APC PDU configuration trick

I was trying to configure an APC7811 PDU, which has a network port for remote access. It’s a metered PDU so you can log in remotely and look at power consumption.

I’d never had to configure one before so I just popped in the CD that came with it and tried to configure an IP address by using the discovery tool. Regardless of which IP address I tried, I kept getting “The IP is already in use on the network.”

This configuration method is in the documentation, but it’s buried at the end… I think I’ll use this every time now as it’s fast and doesn’t require the vendor’s CD.

The MAC address is on the back of the PDU and on the Quality Assurance slip included in the package.

  1. Use ARP to define an IP address for the PDU,
    and use the PDU’s MAC address in the ARP
    command. For example, to define an IP
    address of for the PDU that has
    a MAC address of 00 c0 b7 63 9f 67, use one
    of the following commands:

    Windows command format:
    arp -s 00-c0-b7-63-9f-67

    LINUX command format:
    arp -s 00:c0:b7:63:9f:67

  2. Use Ping with a size of 113 bytes to assign the
    IP address defined by the ARP command. For

    Windows command format:
    ping -l 113

    LINUX command format:
    ping -s 113

  3. Use Telnet to access the PDU at its newly
    assigned IP address. For example:


  4. Use apc for both user name and password.

At this point the IP address is configured for the interface, you can browse to the IP via HTTP. Don’t forget to delete your static ARP entry.


  1. L

    I had a ‘cool’ moment when it worked for me like this :-

    – the APC PDU was a decommisioned-repurposed one – it had a static IP configured, so it wasn’t even sending a DHCP request
    – but i had a Mikrotik router about – i connected (probably, it should be to an interface with an IPv4 address and subnet attached) the PDU to it
    – then I used the Tool -> IP Scan feature, on the interface, WITHOUT entering the destination network to scan, JUST the interface
    – this MIGHT take a while – but it eventually had detected THE static IP with matching MAC address
    – I configured a /24 subnet, such that it would contain THE static IP of the PDU and attached it to the same interface as secondary IP address
    – and used ssh (telnet was disabled) to log in to the PDU, from the Mikrotik (Tools -> Telnet, choose SSH and enter the apparently not-changed-by-previous-user username ‘apc’, and it logged in)
    – using the ssh from Mikrotik i have been able to change settings of the PDU (but trying to use e.g. PuTTY, it wasn’t happy to work with, could be possible maybe to use PuTTY but this was likely due to the PDU ssh implementation being old)
    – the PDU is now working for me as I inteded 🙂

  2. Mutlu Basdas

    wow commenting to this post on 2021!! :))

    I have purchased an used APC AP8941 and can not figure out how to set an IP. Do I need to be connected with the serial cable? I tried with only ethernet cable both connected to the same router, laptop also hardwired obviously. I’m not really an IT person so I don’t think I really know what I’m doing to begin with.
    But I tried the arp command and it didn’t work. Also the PDU is showing a IPv4 address already when I scroll through PDUs menu.

    How can I connect to the PDU, let me know please.


    1. pkremer

      I think this post was the last time I touched one of these units. As far as I remember the ARP command only works for an unconfigured unit. If the unit is already configured, I think you’re going to have to go the serial cable route. Alternatively you could change your laptop to the same subnet that the existing IP is on and then use telnet or SSH to remotely access the command line interface, and change the IP that way.

      I found this document that should be the right user manual for the unit you specified: https://download.schneider-electric.com/files?p_Doc_Ref=SPD_JSAI-7WFQKR_EN

    1. pkremer

      Theoretically if you plug the PDU into a managed switch, you should see the mac address in the switch’s address table (.ie. show mac address-table on a Cisco switch). If the PDU has a static IP on it and for some reason isn’t generating any traffic, you might have to do a hard reset. Then when you plug it in the PDU should issue a DHCP request and then you’ll see the MAC.

  3. Tom

    I was very fortunate that I did a little Google search and found this. It took all of 10 minutes from the time I read this note to getting the PDU set up. I was also lucky that it still had the default user name and password which made it easy. Thank You very much. Tom

  4. Spencer C

    I just ran across this issue and used the netsh neighbors command. Below is the example of what I did to achieve the same results. My network interface was my wifi adapter, your’s might be Local Area Network, etc. The MAC is x’ed out. I was then able to access the Metered PDU via http. The model I did this against was apc pdu 885-1736.

    C:\WINDOWS\system32>netsh interface ipv4 add neighbors “Wi-Fi” XX-XX-XX-XX-XX-XX

    C:\WINDOWS\system32>ping -l 113

    Pinging with 113 bytes of data:
    Reply from bytes=113 time=102ms TTL=255
    Reply from bytes=113 time=4ms TTL=255
    Reply from bytes=113 time=3ms TTL=255
    Reply from bytes=113 time=5ms TTL=255

    Ping statistics for
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
    Approximate round trip times in milli-seconds:
    Minimum = 3ms, Maximum = 102ms, Average = 28ms

  5. Luca

    I have a apc ap7920 that used in webfarm, now I want to set it up again, but I can not connecting to the router to assign an ip … how can I do?
    thank you

  6. hirni

    Interesting entry point.
    OTOH – I went down a different path, as I got a PDU, which was already configured:

    a.) find out it’s MAC address.
    either printed on the pdu, or via some ‘other’ means – like the MAC-table of your (managed) switch.

    so let’s assume I have: 00:c0:b7:31:91:8d

    b.) then – on a linux-client ‘snoop’ for this address:

    tcpdump -i eth0 ether host 00:c0:b7:31:91:8d

    …normally – if you reboot/reset/restart/power-cycle the pdu – it should spit out some ARP requests for ‘some’ configured IPs (like log-server, time-server)
    …and voila – you have the IP-address.

    c.) again assuming you’re on a different network:
    Let’s say your ‘normal’ eth0-net is
    And let’s assume the PDU ‘said’:

    ifconfig eth0:1 netmask 0xffffff00

    d.) ping – if it answers – OK, if no answer:
    likely your netmask isn’t correct, and you need to try some other netmasks (but typically it’s ok with /24)

    e.) telnet / http / ssh test-access the pdu.

    I got lucky – the username/pass was still ‘apc/apc’ – so I could configure it – for my network (DHCP) 🙂

  7. matt

    Great post! I’ve been fighting with this thing and it’s still not working. I have it on my home network using a regular cat 5 Ethernet cable. Do you need to use a crossover cable and directly connect it to your pc? For as much as these devices cost I can’t believe how old school this config is! Thanks a TON!

    1. pkremer

      As long as you’re on the same broadcast domain, the trick should work. When I wrote the post, the PDU and my laptop were connected to a Cisco 3750 switch and on ports in the same VLAN. If you’ve got a simple home switch like a Linksys or whatever, you should just be able to plug both into your switch. But it wouldn’t hurt to plug directly in via crossover cable, I’d expect that to work as well.

  8. Val Langmuir

    I spent I think 2 hours trying the APC config wizard and it kept failing with stupid errors. When I tried the manual command, it sensibly told me I needed to run as administrator. In all fairness the app would have probably worked fine if I had thought to “run as admin”. But your trick is way smoother and worked perfectly! Thanks!!

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