From b6797bbc945f3b5000f3a7d042791bae06f6036a Mon Sep 17 00:00:00 2001 From: Thomas Waldmann Date: Fri, 26 Sep 2014 01:15:24 +0200 Subject: [PATCH] update docs about related hosts feature --- docs/user.rst | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/docs/user.rst b/docs/user.rst index 12c7c27..719d63e 100644 --- a/docs/user.rst +++ b/docs/user.rst @@ -142,6 +142,74 @@ If your DNS hoster does not support dynamic updates, there is some trick how you At the nsupdate.info site, add a host "updatedhost.nsupdate.info" and keep it updated using an update client. +Related Hosts +------------- + +In short: update a whole bunch of DNS records for other hosts on same LAN. + +This is a feature most interesting for IPv6 users, but the same mechanism also +works for IPv4 (it is just rather rare that you get a IPv4 network and you need +dynamic DNS). So, let's assume IPv6 from now on. + +On your main host entry you can configure the IPv6 prefix length (think of netmask). +Usually you'll get a /64 network from your ISP, so keep the default of "64" there +and only change it if you know better. + +The specific prefix you get from your ISP might be static or may change now and +then (for better privacy or other reasons - and in that case, you really need +the related hosts feature). + +You need to configure a dyndns2 compatible updater on some device on your LAN +and the updater needs to send this device's global IPv6 address to the service. + +So far, nothing special, upon receiving an update the service will then update +DNS like this: + +:: + + mainhost.nsupdate.info -> pppp:pppp:pppp:pppp:iiii:iiii:iiii:iiii + +p are prefix parts, i are host/interface parts of the address. + +Additionally, the service will go over all related hosts entries for mainhost +and does more DNS updates based on this computation: + +:: + + relatedhost.mainhost.nsupdate.info -> pppp:pppp:pppp:pppp:rrrr:rrrr:rrrr:rrrr + +You also see it prepends the related host's name to your mainhost's FQDN. + +For the related hosts's address, p is same prefix as above (the host is on same +network), but r comes from what you entered as interface ID into the related +host record. + +In other words: + +:: + + related_fqdn = relatedhost_name.mainhost_fqdn + related_address = mainhost_address_prefix + interface_id + + +Note: + +* enter the static interface ID (usually you can get it from the rear 4 words + of the address that looks like FE80::rrrr:rrrr:rrrr:rrrr). The r part is + usually derived from your hardware MAC address and does not change. +* make sure your device has a IPv6 address with global scope, some prefix that + starts with a "2" and precisely that rrrr:rrrr:rrrr:rrrr value +* you only need a dyndns2 updater on one device (called mainhost in this + example), but the updater needs to find out an address with the same prefix + as seen on your LAN (should be easy if the updater runs on a LAN device, but + might be difficult if it runs on the router and the router has a different + external prefix) +* if you want your mainhost to resolve correctly to some specific device, + make sure you send this device's IPv6 address with the update (myip=...) or + run the updater on that device and make sure the request originates from + the IPv6 address you want in DNS. + + Other Services Updaters -----------------------