Assigning IP Addresses APC PDU via ARP

Introduction

If you have ever ended up in the situation in which you have APC PDUs connected to your network which were never assigned management IP addresses then this is a nifty trick you can use to get them up and running.

Solution

The solution is to use a VM which has interfaces directly in the required networks. In my case I had two VLANs where the devices in question were installed but never setup. You will need root access to the VM as you will need to permanently assign ARP entries and then ping a specific size request to assign an IP to the device in question.

Using a vanilla CentOS 7 install with root permissions, use the following method. Note MAC should be in the following format:

00:aa:11:bb:22:cc

Command:

arp -s <IP address> <MAC>
ping <IP address> -s 113

Of course you will need to know MAC in advance which can either be retrieved directly from your switch or from the devices itself. I was searching for the required devices utilising the manufacturer MAC which was in use for working devices. You can use the following website to confirm:

https://macvendors.com/

Once you’re getting ping replies then you’ll need to telnet to the device and logon. Likley the device will have default authentication details if it has never had an IP configured. If not then you’ll need to reset manaully.

telnet <address>

Once you are on the device you will need to set the subnet and gateway to ensure the device is reachable outside of the local network. WARNING, get this right as the device will accept an invalid subnet mask and then become unreachable!

tcpip -g <gateway address> -s <subnet mask>

After assigning the management card will require a reboot.

reboot

Note the reboot does not affect devices plugged into the PDU, it is simply a reboot of the management card. After the reboot you’ll be able to logon to the device via the web GUI.

Viola. You can configure your device as required. Note to self. Make sure PDU devices are taken care of on rack installation!