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  NETng IP Migration, 2nd Step
Annoucements Posted by Axel Beckert on Tuesday October 16, @05:38PM
from the shiny new ip addresses dept.

During the next weeks, we will be switching over step by step the computers in our network to the final IP range intended for the Physics Department as part of the NETng migration. All hosts in the IP range (other ranges are not affected) will move into the range which means that the first three bytes of the IP address will change.

Every computer not having a static IP address (i.e. nearly all notebooks) will get its address in the new IP range during the night from next Monday to next Tuesday (22./23. Oct. 2007).

Update Monday, 22. Oct. 2007, 21:21: The switch of the dynamic addresses to the new IP range has been made and seems to work generally. Some of the popular Allied Teleysn AT-AR220 NAT routers seem to not accept new IP addresses during usage, but switching them off and on again should help.

All of our managed workstations (Linux, Windows, Macs) will be rebooted during the next weeks for the change, too.

Please read the whole article for details and implications.


  • Connections over the network which are open at the moment the IP changes will be disconnected.
  • If you connect to a machine with one of the new IP addresses, your application (i.e. SSH) may warn you about the changed IP address.
  • If you have any of the bare IP addresses configured (e.g. in your firewall at home), you must change them there, too. (Hostnames don't change and all DNS based configurations should work, but may need a restart.)
  • Outside ETH, it may take up to one day until the address changes have been propagated through DNS, so you may need to calculate the new IP addresses manually. See below.

Static IP addresses

Anyone who has an active machine with static IP address registered as administrator will be contacted by us for migration.

Things you may need to do if you are the administrator of a machine with a static IP address in the ranges 195.176.48.*, 195.176.49.*, 195.176.50.* or 195.176.51.*:

  • Change the network configuration if the machine doesn't use DHCP to set it's static IP address
  • Reboot the machine after the IP change has been done
  • Change firewall rules on the machine itself or other machines depending on that machine.
  • Reconnecting or rebooting clients of that machine

Calculating the new IP addresses manually

The IP range will change from to So the first two bytes of the IP address will change from 195.176 to 192.33 for all hosts. The last byte will stay the same for all hosts. And the third byte will have the same offset to the third byte network's base address. So if the third byte of the old IP address is 49 (difference to base address 48 is 1), the third byte of the new IP address will be 97 (difference to base address 96 is 1).

A small table should help to calculate new IP addresses easier:

Old addressNew address

The new dynamic IP address range will be to with a few gaps.

Student and Seminar Workstations

  • Student Workstations are running on the new IP addresses since Friday evening.
  • Seminar Workstations are running on the new IP addresses since Sunday.

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