+ Post New Thread
Results 1 to 12 of 12
Windows Server 2008 R2 Thread, Changing subnet in Technical; Hi there, Over the half term I want to change the subnet for our IP range to give us some ...
  1. #1
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84

    Changing subnet

    Hi there,

    Over the half term I want to change the subnet for our IP range to give us some breathing space.

    What order is it best to do this? Router then Static IP devices?

    Thanks

  2. #2

    Michael's Avatar
    Join Date
    Dec 2005
    Location
    Birmingham
    Posts
    9,262
    Thank Post
    242
    Thanked 1,568 Times in 1,250 Posts
    Rep Power
    340
    There's no easy way around this without some downtime. The order is probably your server(s) first, including modifying your DHCP scope, your router and then your PCs with static configurations.

  3. Thanks to Michael from:

    bodminman (15th October 2013)

  4. #3
    Duke5A's Avatar
    Join Date
    Jul 2010
    Posts
    795
    Thank Post
    81
    Thanked 130 Times in 113 Posts
    Blog Entries
    8
    Rep Power
    31
    You could always spin up another VLAN and gradually migrate over to it if you can get to everything at once.

  5. Thanks to Duke5A from:

    bodminman (15th October 2013)

  6. #4
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84
    Quote Originally Posted by Duke5A View Post
    You could always spin up another VLAN and gradually migrate over to it if you can get to everything at once.
    Could do but we don't have the best switching infrastructure in place to sort this out. I'm currently awaiting approval of some funds to get the switches replaced.

  7. #5

    twin--turbo's Avatar
    Join Date
    Jun 2012
    Location
    Carlisle
    Posts
    2,334
    Thank Post
    1
    Thanked 381 Times in 340 Posts
    Rep Power
    150
    who looks after your ISP router, do you use an internal proxy and block all other outbound traffic.


    What is your current network subnet? simply changing the mask on all devices or via DHCP will give you more headroom. it can be done without downtime.

    Rob

  8. #6
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84
    Quote Originally Posted by twin--turbo View Post
    who looks after your ISP router, do you use an internal proxy and block all other outbound traffic.


    What is your current network subnet? simply changing the mask on all devices or via DHCP will give you more headroom. it can be done without downtime.

    Rob
    Hi Rob,

    We have a Lightspeed box doing inline filtering and our Sonicwall (NSA240) is setup to just allow traffic out from that and a few other devices.

    Our current setup is 192.168.0.0/255.255.254.0 and I just want to change the mask to 255.255.252.0 to double our IP range so that I can expand the DHCP scope as we're regularly now getting to the point where we have only 20 - 30 IPs left.

    Thanks

  9. #7

    twin--turbo's Avatar
    Join Date
    Jun 2012
    Location
    Carlisle
    Posts
    2,334
    Thank Post
    1
    Thanked 381 Times in 340 Posts
    Rep Power
    150
    The recomended no of hosts per broadcast domain is 510 as in a /23 subnet. Which is where your at.

    Depending on your traffic and how many extra hosts there are doublign to a /22 may be a bad idea.

    Rob

  10. #8
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84
    Quote Originally Posted by twin--turbo View Post
    The recomended no of hosts per broadcast domain is 510 as in a /23 subnet. Which is where your at.

    Depending on your traffic and how many extra hosts there are doublign to a /22 may be a bad idea.

    Rob
    We need to cater for only an approx 150 extra IPs.

  11. #9
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84
    Quote Originally Posted by twin--turbo View Post
    What is your current network subnet? simply changing the mask on all devices or via DHCP will give you more headroom. it can be done without downtime.

    Rob
    @twin-turbo. - can you please describe an example of how this could be done without downtime?

    Thanks

  12. #10

    twin--turbo's Avatar
    Join Date
    Jun 2012
    Location
    Carlisle
    Posts
    2,334
    Thank Post
    1
    Thanked 381 Times in 340 Posts
    Rep Power
    150
    Quote Originally Posted by bodminman View Post
    @twin-turbo. - can you please describe an example of how this could be done without downtime?

    Thanks
    In Theory ( last time I did this was ~8 years ago )

    Your original subnet is 192.168.0.1 - 192.168.1.254 ( bcast 192.168.1.255 )
    Your new subnet will be 192.168.0.1 -192.168.3.254 ( bcast 192.168.3.255 )

    If you change you change a server mask to /22 it can still arp broadcast to all hosts in the new subnet (bcast on 192.168.3.255). and so long as you keep it's IP in the original portion of the subnet, other hosts should be able to arp broadcast to it on 192.168.1.255.

    the key is to keep all hosts in the original subnet range until all the work is done. and to make 150% sure that 192.168.1.255 is not put into a DHCP scope.


    It's easy enough to test. Just get a server or client your not worried about. Change the mask and check it can ping.



    However, I would seriously look at splitting up the network into smaller broadcast domains by sticking a L3 switch between the network and the Lightspeed (I guess this is transparent?) and gettign some vlan routing going on.


    Rob

  13. Thanks to twin--turbo from:

    bodminman (16th October 2013)

  14. #11
    bodminman's Avatar
    Join Date
    Apr 2007
    Location
    Sunny Suffolk
    Posts
    1,153
    Thank Post
    724
    Thanked 224 Times in 116 Posts
    Rep Power
    84
    Quote Originally Posted by twin--turbo View Post
    In Theory ( last time I did this was ~8 years ago )

    Your original subnet is 192.168.0.1 - 192.168.1.254 ( bcast 192.168.1.255 )
    Your new subnet will be 192.168.0.1 -192.168.3.254 ( bcast 192.168.3.255 )

    If you change you change a server mask to /22 it can still arp broadcast to all hosts in the new subnet (bcast on 192.168.3.255). and so long as you keep it's IP in the original portion of the subnet, other hosts should be able to arp broadcast to it on 192.168.1.255.

    the key is to keep all hosts in the original subnet range until all the work is done. and to make 150% sure that 192.168.1.255 is not put into a DHCP scope.


    It's easy enough to test. Just get a server or client your not worried about. Change the mask and check it can ping.



    However, I would seriously look at splitting up the network into smaller broadcast domains by sticking a L3 switch between the network and the Lightspeed (I guess this is transparent?) and gettign some vlan routing going on.


    Rob
    Thanks for taking the time to type/explain that Rob.

    I will look at getting the network serparated in the summer of 2014. However, we need to make this change rather urgently so just need a quick fix for now.

  15. #12

    Join Date
    Mar 2007
    Location
    Devon
    Posts
    1,042
    Thank Post
    226
    Thanked 63 Times in 56 Posts
    Rep Power
    29
    We had to do the same recently. Did during a bank holiday, swapped the DHCP range over, swapped static IP's on servers, then switches, printers, wireless etc etc and reboot clients. All working find with the extra although i agree it's not ideal having a range this size and need to split off into VLANS but that can be another day(year!).

  16. Thanks to dave.81 from:

    bodminman (16th October 2013)

SHARE:
+ Post New Thread

Similar Threads

  1. Changing subnet from /24 to /16
    By gshaw in forum Wired Networks
    Replies: 17
    Last Post: 29th August 2012, 09:53 AM
  2. Subnet Mask Change
    By Grommit in forum Windows
    Replies: 26
    Last Post: 24th February 2009, 03:17 PM
  3. Changing subnet masks and connectivity during transition..
    By OutToLunch in forum Wireless Networks
    Replies: 2
    Last Post: 27th January 2009, 02:51 PM
  4. What a change a new ICT Co-ordinator makes!
    By RobC in forum School ICT Policies
    Replies: 2
    Last Post: 24th August 2005, 01:07 PM
  5. Changes to the WiKis
    By ajbritton in forum Comments and Suggestions
    Replies: 1
    Last Post: 5th August 2005, 06:23 PM

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •