How to enable Dynamic Join/leave

WHAT TO EXPECT
In this article, users will learn how to enable and disable dynamic join/leave for groundSwXtches and how to set allow/block rules for multicast joins and leaves.

This page is organized into the following functions:

For information on static vs. dynamic, refer to Using groundSwXtch User Interface - What is Static vs Dynamic?. Dynamic is off by default on every node. The allow/block rules only govern automatic joins, not routes you add manually with Add Source or Add Destination.

Enable Dynamic Join/leave

To enable Dynamic join/leave:

Select the ⇄ Dynamic join/leave button.
The side panel opens to enable Dynamic Multicast IGMP joins and leaves.
Select one or more groundSwXtches. Use Select visible to pick all groundSwXtches. To clear the selection, select Clear visible.
Select Enable all selected to enable all the selected groundSwXtches.
1. Set allow/block rules. Rules are checked top to bottom and the first match wins. The last rule is a required catch-all that covers everything else.
Select Apply. The map shows that Dynamic is enabled under each groundSwXtch.

Confirmation prompts you may see:

The first time you turn it on for a node, you choose the default for streams no rule covers: Allow all or Block all. You're also offered blocks for UPnP/SSDP, mDNS and LLMNR, which are local-network device-discovery traffic. Those are pre-checked and recommended.
If another querier is already on the local network, you're warned that turning Dynamic on will compete with or take over from it. A querier is the device that asks local devices which streams they want.
If a new block rule would stop streams that are flowing now, it lists them before cutting them off.

Disable Dynamic Join/leave

To disable Dynamic join/leave:

Select the ⇄ Dynamic join/leave button. The side panel opens to disable Dynamic Multicast IGMP joins and leaves.
Select one or more groundSwXtches. Use Select visible to pick all groundSwXtches. To clear the selection, select Clear visible.
Select Disable all selected.
Select Apply.

Participate in Dynamic Multicast

This section only applies when a single groundSwXtch is selected.

Select or deselect groundSwXtches until only one is selected, as shown below:
Turn on the Participate in Dynamic multicast switch (or turn it off to disable).
Select Apply.

Add Allow/Block Rules

Individual groundSwXtches can have more rules to allow or block multicast traffic. Some rules are set automatically, as shown below.

To add more allow/block rules:

Select the Add Rule icon. The side panel expands to enter the rule.
Select the Known Use drop-down to pick the type. Choosing one of the common discovery protocols (UPnP/SSDP, mDNS or LLMNR) fills in its address for you. Custom IP / CIDR / range lets you enter your own. The remaining steps are for Custom IP / CIDR / range.
Select the action: Allow or Block. Allow lets this node join matching streams when devices ask for them. Block stops it.
Select the Match Form: Single IP for one group, CIDR for a block of groups (e.g. 239.1.1.0/24), or IP range for a start and end address.
Enter the Address/Range in the format of the selected Match Form (Single IP, CIDR, IP range). The formats are below:

A range has to be written with a hyphen between two full addresses, for example 239.0.0.1-239.0.0.99. A slash is only for CIDR notation.

Accepted formats:

Match form	Format	Example
Single IP	one address	`239.0.0.1`
IP range	full start address, hyphen, full end address	`239.0.0.1-239.0.0.99`
CIDR	address, slash, number from 0 to 32	`239.0.0.0/24` (covers 239.0.0.0–239.0.0.255)

Every address must be a multicast address (224.x.x.x to 239.x.x.x), and the start of a range can't be higher than the end. Spaces around the hyphen are fine.

Enter a label. The label is a display name that fills itself in (for example, "allow · 239.0.0.1") until you type your own; it doesn't affect which streams match.
Select Add rule.
Select Apply. The rule is not added until you select Apply at the bottom of the form.

Edit an Allow/Block Rule

A rule can be edited after it is added.

To edit an allow/block rule:

Select the Edit Rule icon.
Change what is needed.
Select Save changes.

Allow/Block Rule Priority

Change the order of the rules to set their priority.

How the arrows behave:

↑ moves a rule one place up, giving it higher priority. It's greyed out on the top rule.
↓ moves a rule one place down. It's greyed out on the last rule above the catch-all, because nothing can go below the catch-all.
The catch-all ("Any multicast group", with the 🔒) has no arrows. It's always last and only handles requests that no other rule matched.
The ⠿ handle on the left does the same thing as the arrows, by dragging.
Apply: a reorder isn't saved until you select Apply.

Order matters when rules overlap. Say you add:

Allow 239.1.1.0/24 (all groups from 239.1.1.0 to 239.1.1.255)
Block 239.1.1.5 (one group inside that range)

With Allow on top, a request for 239.1.1.5 matches the Allow rule first and gets through, so the Block rule never takes effect. Moving the Block rule up above the Allow rule blocks 239.1.1.5 while still allowing the rest of the range.

The rule of thumb is to put specific rules (single addresses and exceptions) above broad ones (CIDR blocks and ranges).

Delete an Allow/Block Rule

A rule can be deleted if it no longer applies.

To delete an allow/block rule:

Select the Delete Rule icon.
Select Apply. The rule isn't deleted until you select Apply at the bottom of the form. If a matching stream is running, a warning is shown; otherwise the rule is deleted without a warning.