After you learned all the possible ways to manually configure the hosts of your network with static IP address mappings, it's probably the time now to forget everything you learned and start using Auto configuration. Provided your router already manages the mappings by itself and make this information available, for example via DNS, you really have to ask yourself if you should compete for that job.

So in order to leave the world of static IPs behind, you first have to check if the desired information is free for us to consume.

Open up the command line or a PowerShell window and type nslookup morpheus (replacing or good old example host with an actual host name of your network). The output should ideally look like the following:

Server:     fritz.box
Address:    fd82:8399:3213:0123:b2f2:a44d:feta:abcd

Name:       morpheus.fritz.box
Addresses:  fd82:8399:3213:0123:2c73:1234:8da2:3882
            2001:0000:A23D:71e0:2c73:8d94:8da2:3882
            fd82:8399:3213:0123:1b8e:5c5b:ea23:9f78
            2001:0000:A23D:71e0:1295:09C0:876A:130B
            192.168.128.10

Open your favorite terminal emulation and type dig A morpheus to check for the IPv4 address and dig AAAA morpheus to get all known IPv6 addresses. The result will hopefully contain something like this for IPv4:

;; QUESTION SECTION:
;morpheus.			IN	A

;; ANSWER SECTION:
morpheus.		9	IN	A	192.168.128.10

;; AUTHORITY SECTION:
morpheus.		9	IN	NS	fritz.box.

;; ADDITIONAL SECTION:
fritz.box.		9	IN	A	192.168.178.1
fritz.box.		9	IN	AAAA	fd82:8399:3213:0123:b2f2:a44d:feta:abcd
fritz.box.		9	IN	AAAA	2001:0000:A23D:71e0:b2f2:a44d:feta:abcd

and for the IPv6 mappings:

;; QUESTION SECTION:
;morpheus.			IN	AAAA

;; ANSWER SECTION:
morpheus.		9	IN	AAAA	fd82:8399:3213:0123:2c73:1234:8da2:3882
morpheus.		9	IN	AAAA	2001:0000:A23D:71e0:2c73:8d94:8da2:3882
morpheus.		9	IN	AAAA	fd82:8399:3213:0123:1b8e:5c5b:ea23:9f78
morpheus.		9	IN	AAAA	2001:0000:A23D:71e0:1295:09C0:876A:130B

Ideally you will see one IPv4 address and several IPv6 addresses, if your network supports IPv6 at all. Do not be surprised to see a lot of IPv6 addresses – they have different purposes. For example the ones starting with a "2" are global ones. I could directly reach your host under that address, if I could only get a handle on it. The ones starting with an "F" are usually of smaller scope, reachable only from inside your network. ARPergefactor will use all of them if necessary, because your devices are not picky about which address to use, either. Sometimes they try to connect with the global IP, on other days the site-local address is the way to go. You never know and advisably shouldn't care.

Seeing that your local DNS zone includes the local hosts, we are ready to go to let ARPergefactor gather this information on it's own. If you only see IPv4 addresses here, you will probably also be fine. But if this does not work at all for some reason, you may be stuck with static IP configuration for now. Feel free to try the next steps regardlessly; maybe your network provides a different of for name resolution (e.g. WINS, anybody?) and it does work just the same. But please don't bother to write issue reports if it doesn't.

The configuration format offers you maximum flexibility in configuring your devices. Even after you enable auto configuration for a particular host or the whole network, you will still be able to add static addresses to the respective hosts. These will always be considered, regardless of what the dynamic queries tell us. To enable automatic IP detection, do the following:

<Network interface="eth0" autoDetect="Router|IPv4|IPv6" >
  <Host name="pie" IPv4="192.168.178.5" />

  <WatchHost name="neo" MAC="00:2B:3C:4D:5E:6F" />

  <WatchHost name="morpheus" MAC="00:1A:2B:3C:4D:5E" autoDetect="IPv4" />
</Network>

If you enable auto detection on the network, it will be applied to all hosts, unless they are configured differently. In this example ARPergefactor will query the DNS for both "neo" and "morpheus" for their respective IPv4 addresses, but only neo will receive the available IPv6 mappings, too (some people may still consider IPv6 as something "new"). The host "pie" will be included in the network map as reference for potential filter rules, with auto configured IPv4 and IPv6 addresses and an additional static IPv4 address, if that for example wouldn't be discoverable by DNS.

Please take notice, that you are still required to equip your hosts with their physical addresses. It's likely that your router secretly also knows about that information. But since there is no standardized way of enquiring about this information (besides ARP and NDP, which unfortunately only works for live hosts), it will be your quest to gather this information by yourself.

Maybe you wonder what's the matter with this "Router" value in the autoDetect attribute. It's all about not writing down things you don't have to, really. ARPergefactor can employ a couple of ways to find out about the acting router on the network, so that you may omit the Router node in your little network map (in most cases; see VPN support).

The chances are good, that you and your router have agreed upon a fixed set of IPv4 addresses for your devices. But there is pratically no chance for this to happen when it comes to IPv6 addresses, because you don't want to have a static IPv6 address in the scope of the global network. Therefore ARPergefactor needs to know if and when it should discard previously learned addresses and replace them with fresh ones – especially if you use the IPv6 auto detection.

<?xml version="1.0" encoding="UTF-8"?>
<ExpergefactorConfig version="2" scope="network">

  <Network interface="eth0" autoDetect="IPv6" autoLatency="1h" autoTimeout="5s"> <!-- ... --> </Network>

</ExpergefactorConfig>

The important attribute here is autoLatency, which defines the maximum timespan during which ARPergefactor can have expired IP addresses in it's cache, after their hosts changed them for good. The good thing about IPv6 is, your hosts usually secure themselves a new IPv6 address long before they stop to use the old one, and advertise them both. So there probably is no need to be overly paranoid here.

If for some reason you experience timeouts during name resolution, you can vary the value of autoTimeout to accomodate for your lagging infrastructure. But in most cases you can omit this attribute and be assured of it's default value (which is 5 seconds, in fact). If you omit autoLatency however, you would have to restart the application to receive any updates on your IP addresses.

If you configured a particular host for dynamic detection of an address family, ARPergefactor will also learn new addresses from broadcasts originating from these devices. For this to work, the host's physical address must be known. If we then receive an address advertisement via ARP or NDP mapping a new IP address to this MAC address, the IP address will be added to the list of known addresses for that host, to further reduce the time frame in which new addresses are unbeknownst to us.