Multicast Address Management can help you assign NMOS sender addresses from defined pools without reusing a managed combination of address, destination port, and stream leg. Instead of tracking each sender manually, you define pools and the feature records each allocation.
Category-specific pools can also help your network orchestrator identify each stream's media class and reserve the corresponding bandwidth. For example, an address from a range reserved for HD video can trigger the orchestrator's HD video bandwidth policy. Multicast Address Management assigns the address; the network orchestrator applies the bandwidth reservation.
This guide configures one system-wide auto-assignment profile for a non-production HD video sender. The v1.8 web interface exposes system-wide profiles; Registry- and connection-specific profile overrides are not covered.
Tip
Use dedicated ranges when possible so manually assigned addresses do not overlap with managed allocations.
Before you begin#
You need:
- The NMOS feature enabled in Buttons.
- A Pro or Enterprise license.
- System administration access for NMOS settings.
- An adopted NMOS node with a sender whose SDP and source port are available to Buttons.
- A multicast address range and destination port for the sender category.
- When network orchestration uses ranges to classify streams, a corresponding range-to-media-class mapping.
- Access to the NMOS sender and network monitoring needed to confirm the resulting stream.
Enabling auto-assignment updates eligible senders through IS-05 and activates the change immediately. Start with a non-production sender.
Why manage addresses centrally#
A multicast sender needs a destination address and port before receivers can subscribe to its stream. When these values are assigned manually across many senders, two senders can unintentionally receive the same address, port, and primary or secondary leg.
Multicast Address Management provides one allocation record for managed senders:
- Profiles divide address pools by media category.
- Each allocation is recorded before it is applied to the sender.
- The next sender receives the first available address rather than reusing a managed allocation.
- Current allocations shows which sender holds each managed address.
- Stable category ranges let an external network orchestrator map an address to a stream class and apply the bandwidth policy configured for that class.
The allocation record covers addresses managed here, not addresses assigned manually or by another controller. The external orchestrator uses its own range-to-stream-class mapping to apply bandwidth policy.
How address selection works#
The sender is classified from its NMOS flow and source metadata. Available profile categories include specific formats such as Video HD, Video 4K HDR, and Audio Stereo, plus fallback categories such as Any Video, Any Audio, and Any.
When a network orchestrator uses the assigned range to choose a bandwidth policy, align each profile with the orchestrator's stream-class mapping.
For a classified sender, profiles are considered in this order:
- The sender's specific category, such as Video HD.
- The matching media fallback, such as Any Video.
- Any.
The first unallocated address in the matching profile's inclusive range is selected. An address is considered occupied when an existing allocation uses the same primary or secondary leg and destination port.
A secondary range is optional. Add one only for senders with two interface bindings that use SMPTE ST 2022-7 redundancy. Both legs are assigned together; if the required secondary address is unavailable, the sender's previous managed allocations remain instead of applying only the primary leg.
Add a profile for HD video#
In this example, the network orchestrator maps the HD video range to its HD bandwidth policy. Configure that mapping in the orchestrator when your network uses range-based classification.
- Open Settings → Multicast.
- Under Auto-assignment profiles, select Add Profile.
- Set Category to Video HD.
- Enter the inclusive range in Primary Start IP and Primary End IP, such as
239.100.10.100 to 239.100.10.199. - Enter the destination Port. The initial value is
5004. - Select Add Profile.
The new Video HD card shows the primary range and destination port. The form rejects an address outside 224.0.0.0–239.255.255.255, a range whose end precedes its start, an incomplete secondary range, or a port outside 1–65535.
Enable automatic assignment#
The profile defines which addresses are available. The NMOS behavior determines whether they are assigned automatically.
- Open Settings → NMOS.
- Find NMOS Controller Behavior.
- Enable Auto-Assign Multicast Address.
- Select Save.
Eligible senders are reevaluated when the behavior or multicast profile configuration changes and when changed sender SDP is read. An HD sender receives the first free address in the Video HD profile, and the address and destination port are applied through IS-05.
Open the NMOS
Inventory page's
Multicast allocations tab (linked from
Settings → Multicast's own
Current allocations section). The assigned sender appears with its
Source (
Pool for an auto-assigned address, alongside
Manual and
Adopted: see
Override or renew a sender's address),
Category, address, and leg, plus an on-wire check against the sender's own SDP so drift between the recorded allocation and what the device actually announces is visible at a glance. A single-leg sender appears as
Primary. This record keeps the managed address and port from being assigned to another sender on the same leg.
Confirm that the expected non-production stream is active at the listed address and port. When an external orchestrator uses range-based classification, its monitoring should show the HD video bandwidth policy applied to the stream.
Add a fallback profile#
A specific profile is preferred over a fallback. For example, a Video HD sender uses the Video HD profile even when Any Video and Any profiles also exist.
A fallback gives a broader group of senders access to one pool when their metadata does not match a specific category. Choose Any Video, Any Audio, or Any according to the streams the pool should support.
If no profile matches, no new address is assigned. Review the NMOS logs for a missing-rule warning, then add the appropriate profile or correct the sender's NMOS metadata.
Add a secondary ST 2022-7 range#
For a sender with two interface bindings, you can allocate separate primary and secondary addresses:
- Open Settings → Multicast.
- Add a profile for the required category.
- Enter the Primary Start IP, Primary End IP, and Port.
- Select Add secondary range (ST 2022-7).
- Enter the Secondary Start IP and Secondary End IP.
- Select Add Profile.
When both legs are required, Current allocations shows separate Primary and Secondary rows for the sender. Both legs use the same destination port.
Override or renew a sender's address#
The Multicast allocations tab on the NMOS Inventory page lets you step outside the automatic pool assignment for a specific sender when you need to:
- Override an address: select a sender's row, choose Override address for the primary or secondary leg, and enter a specific multicast address and port. A manual override is kept across rule changes and forced re-syncs until you clear it; the device is re-staged immediately. The override is rejected (with the reason shown inline) if the address and port are already named by a static SDP, already carried by another live sender, or already allocated to another sender on that leg.
- Renew an address: select one or more senders and choose Assign new available addresses to release their current allocation (auto-assigned, manual, or adopted) and draw a fresh one from the matching profile.
- Clear an override: returns a manually-overridden sender to normal pool assignment.
Each of these offers an Update receivers with the new SDP option: on, every receiver currently taking that sender is re-staged with the new address once the device's SDP announces it (up to 15 seconds), regardless of the receiver's own reconnect-on-SDP-change behavior; off, receivers pick up the change on their own next SDP read instead.
If you get stuck#
What you see | What to try |
|---|
Multicast is missing from Settings. | Confirm that NMOS is enabled in Settings → Features and that the system has a Pro or Enterprise license. |
No allocation appears after you save. | Confirm that the sender is adopted, exposes a source port and readable SDP, has Auto-Assign Multicast Address enabled through its behavior configuration, and matches a configured category or fallback. Review the NMOS logs for no matching rule, range exhaustion, or IS-05 staging failures. |
A redundant sender receives no new allocation. | Confirm that both the primary and secondary ranges have a free address. A partial new assignment is not kept when a required secondary allocation fails. |
The allocation appears, but the stream is unavailable. | Check the sender's IS-05 state, multicast network, orchestrator bandwidth reservation, and receiver subscription. |
The network reserves the wrong bandwidth class. | Confirm that the sender's NMOS flow metadata selected the intended profile and that the external orchestrator maps the assigned range to the same stream class. |
Release an allocation#
The Multicast allocations tab lets you select one or more rows and choose Release. Releasing removes the managed record and makes the address available for a future allocation. It does not disable the sender or change its transport parameters, so release the record after the sender has stopped using the address.
Warning
Release takes effect immediately, with no confirmation step. Confirm the sender has actually stopped using the address before releasing its record: otherwise a future allocation could reuse the same address while the original sender is still transmitting to it.
Deleting a profile asks first: the confirmation dialog reports how many active address reservations that profile holds and offers Delete and keep reservations (the profile is removed, but its senders' current addresses stay reserved and cannot be reused) or Delete and release reservations (the same immediate-reuse risk as releasing an allocation directly, described above: confirm those senders have actually stopped using their addresses first).
