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Strange failure to release manually-assigned IP address. Any ideas why? (AX-92U)

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DrFrankenscript

Occasional Visitor
Hi everyone,

Last Friday evening, I was trying to swap in a new server, directly replacing a previous computer, using the same IP address. Both old and new servers are extremely plain setups with Windows 10 using DHCP for fetching their IPv4 addresses, and only one piece of non-windows software on them.

The old server was assigned IP address x.x.x.23 by using the router's manually assigned IP list on the LAN page(I've got about a dozen manually assigned IPs). This address is important because several clients are configured to point to that address to interact with the server.

The process I used was:

1. At the LAN page, removed the reservation for address 23 from the manual assignment list. Clicked Apply to save the changes. This was actually done a few hours before I continued the process. The old server had no reason to change IPs until I was ready to continue and was still 23 at the time of the swap.
2. After configuring the new server for everything except IP stuff, I shut down the old server, physically removed it from the network. Pulled the data hard drives, swapped them into the new server, and put new server into place. Booted it up, and it came up with address x.x.x.160 as its DHCP-assigned address.
3. Went into the router's manual assignment list, selected the new server by name and MAC address, edited the address I wanted from 160 to 23, clicked the + to add it, then clicked apply. After the list refreshed, it showed properly the new name/MAC of the new server and that it would be assigned address 23.
4. Rebooted new server, expecting it to now come up as address 23.
5. New server still showed 160 as its address, in the router clients list and via ipconfig on the server. Checked the manual assignment list in the router, it still showed that this server should be assigned 23. Double checked, no other device was using 23. Tried ipconfig/release / renew a few times, no help.
6. [note, I went through this exact same above process last August with the prior swap for this server, it worked first try then]
7. I removed the manual assignment from the list, then entered it again. Clicked Apply. Rebooted computer. No difference; server still shows 160. Applied updated firmware available to all MeSH components, rebooted routers and new server, no difference.
8. Now in a bit of a rush, I went into the server's adapter properties and manually set it to 23 with appropriate subnet mask etc. Rebooted. No joy. In fact, now it had no internet access at all. This suggested the Router was refusing to allow it to be 23, suggesting it never really released the address, despite me being able to set a new reservation for it in the list.
9. Set the server back to DHCP. Rebooted. This time it came up as address 157. Sighed: What-Ever!
10. At this point I realized something was screwing me up and I was unlikely to fix it immediately. So I went to plan B:
11. In the manual assignment list on the router, I set up an entry for the new server for address 24. Haven't used that address in recent memory. Applied it, rebooted server, it now comes up as x.x.x.24 So, I wasn't forgetting any steps or anything.
12. Reconfigured various clients to point to 24 instead of 23.

System now working perfectly fine, on address 24, but I remain vexed by why I wasn't able to use the freed-up address. Particularly since I did this dance in August and it worked perfectly, then.


While I no longer need to "fix this" I'm really curious as to why it happened, and how to handle it if I run into this problem again in the future. Thanks!
 
I assume you never rebooted router after these changes.
Arp table issue maybe?
 
Last edited:
Just a thought - how are you rebooting your router, from the GUI or via the switch on the router itself? I'd be tempted to switch everything off for half an hour or so and then switch the router back on and leave it for 10 minutes or so to settle down before switching your server and any other network devices back on. This has always worked for me whenever I've had a similar issue, although my router is the RT-AX88U model.
 
Just a thought - how are you rebooting your router, from the GUI or via the switch on the router itself? I'd be tempted to switch everything off for half an hour or so and then switch the router back on and leave it for 10 minutes or so to settle down before switching your server and any other network devices back on. This has always worked for me whenever I've had a similar issue, although my router is the RT-AX88U model.
Good thought. The reboot was automated by the firmware upgrade, not by pulling the plug. Next time I encounter this, I'll try yanking the plug.
 
One other thing that you might want to consider is removing the Ethernet cable from the server after making the change and rebooting with it disconnected. Then plug it back in and see what address it pulls.

I have had weird NIC issues in the past that this procedure has corrected. I don’t know if the NIC is getting enough power from the Ethernet connection to keep it active during a reboot or not, but it acts as though it does on these types of occasions.

Good luck!
 

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