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Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

tk3000
Aspirant

RAX40 Router unable to assign a reserved IP to some devices (MACs)

Hello,
My router normally assigned IP dynamically via its dhcp server. But, in order to keep track of my devices more consistently, I decided to assign specific IP addresses to specific devices (MAC addresses). Note that by devices, I mean any node connected to my LAN or WLAN (IoT, printer, computers, stream device, etc). For some devices, whenever I try to assign a specific IP address to a given device on the router's interface/dashboard (Advanced > Setup > LAN Setup), the following error message pops up:

"Edit DHCP reservation failed!
This screen will automatically return to the previous screen in a few seconds..."


I double checked any possibility of IP conflicts, etc. No issue there.

Firmware Version V1.0.4.102_1.0.1


Any insights would be appreciated.
-tk3000

Message 1 of 9

Accepted Solutions
Kitsap
Master

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Salt that sequence away, "once I rebooted the router a second time..." you will use that again in the future.

 

You had me shaking my head when you started off a sentence with "The first hundred devices..."

 

It is a good idea to keep a spreadsheet with your device names, IP addresses, and MAC addresses.

 

Please mark this as resolved so others can benefit from the discussion.

View solution in original post

Message 8 of 9

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Kitsap
Master

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Thoughts to consider:

 

The discussion is about IPv4 addresses, not IPv6.

 

Make sure your new chosen IP address is within the range you established in the LAN setup for your DHCP server.  There is a range start and stop point configured in the router.

 

Different devices behave differently, but usually you cannot change an IP once assigned with the devices powered on and the connection made.  To change that IP address, you would need to power down (pull the power cord) for the device to break the connection.  Then make the changes in your router and power it down (pull the power cord).  You might have to power down and restart your router before you can make the IP address assignment.  When you start them back up, power up and let the router stabilize first before powering up the device.

 

Many devices have multiple MAC addresses.  My smart TV has one for the 2.4 GHz radio, one for the 5 GHz radio, and one for the Ethernet port.

 

Message 2 of 9

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Remember too that there are different ways of assigning IP addresses to devices. You can do it on the router with Address Reservation.

 

On many devices you can set the IP on the device itself. I do that on NAS boxes and printers.

 

Which route you take depends on the device and what you have in mind.

 

Message 3 of 9
tk3000
Aspirant

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Kitsap & michaelkenward:

Yeah, all the nodes are in the same subnet (255.255.255.0 mask for 192.168.1.0). The first hundred devices are supposed to have their IP addresses assigned by the devices themselves (static), including the router itself (192.168.1.1); so these addresses are out of the scope of the dhcp server. 


The dynamically assigned IPs are leased randomly within the remaining pool of IP addresses or the router's dhcp server assign them in a reserved fashion (specific IPs to specific MACs). As of now, I am trying to set up the router so that most IPs will be assigned in a reserved fashion by the dhcp server (specific IP to specific device/MAC). So, there should be no conflict. All in all, there are three block of IP addresses: 1) static block; 2) reserved assigned by dhcp server; 3) randomly assigned by dhcp server.


I tried to to do what you suggested, turn off the power to a device connected to the network and then use its MAC address to reserve a given IP to the device on the routers interface. But whenever I try to check and look up the attached devices in the routers web interface, the device turned off seems to still be there present (I refresh the attached devices table/list to no avail).


Typically, what I do in this type of situation is a ping sweep/scan of the network (I use nmap: "nmap -sn 192.168.1.0/24" or "nmap -sP 192.168.1.0/24"). But to my surprise nmap is only returning /reporting 3 hosts/ips up, and I know that there are at least 11 nodes in my LAN/WLAN; which is really odd.


I did not power down the router though, just rebooted it. I will try to physically power it down in my next attempt.

 

Thanks!

Message 4 of 9
Kitsap
Master

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

At any one time, how many devices do your have connected to or attempting to connect to your RAX40?

 

 

Message 5 of 9
tk3000
Aspirant

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Normally, there are between 10 to 14 devices in my network (LAN and WLAN) at any given time. But most of them are dormant or inactive (like cell phones, tablets, stream device in standby, etc)


In the past (months) whenever I would ping scan my network between 10 to 14 devices would show up (hosts up). For some unknown reason, today when I did a ping sweep/scan of the network only 3 hosts were up (it should be between 10 to 14). Concomitantly, whenever I check on the router web interface for the currently attached devices, it shows about 11 devices -- but in my experience the list of attached devices shown by the router is not always up to date, even if I refresh it every so often. Anyhow, there should not be such a huge discrepancy (3 to 11). Typically there would be no difference or a difference of one or two, for example: 13 nodes listed as attached by the router and 11 nodes listed as up in a ping sweep.

Message 6 of 9
tk3000
Aspirant

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

It seems that the problem with ping sweep/scan was related to some glitch in the router. Once I rebooted it a second time, the problem went away and a ping sweep shows all devices/nodes in the network.


Also, I was able to reserve IP addresses to devices once the devices were off and the router itself was rebooted.

 

Thanks!

Message 7 of 9
Kitsap
Master

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Salt that sequence away, "once I rebooted the router a second time..." you will use that again in the future.

 

You had me shaking my head when you started off a sentence with "The first hundred devices..."

 

It is a good idea to keep a spreadsheet with your device names, IP addresses, and MAC addresses.

 

Please mark this as resolved so others can benefit from the discussion.

Message 8 of 9
tk3000
Aspirant

Re: RAX40 Router unable to assign a reserved IP to some devices (MACs)

Yeah, I should started the sentence with "the pool of the first 100 IP addresses are kept for the static use, and out of the scope of the dhcpd."


Sure enough, I will mark it as resolved.

Message 9 of 9
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