Netgate SG-1000 microFirewall

Author Topic: Finding static IP addresses of exisiting devices with a new router  (Read 211 times)

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Offline dplunk29

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My primary PFsense router died yesterday, and knowing this day might come I had a backup router waiting in the network rack, flashed with the same config ready to go in case this day ever came. I turned it on and internet was restored in about 5 minutes.  :D

My victory was short lived as while the internet is working. The last backup I had was 6 months ago :( and I had added several new devices with static IP addresses since then. Now those devices are still working and I am able to ping those devices, but they are not showing up under the DHCP leases tab in the Pfsense admin panel.

Currently, the only way I know of to get a new device to show up in the DHCP leases of the Pfsense admin panel is to wipe the static IP of the device, and let it grab a new IP address from the DHCP pool and then assign the static IP address.

My question is there a way for the Pfsense router to detect the current static IP addresses on the network without me having to repeat the above process on every device?

I attached some screenshots for a visual example of what I am talking about. The printer IP is 10.2.111.28 and it responses to a ping test, prints, and I can access the web portal, but it does not show up in the Pfsense DHCP leases.

Offline JKnott

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #1 on: January 25, 2018, 08:57:26 pm »
No, there isn't.  However, why are you going through all that trouble.  Instead of assigning static addresses, why not just map an IP address to a static and leave it like that?  Other than my main desktop computer, I do that for all my other devices.

Offline NogBadTheBad

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #2 on: January 26, 2018, 07:27:00 am »
You could run nmap and do a scan of the subnet, that should give you the mac address to IP address so then you could update your DHCP reservations.

[2.4.2-RELEASE][admin@pfsense]/root: nmap -sP -PR 172.16.2.0/24

Starting Nmap 7.40 ( https://nmap.org ) at 2018-01-26 13:18 GMT
Nmap scan report for timecapsule.xxxxxxxxxx.net (172.16.2.6)
Host is up (0.0015s latency).
MAC Address: 6C:70:9F:D8:3B:4E (Apple)
Nmap scan report for nas.xxxxxxxxxx.net (172.16.2.10)
Host is up (-0.20s latency).
MAC Address: 00:11:32:4C:81:69 (Synology Incorporated)
Nmap scan report for pi-2.xxxxxxxxxx.net (172.16.2.11)
Host is up (-0.20s latency).
MAC Address: B8:27:EB:EE:7F:AA (Raspberry Pi Foundation)
Nmap scan report for mac-pro.xxxxxxxxxx.net (172.16.2.20)
Host is up (0.0034s latency).
MAC Address: 00:3E:E1:C1:AF:07 (Apple)
Nmap scan report for w7-vm.xxxxxxxxxx.net (172.16.2.30)
Host is up (0.0061s latency).
MAC Address: 00:50:56:29:C2:92 (VMware)
Nmap scan report for iphone.xxxxxxxxxx.net (172.16.2.40)
Host is up (0.00090s latency).
MAC Address: 40:9C:28:A2:E0:7E (Unknown)
Nmap scan report for mu-so.xxxxxxxxxx.net (172.16.2.55)
Host is up (-0.085s latency).
MAC Address: 30:10:B3:F4:3F:90 (Liteon Technology)
Nmap scan report for 172.16.2.101
Host is up (0.098s latency).
MAC Address: 54:E4:3A:F1:76:A1 (Apple)
Nmap scan report for pfsense-user.xxxxxxxxxx.net (172.16.2.1)
Host is up.
Nmap done: 256 IP addresses (9 hosts up) scanned in 4.03 seconds
[2.4.2-RELEASE][admin@pfsense]/root:

I do DHCP reservations to nearly all my devices, its much easier in the long run IMO.

They should also be in the ARP table if you can ping them.

Diagnostics -> ARP Table

Offline JKnott

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #3 on: January 26, 2018, 08:12:48 am »
Quote
You could run nmap and do a scan of the subnet, that should give you the mac address to IP address so then you could update your DHCP reservations.

Nmap has to be installed first.

Offline dplunk29

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #4 on: January 29, 2018, 12:38:16 pm »
Thanks for the responses guys. I haven't used nmap before and provided all sorts of useful information. As to why I was doing that was keeping my DHCP addresses and static addresses separate. It's an old habit. Mapping to IP addresses does make things easier.

Offline KOM

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #5 on: January 29, 2018, 01:40:50 pm »
Diagnostics - ARP Table will give you a list of clients that pfSense has seen lately, and compare that against your dynamic range.

Offline JKnott

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Re: Finding static IP addresses of exisiting devices with a new router
« Reply #6 on: January 29, 2018, 08:59:09 pm »
Diagnostics - ARP Table will give you a list of clients that pfSense has seen lately, and compare that against your dynamic range.

Arp caches delete entries in a fairly short time.  Also, it requires the pfSense computer to actually receive frames from the devices.