.x.

    We would like to change those to something else, maybe like 172.x.x.x or whatever as long as they donít start with 192.

    How do I even go about this? Please help guide me.

    Thank you

  • #2
    Re: Changing network ip addres - HELP!

    Well the first thing I would do is decide what subnet you are changing too. Make sure the subnet has enough ip's for your hosts as well as your network equipment. I did this about 4 months ago. Its going to take some time depending how big of a network you have. Its definately going to have to be done afterhours/downtime.

    Once you figure what subnet your going to use. Then you can setup a dhcp scope on your dhcp server for the clients and put that in place. Then you have to go in and change the ip's on your network equipment (switches/routers/firewalls) Remember to change ip's on vlan interfaces, lan interfaces etc. Also you probably have to change ip's on your servers as well.
    Also if you are hosting any sites accessible to the internet you would need to change your static NATS to point to the new internal addressing scheme. You will also have to change any nat pools and the associated acls so your hosts can get internet access. Also you may have to inform remote sites of the changes as well so they can update their infrastruture so their clients will be able to access resources on your network. If your running any dynamic routing protocols those will also have to alterted to reflect the new networks.

    Take it in steps. Have a good plan in place and its really not that bad.
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)

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    • #3
      Re: Changing network ip addres - HELP!

      thanks auglan,

      I have setup the scope in my DHCP server, also setup all the reservations. Changing the IP manually on all devices shouldn't be too bad.

      My only concern is the ASA and updating all the acls, nta routes and so on. I have never played with asa so i am a bit nervous.

      Are there good tutorials out there that can help me? I have connected to our asa and and now its gui based ASDM. Tutorials based preferably on ASDM.

      thanks,

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      • #4
        Re: Changing network ip addres - HELP!

        Note: why not 192? Personally I'd go with 10.* internally.
        ** Remember to give credit where credit is due and leave reputation points where appropriate **

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        • #5
          Re: Changing network ip addres - HELP!

          There is some good documentation on cisco's site regarding the ASA. I dont use the ASDM that much, usually use the command line. What you can do is just look at the existing nat and acls and adjust them accordingly. I think the ASDM is more cumbersome to play with. The command line is easier to work with in my opinion. Can you get access to the command line via ssh? I think it will look alot clearer looking at the running config then trying to sort it out via the gui.
          CCNA, CCNA-Security, CCNP
          CCIE Security (In Progress)

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          • #6
            Re: Changing network ip addres - HELP!

            @ Wired

            We are going to 10.* internally. The reason we are switching from 192 is because the company is fast expanding and a lot of remote users when vpn(ing) into our system are experiencing wiered issues and i think it is because of these 192 ips. In any case they will be 10.* soon.

            @ auglan

            Yes, i can get into ASA via ssh. I have bought some books. I did print out the running config and am going over it to see where all the internal IP's are being used and with what.

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            • #7
              Re: Changing network ip addres - HELP!

              Originally posted by howithink View Post
              @ Wired

              We are going to 10.* internally. The reason we are switching from 192 is because the company is fast expanding and a lot of remote users when vpn(ing) into our system are experiencing wiered issues and i think it is because of these 192 ips. In any case they will be 10.* soon.
              If your VPN users use the same subnet at home as you do at the office, then yes it is possible that issues could arise. Just be sure to thoroughly test after the switch to make sure you've fixed the problem
              Gareth Howells

              BSc (Hons), MBCS, MCP, MCDST, ICCE

              Any advice is given in good faith and without warranty.

              Please give reputation points if somebody has helped you.

              "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

              "Everything that lives and moves will be food for you." (Genesis 9:3) - For every animal you don't eat, I'm going to eat three.

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              • #8
                Re: Changing network ip addres - HELP!

                Not sure if you have this already covered, but when you do the switchover make sure to shorten the existing DHCP lease time (to a few hours maybe) a couple of days in advance.
                Sure you might have a few clients that might be switched off so a little bit of "floor walking" might be required. You'll have a more than usual congested network but it'll save a lot of hasle depending on how many clients you have.
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