The V-series-IP panels use a Clear-Com proprietary protocol for local LAN discovery.
Helixnetand LQ are using mDNS to propagate hostnames. But you can always link/pairwithout entering hostnames but IP addresses instead.

IP Panel discovery
CPU card broadcasts aproprietary discover message when requested by EHX.In this message is the IPaddress of the 1^st configured IVC32 card.Any panels that received thediscover message login to the IVC32 card with the specified IP address.The CPU card caches a list ofall panels that have logged into it and sends this list up to EHX for displayin the IP devices screen. Remote (i.e. not on the localLAN) panels will not receive the broadcast message and therefore will not tryto re-login. Note – If a panel is alreadyconfigured up to login to an IVC32 card it will be added to this CPU card listwhenever it logs in. This is why remote panels sometimes appear in the EHX IPdevices screen.    EHX Matrix Discovery The CPU card sends out an statusmessage every second. If EHX receives this it will include the frame in itslist of discovered frames. This is again a proprietary protocol. One interesting note here isthat when multiple frames are in a linked set that traverses multiple networksand EHX on any of the networks will discover all the frames in the linked set asthe frames relay each other’s frame status message to their LAN segment ifrequested i.e. the broadcast proxy functionality added in HX 7.1
*mDNS - adds multicast DNS service discovery, also known as zeroconf or bonjour to Node.js. It provides an object based interface to announce and browse services on the local network.