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Internet Related/Filtering/Firewall Thread, Broadband install: need to change IP ranges in Technical; Okay guys, newbie question for the geniuses: Situation: New broadband installation is imminent, only I have been told that because ...
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    Question Broadband install: need to change IP ranges

    Okay guys, newbie question for the geniuses:

    Situation:
    New broadband installation is imminent, only I have been told that because our new firewall & filtering is hosted externally (by new ISP) I am going to have change our entire network address range so that it doesn't conflict with another schools network.
    (Never thought this would be a problem being a private range, how wrong I was...)

    Question:
    For someone who's never done anything like this before, what's the best way of going about making all of these changes?
    Are there any things I need to really watch out for?

    Any advice anyone could give would be much appreciated!

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    Michael's Avatar
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    The biggest headache will be to do it in the correct order, but realistically out of hours is best.

    Change your server static IP configuration first, then DHCP, and then printers and any admin workstations with a static configuration.

  3. Thanks to Michael from:

    Asreal (10th March 2014)

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    I would install a NAT box and use your own private IP range for your LAN this will only be a little bit more work and you will never have this issue again if your ISP changes the IP range/

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    I did this not that long ago for one of my schools (went from a /24 to a /22) and it wasnt that bad.

    My process was:

    1. Statically set a laptop my current range and run Angry IP Scanner on the current range (just to get everything)
    2. Change the servers IPs to the new range
    3. Change the DHCP scope to the new range
    4. Change any reservations
    5. Turn the switches off/on again (This causes a re-lease on every device)
    6. Re Run the IP Scan
    7. Change the important devices in the left overs list first
    8. Change the IP Printer ports on the print server
    9. Re Run the IP Scan
    10. Plod through the remaining devices and change them
    11. Repeat Steps 9 & 10 until the IP Scan returns only the laptop you set statically



    In all it took me not much more than on hour to do, most things had a reservation so it was nice and easy.
    Last edited by Arcath; 10th March 2014 at 02:07 PM. Reason: List syntax was wrong

  6. 2 Thanks to Arcath:

    Asreal (10th March 2014), JPShields (17th March 2014)

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    Ensure any IP-based ACLs are updated before swapping the ranges.

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    fairm010's Avatar
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    Quote Originally Posted by Arcath View Post
    I did this not that long ago for one of my schools (went from a /24 to a /22) and it wasnt that bad.

    My process was:

    1. Statically set a laptop my current range and run Angry IP Scanner on the current range (just to get everything)
    2. Change the servers IPs to the new range
    3. Change the DHCP scope to the new range
    4. Change any reservations
    5. Turn the switches off/on again (This causes a re-lease on every device)
    6. Re Run the IP Scan
    7. Change the important devices in the left overs list first
    8. Change the IP Printer ports on the print server
    9. Re Run the IP Scan
    10. Plod through the remaining devices and change them
    11. Repeat Steps 9 & 10 until the IP Scan returns only the laptop you set statically



    In all it took me not much more than on hour to do, most things had a reservation so it was nice and easy.
    I'll be doing this soon, cheers for the list. Does this have any adverse effect on DNS?

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    Michael's Avatar
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    Quote Originally Posted by fairm010 View Post
    I'll be doing this soon, cheers for the list. Does this have any adverse effect on DNS?
    Yes - that's why it's crucial to switch all servers first. Everything in your network relies on DNS. If it fails or it's not working, you will notice problems.

    When changing the IP config, it's important to re-register with DNS manually to speed up the process (via the command prompt). This will then replicate through to other DNS servers on your network.

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    So any clients picking up an IP on the new range will register in DNS ok, providing the servers are all ok first? Also will I have to change my subnet mask?

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    Quote Originally Posted by fairm010 View Post
    So any clients picking up an IP on the new range will register in DNS ok, providing the servers are all ok first? Also will I have to change my subnet mask?
    Correct and possibly. When you're given a new range to play with, all details will be provided. Of course the other crucial part of DNS is your Forwarders. Most LAs setup their own, however you have a choice between the new nameservers at your ISP, or alternatively Google DNS or Open DNS which are generally pretty reliable.

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    Yeah my issues in the week or so afterwards where all down to devices using ip addresses in paths etc... but it didn't cause any major disruption.

    I actually ended doing it twice at one site in less than a month. Our LEA didn't record that we had been given a new range and gave it to someone else, then when we did swap to it (after sitting on the job for 6 months) we had a painful connection with things just not working. I was no impressed when the LEA said I had to change it all again.

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    We've just had our lovely new boradband installed but i've noticed recently we are low on IP's and ideally I want to separate out server and printer ranges. We are currently running on the old LA provided range (255.255.255.0) but can move onto a new one now.

    Just realised I've hijacked the thread, perhaps I should go start my own! Apologies OP :P

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    NP! You're asking thing's I've missed
    (Plus, I'm glad it's not just me!)

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    Quote Originally Posted by Arcath View Post
    Yeah my issues in the week or so afterwards where all down to devices using ip addresses in paths etc... but it didn't cause any major disruption.

    I actually ended doing it twice at one site in less than a month. Our LEA didn't record that we had been given a new range and gave it to someone else, then when we did swap to it (after sitting on the job for 6 months) we had a painful connection with things just not working. I was no impressed when the LEA said I had to change it all again.
    Sounds as though it was a bit poorly managed and I agree - not good changing twice in a short period! Again the slowness can be caused by DNS. If we didn't have DNS we'd have to remember incredibly long strings of numbers!

    I've said to a lot of teachers - Can you remember all the names in your class? 'Yes' - Can you remember all their phone numbers? 'No' - that's what DNS is for

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    Thanks btw folks; has been a great help!

    Rumour has it that some of our extreme switches have had their IPs configured manually - anyone had to do this very much?

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    Quote Originally Posted by fairm010 View Post
    We've just had our lovely new boradband installed but i've noticed recently we are low on IP's and ideally I want to separate out server and printer ranges. We are currently running on the old LA provided range (255.255.255.0) but can move onto a new one now.

    Just realised I've hijacked the thread, perhaps I should go start my own! Apologies OP :P
    A subnet of 255.255.255.0 will be a Class C network, giving you 254 IPs. Depending on the size of your school, it most likely isn't enough. You have to take into account many users connect their Smartphones to the WiFi too and it soon adds up!

    Try reducing the lease time down to 3 days in DHCP Server, so it frees up more IPs in a shorter period of time.

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