New Raspberry Pi 4B user - IP address allocation?

**BigMackCam** · 05-08-2020, 12:48 PM

So... I recently acquired a Raspberry Pi 4B. I've it set up running Raspbian Buster just fine, and connected it to my ADSL router / modem using wifi.

My ADSL router is DHCP enabled to dynamically allocate IP addresses to all of my connected devices. Since I'll need to repeatedly connect to the Pi from other devices (both for SSH and VNC control, and for some forthcoming projects), I want to set a static IP address for it.

Normally, to do this, I would access my router's DHCP config page (gateway address 192.168.1.1), list all of the connected devices and then add a reserved IP address for the relevant device... but I don't see the Pi in the connected list, even though it's definitely connected and accessing the router just fine. Checking the wlan0 IP address for the Pi, I note it as 192.168.1.102, and I can successfully access it from another machine with SSH or VNC Viewer using this address - but I don't see that in my list of connected devices (nor indeed the "raspberrypi" host name)

Now, if I reboot the Pi - and it doesn't matter how many times I do this - it seems to have the same IP address... which is good, in a way, because it seems as if it's already set up for a static address... but I see no such configuration in the dhcpcd.conf config file. I'm confused

Can anyone shed any light on why I'm not seeing a device with the 192.168.1.102 address in my router's DHCP list, and why I repeatedly get the same address for my Pi without any apparent config settings to force this?

If I add the necessary settings to that config file, I can set a different static IP address, so I'll do that anyway...

As you can probably tell from my descriptions above, I'm not experienced in networking. Nor am I especially experienced in Linux at the command line level (though I can work my way around with instructions), and I'm absolutely new to the Pi and Raspbian.

Thanks in advance

Last edited by BigMackCam; 05-08-2020 at 01:38 PM.

bertwert · 05-08-2020, 01:00 PM

Have you tried rebooting the router?

**BigMackCam** · 05-08-2020, 01:08 PM

Originally posted by bertwert

Have you tried rebooting the router?

I haven't, bert, but I can refresh the DHCP config page and see items appear and disappear as I connect and disconnect them from the network...

crazy4oldcars · 05-11-2020, 06:24 AM

DHCP will (tend to) keep IP addresses for devices the same, as long as no new devices are added while one of the existing devices is not present. Then it looks for the lowest unused address. Existing devices get to reuse the same address, unless it has been reassigned.
The trick is to remember what's turned off.....
I messed with setting fixed IP's trying to set time limits on my kids, but that was 10 years ago, so take this with a grain of salt.
I've never messed with anything but windows on a network, so I'm no help on the Pi issues.
A suggestion, though. You be able to look up attached hexadecimal addresses on the router, to see what is connected.
Compare that against your RP to see if there is a match. The equivalent command in windows, at the command prompt, is IPCONFIG /ALL. Without other switches added, it only displays data, and doesn't make any changes.
Good luck!

Kirk B.

05-08-2020, 12:48 PM	#1
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,674	New Raspberry Pi 4B user - IP address allocation? So... I recently acquired a Raspberry Pi 4B. I've it set up running Raspbian Buster just fine, and connected it to my ADSL router / modem using wifi. My ADSL router is DHCP enabled to dynamically allocate IP addresses to all of my connected devices. Since I'll need to repeatedly connect to the Pi from other devices (both for SSH and VNC control, and for some forthcoming projects), I want to set a static IP address for it. Normally, to do this, I would access my router's DHCP config page (gateway address 192.168.1.1), list all of the connected devices and then add a reserved IP address for the relevant device... but I don't see the Pi in the connected list, even though it's definitely connected and accessing the router just fine. Checking the wlan0 IP address for the Pi, I note it as 192.168.1.102, and I can successfully access it from another machine with SSH or VNC Viewer using this address - but I don't see that in my list of connected devices (nor indeed the "raspberrypi" host name) Now, if I reboot the Pi - and it doesn't matter how many times I do this - it seems to have the same IP address... which is good, in a way, because it seems as if it's already set up for a static address... but I see no such configuration in the dhcpcd.conf config file. I'm confused Can anyone shed any light on why I'm not seeing a device with the 192.168.1.102 address in my router's DHCP list, and why I repeatedly get the same address for my Pi without any apparent config settings to force this? If I add the necessary settings to that config file, I can set a different static IP address, so I'll do that anyway... As you can probably tell from my descriptions above, I'm not experienced in networking. Nor am I especially experienced in Linux at the command line level (though I can work my way around with instructions), and I'm absolutely new to the Pi and Raspbian. Thanks in advance Last edited by BigMackCam; 05-08-2020 at 01:38 PM.

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05-08-2020, 01:00 PM	#2
bertwert Veteran Member Join Date: Jun 2015 Location: Golden, BC Posts: 15,173	Have you tried rebooting the router?

05-08-2020, 01:08 PM	#3
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,674 Original Poster	Originally posted by bertwert Have you tried rebooting the router? I haven't, bert, but I can refresh the DHCP config page and see items appear and disappear as I connect and disconnect them from the network...

05-11-2020, 06:24 AM	#4
crazy4oldcars Senior Member Join Date: Jan 2017 Location: Beaumont, Texas Posts: 218	DHCP will (tend to) keep IP addresses for devices the same, as long as no new devices are added while one of the existing devices is not present. Then it looks for the lowest unused address. Existing devices get to reuse the same address, unless it has been reassigned. The trick is to remember what's turned off..... I messed with setting fixed IP's trying to set time limits on my kids, but that was 10 years ago, so take this with a grain of salt. I've never messed with anything but windows on a network, so I'm no help on the Pi issues. A suggestion, though. You be able to look up attached hexadecimal addresses on the router, to see what is connected. Compare that against your RP to see if there is a match. The equivalent command in windows, at the command prompt, is IPCONFIG /ALL. Without other switches added, it only displays data, and doesn't make any changes. Good luck! Kirk B.