With Zoom’s Meeting Connector, organizations can deploy on-premise servers within their network, allowing users to host meetings within the network instead of Zoom Cloud. While this can really help with bandwidth network costs for hosting internal meetings, guest participants outside of the network will not be able to connect to those meetings without additional firewall configuration on the participant and organization’s side.

How to allow guest participants outside your network to join on-prem meetings

Each ZC and MMR server IP must be 1:1 NAT translated to a public IP address. These external IP addresses must be added to each of the Meeting Connector ZC and MMRs in their local interface.

Below are the firewall rules/allowed connections that will need to be implemented for the Guest's firewall  as well as the hosting organization's firewall, to ensure that guests can make a connection to an organization's on-premise meetings:

Protocol	Ports	Source	Destination	Purpose
TCP	80, 443	Zoom Clients within guest/external network	*.zoom.us *.zoomonprem.com	Client Login / Meeting Join Process
TCP	443	Zoom Clients within guest/external network	Hosting Meeting Connector (ZC and MMR external IPs/domains or ZC)	Client Signaling with Meeting servers (ZC and MMRs)
UDP	3478, 3479, 8801	Zoom Clients within guest/external network	Hosting Meeting Connector (ZC and MMR external IPs/domains or ZC) *.zoomonprem.com	Client Audio/Video/Content media to/from Meeting servers (ZC and MMRs)