Amplifi HD - IP address confusion


  • Hello - for the longest time I had my primary HD on a fixed IP address from my router (it’s in Bridge mode). Yesterday I noticed that I could not get to the management page and in looking at my router IP allocation table, I noticed that it had a new IP address. I then created another fixed IP allocation for it thinking that my modem somehow lost the configuration.

    Today I upgraded the firmware to 3.4.1 and my whole network became unstable. The primary HD kept dropping the connection to the modem. I checked the modem IP allocation table and realized that the primary HD had 2 IP addresses 😳. I deleted one of the reservations, restarted the primary HD. Now, my modem only shows one IP address (XXX.ZZZ.Y.86) but I cannot reach the AmpliFi admin page using this address. I can, however, get to it using the other IP address (XXX.ZZZ.Y.109), which according to my modem is not used anywhere.

    I’m pretty sure the ATT U-Verse modems reserve addresses by MAC, so I’m not sure WHY there was a new IP address in the first place. And now how do I get my Amplifi and modem back in sync?

    UPDATE: I think I figured it out - I deleted both reservations and the Amplifi HD pulled the XXX.ZZZ.Y.109 from the pool. I then made this the fixed IP allocation and right now, the XXX.ZZZ.Y.86 is no longer in the IP allocation table.

    Still confused by why there would be a new IP address allocated when I actually had a fixed IP for it. I was on 3.3.0 before the update and I'm wondering if the "new" allocation happened when I upgraded from 3.1.2 (or whatever the previous version was)?


  • Still confused by why there would be a new IP address allocated when I actually had a fixed IP for it. I was on 3.3.0 before the update and I'm wondering if the "new" allocation happened when I upgraded from 3.1.2 (or whatever the previous version was)?

    Hi @Rakesh-Gupta - in order for AmpliFi to implement Hardware NAT in DHCP modes with firmware v2.6.0 they used two MAC addresses for the physical WAN Ethernet port - one MAC address on the upstream WAN facing side, and a different MAC address on the LAN side

    If the HD router was placed in Bridge mode, the LAN side MAC address was published upsrteam since no NAT takes place

    Unfortunately, firmware bugs would also cause the MAC address to randomly flip back and forth between the two MAC addresses when in Bridge mode, and this phenomenon lasted for a couple years

    If you ran you router in Bridge mode with a MAC based reserved IP address, it would sometimes get 'lost' because the MAC address would change, but it would only ever alternate between the 2 MAC's

    Some of us ran 2 separate reserved IP's (one for each MAC) and would have to switch port forwarding rules when things like Teleport would stop working

    Starting with AmpliFi HD Firmware v3.3.0 they stopped the practice of using 2 different MAC addresses between DHCP and Bridge mode...
    https://community.amplifi.com/topic/2663/amplifi-hd-firmware-v3-3-0

    • Resolved MAC address issue when switching to Bridge mode

    "Please be aware that AmpliFi devices may have different IP addresses after the update if using Bridge mode."

    So you are likely seeing some after effects of the update from v3.1.2 to v3.3.0


  • @Derek-Saville said in Amplifi HD - IP address confusion:

    So you are likely seeing some after effects of the update from v3.1.2 to v3.3.0

    Thanks @Derek-Saville. Now that you mentioned it, I do remember some comments on MAC switching. Guess it happened then and I never noticed it till yesterday.


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