Which features does a Dante switch need?

With the advent of Dante devices and thus IP technology in everyday audio engineering, the question arises every day as to which switch is suitable for Dante applications. The requirements are initially extremely low, so that nowadays almost every switch is basically suitable for Dante.

Before we take a look at the most common functions that we find in the marketing brochures of various manufacturers, I would like to point out that in addition to the content-related features, there are of course also purely material aspects. The processing quality, the longevity and reliability over many years, but also the manufacturer support and the availability of replacement devices play just as important a role in the professional environment as the features that marketing likes to emphasize.

Unmanaged or managed does not play a role at first, because the most important thing is that the data packets from the Dante sender arrive unchanged and as quickly as possible at the Dante receiver. The question of “features” of a switch relates more to the environment in which it is to be used, i.e. the number of switches, the cable lengths, the desire for redundancy and failure safety.

As a small outlook for the many features and abbreviations that I would like to take up in the course of the article, here is an overview table of a few common switch models, without guarantee:

Manufacturer	Cisco			HP / Aruba				Netgear
Type*	SG-250 CBS-250	SG-350 CBS-350	9200	1820	1930	2530	2930F	M4250
Ports	1 Gbit	1 Gbit	1 Gbit	1 Gbit	1 Gbit	100Mbit / 1Gbit	1 Gbit	1 Gbit / 2.5Gbit
Uplink-Ports	1 Gbit X: 10Gbit	1 Gbit X: 10Gbit	G: 1Gbit X: 10Gbit	1 Gbit	1 Gbit	1 Gbit	1 Gbit / 10Gbit	1 Gbit / 10Gbit
EEE deactivatable	✔	✔	✔	✔	✔	✔	✔	✔
VLAN	✔	✔	✔	✔	✔	✔	✔	✔
QoS	✔	✔	✔	-	✔	✔	✔	✔
SFP-Slots	⃘	✔	✔	⃘	⃘	⃘	✔	⃘
RSTP / MSTP	✔/✔	✔/✔	✔/✔	✔/-	✔/✔	✔/✔	✔/✔	✔/✔
IGMP Snooping	✔	✔	✔	✔	✔	✔	✔	✔
IGMP Querier	✔	✔	✔	-	-	✔	✔	✔
DHCP Server	-	✔	✔	-	-	-	✔	✔
Web-UI / CLI	✔/✔	✔/✔	(✔)/✔	✔/-	✔/-	(✔)/✔	(✔)/✔	✔/✔
SNMP	✔	✔	✔	✔	✔	✔	✔	✔
19" mountable	⃘	✔	✔	⃘	⃘	✔	✔	⃘
PoE	⃘	⃘	⃘	⃘	⃘	⃘	⃘	⃘
Fanless Models	8/8P/10P/ 18/26	10/10P/28	-	8/8P/ 24/48	8/8P/ 24/48	8P/12P	8P/12P	10
Redundant Power Supply	-	-	optional	-	-	-	-	-

✔  supported     (✔) limited range of functions
⃘   some models
- not supported

Unmanaged Dante Switch

Pretty much any current switch is sufficient for home use. There are two criteria to look out for:

Speed: 1Gbit/s

For a few devices or a few Dante channels, ports with 100Mbit/s are sufficient in terms of transmission speed. As soon as you want to connect several switches with each other, you should definitely choose the 1Gbit/s (1 Gbps) variant for the uplink ports. Even if the bandwidth is sufficient for the few channels, the latency increases significantly more when cascading 100Mbit switches per switch than when using 1Gbit connections.

EEE Functions can be deactivated

Sometimes good-sounding and well-intentioned features also have disadvantages. The energy-saving functions (Energy Efficient Ethernet, sometimes also called Green Energy) can lead to problems with the transmission of Dante signals. The switch tries to save power by efficiently packing the data packets, but ultimately it messes up the continuous flow of transmission. It should therefore be possible to deactivate these functions. The problem with unmanaged switches: due to the lack of a web interface, no changes can be made to the switch. In this respect, all unmanaged switches that advertise EEE features in their prospectus should be avoided for Dante applications.

Audinate has published a blacklist on its website with devices that cause problems: Networks and Switches or the PDF directly. Furthermore there are some switches mentioned on this Shure website that are NOT recommended for Dante application.

Managed Dante Switch

The big question, of course, first: is there a need for a managed switch?

Basically not for pure audio transmission at first. But there are many features that make management much easier in situations with several switches and allow the existing cable infrastructure to be used more efficiently and safely.

So now to the many catchphrases that are always mentioned in connection with switches:

VLAN

A virtual local area network (VLAN) allows the use of several separate networks on a single switch. This is advantageous for Dante applications, for example, if a separate control network is to be set up in addition to the audio network. Without VLANs, you would have to purchase a separate switch for each network and wire them to one another. Depending on the number of devices to be connected, this can actually be useful. But for a few devices per location you are much more flexible if you can use a switch twice through several VLANs.

For the connection between different rooms, for example between the FOH and the stage, several networks, i.e. VLANs, can be transmitted over a single cable, a so-called trunk.

Using VLANs, it is possible to use both the primary and the secondary Dante network on one switch and transmit them to the next switch with one cable. Although this is technically possible, two separate switches and cable connections should usually be used for reasons of redundancy. Because if a switch fails, the transmission via the other network continues if separate switches and cables are used.

QoS

The Quality of Service (QoS) technology allows the data packets to be prioritized. In the event of a bottleneck, the switch recognizes which data packets are more important and forwards them first. First the clock data is transmitted, then the audio data and only then all other data such as cute cat pictures.

In mixed networks, in which not only Dante packets are transmitted but also other information, this function can actually prevent an audio failure in the event of a sudden bottleneck.

In the professional environment, meticulous care is usually taken to ensure that the Dante switches and connections are only used for Dante devices. There are usually separate networks for transferring files between a PC and server or the Internet.

If more audio channels are transmitted over a port than possible, which can happen especially with 100Mbit ports, then QoS unfortunately doesn't help either. Because if there are permanently more than 100Mbit of audio streams, packets are swallowed. Prioritization does not help here, because in the Dante network there are almost exclusively audio packets. QoS only helps against fluctuating non-audio data.

Nonetheless, it is standard for QoS to be used in Dante networks. A switch should allow four (or more) so-called queues to be set up and the prioritization to be changed manually using the DSCP table. This means that only the packets according to the Dante specification are given priority and all other packets are sorted into the last queue. The screenshot on the right shows the configuration of a Cisco SG350 as an example.

The best remedy for port bottlenecks in Dante networks is not QoS, but more bandwidth. 1Gbit is recommended in any case, and with a high number of channels, 10Gbit between the switches.

Port Speed

1Gbit ports are currently the standard. The big question is: is it worth the extra charge for 10Gbit uplink ports? They will do no harm for sure, because in addition to more bandwidth, i.e. more audio channels that can be transmitted simultaneously, a higher speed at the ports usually also reduces the latency.

To be honest: I know a lot of theaters that “only” use 1Gbit uplinks for Dante transmissions. And so far I have not seen any urgent need to upgrade the switches to 10 Gbit in any installation. Today's usual bandwidth of 1 Gbit allows (theoretically) around 500 Dante channels at 48 kHz. Even if you halve this number because you want to run the primary and secondary network over a single line in the event of redundancy, and if we also subtract 30% of buffer so that the network can still breathe a little, we end up with around 175 channels. This is still more than enough in most homes.

However, if you are building a complex network, a certain reserve is always recommended. A few pointers to consider:

• Are usually more than 100 Dante channels in use (input signals to the mixer, signals from the mixer to the DSP, signals from the DSP to the amplifiers / speakers, possibly signals for recording)?

• are other networks / VLANs being considered besides Dante, for example networks for controlling devices, for transferring files to the server, for the Internet or for communication (intercom stations)?

• Are the Dante networks for primary and secondary built up as a common network and can both networks share uplinks in the event of an accident?

• Are several stages connected to one another, on which several teams work independently of one another?

The more questions you answered yes, the sooner you should orientate yourself towards 10Gb uplinks.

When planning a new plan, it is definitely worth investing in fiber optic cabling that also supports 10Gbit and more so that you can later use faster switches with (then perhaps the usual) 10Gbit.

Optical ports (SFP modules)

Due to the length of the cables, it is common in larger theaters that the connections between devices are made using fiber optic cables. For such a connection, the switches must have the option of an optical port. There are usually slots available for this which can be equipped with SFP modules according to the cable requirements. In Europe, multimode fiber optic cables are mostly used, but there are also houses with singlemode fiber optic cabling.

For mobile applications, it is recommended that you bring both multimode and singlemode SFP modules with you to the job so that you can use the fiber optic connections that may be available.

STP / RSTP / MSTP

The keyword spanning tree is often found in the switch feature list. And it is actually an important topic, especially in a professional environment. Because this is about redundancy in the switch cabling.

Basically, no loops may exist in an IT network. With multiple connections, data packets would always be sent in a circle and the network would become overloaded and unstable. The Spanning Tree Protocol ensures that only one connection is active and the other connections are blocked. If STP is available and active on all switches and ports, several connections can be made, for example between FOH and stage. STP selects one of them and prevents loops. And if the active connection fails, the redundant path is automatically activated and the network is fully usable again within a few seconds.

Rapid Spanning Tree Protocol (RSTP) and Multiple Spanning Tree Protocol (MSTP) are “flavours” of the original STP. As the name suggests, RSTP is faster in rebuilding the network and is the standard these days. And MSTP can be used to configure several Spanning Tree instances (which each uses RSTP) so that a different root bridge can be defined for each VLAN, in our case for the primary and secondary network. This is only necessary and useful if all switches (primary and secondary) are physically connected to one another.

In the professional theater environment, I would recommend purchasing only switches that support RSTP and MSTP.

IGMP Snooping / Querier

IGMP snooping is also heard more and more often. And it actually has its justification! When using multicast flows, the traffic for all ports inevitably increases, because the recipient sends a multicast packet to all devices in the network at the same time. Even if you only use 1Gbit switches, this can be problematic. A number of Dante devices only have a 100 Mbit port and are therefore overloaded as soon as the multicast load in the network increases (100 Mbit are reached at around 50 Dante channels).

With IGMP snooping, each switch listens to the IGMP messages and therefore knows which device wants to receive which multicast stream. This means that a Dante recipient only receives those Dante flows that it has actually ordered.

In my opinion, IGMP snooping is absolutely necessary for larger applications and is fortunately supported by most switches.

However, there are differences in the small print: not every switch that supports IGMP snooping can also function as an IGMP querier. However, exactly one querier per network is necessary. This regularly asks all hosts in the network who wants to receive which multicast stream. The other switches only listen to this traffic and distribute the multicast packets accordingly to the correct ports. Without questioning queriers, there are no IGMP messages, so nothing to listen to and the whole system does not work.

It is therefore important that at least one switch per network can work as an IGMP querier.

DHCP server

If you dial into a foreign WLAN with your mobile phone, it goes without saying that you get your IP address from a DHCP server and don't have to worry about anything else. There is then not only the IP address, but also the subnet mask and the gateway and you save a lot of typing and errors. And above all, you save yourself the trouble of asking your landlord which IP address is currently available.

There are three options for the IP addresses in Dante applications. On the one hand, you can manually enter a static IP address in each device. Second, you can activate a DHCP server on one of the switches, which assigns an IP address from an address pool to each new device. And if you don't use either of these two options, each device automatically assigns itself a link local address as an emergency solution, also known as the ZeroConf address (169.254.x.x).

The beauty of a DHCP server is that you can define a specific address range for the automatic address allocation. In a Dante Primary network 192.168.10.x you could use 192.168.10.1-200 for static IP addresses for all invariable devices like your console, your DSP and your amps. And you could let the DHCP server allocate addresses only in the range 192.168.10.201-250 for mobile devices. That way you can easily see in your Dante Controller who is new in the system.

Dante certainly works without a DHCP server. And for devices that are permanently integrated in a system, it is advisable to assign a fixed IP address anyway. In my own experience, however, it makes life easier if a DHCP server is also available in the Dante network and this takes over the configuration for mobile applications (laptops, guests) and you can start right away.

So not a must, but an advantage if at least one switch per network supports this function.

Web UI / CLI

Opinions differ as to which way of working is the better. Most of the sound colleagues prefer a web user interface, i.e. the possibility of operation via a web browser. You don't have to memorize any commands and all options are clearly displayed.

Pure IT administrators who configure switches for many hours every day, on the other hand, prefer the command line interface (CLI), because the configuration is faster than clicking through the website. Provided you have all the commands in your memory.

Most switches offer both, but unfortunately occasionally with a different range of functions. Many HP switches only have a stripped-down web interface. You have to use the command line for the full range of functions.

With the Aruba 2530, for example, VLANs can be set up and the ports assigned via the web browser. But as soon as you get to the points that are not unimportant for Dante, such as QoS or MSTP, you can no longer continue without the command line.

If you have not yet had any experience with switches and have no other experience with CLI or programming, I recommend you to get started with a switch in which all functions can be configured via the web interface.

SNMP

This function actually has nothing to do with Dante. Nevertheless, I would like to mention it, because it is used to monitor all devices and network connections, especially in larger systems.

The Simple Network Management Protocol (SNMP) enables the simple query of standard parameters. A central server can, for example, check for all switches which ports are currently active. The data rate per port can also be checked.

If you set up certain redundancies in your network using spanning tree, then you should also think about the possibility of constant monitoring. Because a redundant switch connection is of little use if it is not checked regularly.

Even if you have not yet installed such software, it does not hurt to pay attention to SNMP support for future purchases.

I have checked the support of SNMP and the mostly used parameters for Dante networks for the most common switches (Cisco, HP, Netgear, Luminex). You can find my findings in this blog article.

PoE

Nowadays, quite a few Dante devices can be supplied with power directly from the switch without a power supply unit. This function is called Power over Ethernet. Most switch series also offer models with PoE support.

This saves you a lot of work, especially in everyday mobile stage life, because you can not only leave the power supply in the cabinet, but also the power extension and Powercon adapter.

You only have to consider how much power the Dante devices require. The “old” PoE standard offers 15 watts per port, the new PoE+ gives you 25 watts.

In addition to the performance limitation per port, there is also a limit for the switch as a whole. Sometimes the same switch is available in three versions, one without PoE support, one with a small and one with a high overall PoE output capacity.

19” rack mountable

Fortunately, like the audio industry, the IT world uses 19” racks. And many switches are supplied as standard with suitable 19” mounting kits. In this respect, you can't really go wrong. There are only a few series that have their small 8-port switches meant to be used as desktop devices, not prepared for rack mounting (like the Cisco SG250 and Aruba 1930).

Fanless

I don't know about you, but I feel most comfortable when it's quiet in a control room. In this respect, it is not insignificant to check whether there are also fanless models of your desired switch series. If a switch has one or more fans, these can be quite loud and thus a nuisance. At least in the control room, but also on the stage (in the theater / opera area), attention should be paid to low noise emissions.

In most switch series, the small models (up to around 12 ports) are fanless. The larger models, especially the PoE models, usually have a fan.

The point is negligible for installation in server racks and closed amplifier rooms far away from your usual workplace.

Redundant power supply

There are the same professional versions of devices in the IT sector as there are in the audio sector. And of course there are also switches with redundant power supplies that can be exchanged during operation (hot-swappable).

This feature is usually only available in the upper league with the corresponding price. Understandably, many users will prefer to put one or two replacement devices on the shelf instead of buying a switch at 3 to 4 times the price. Because the actual features that a switch brings with it in the upper class are hardly used in everyday audio.

(c) cisco.com

Nevertheless, I would like to mention it, because a certain degree of reliability makes perfect sense, especially at the central point of a star-shaped Dante network. This applies in any case to 24/7 applications such as broadcasters. In the theater there is usually always a time window between rehearsal and performance where you can turn off the switch completely for an hour and replace the power supply. In this respect, it is understandable that redundant power supplies are rarely found in theater systems at the moment.

At Cisco there are redundant power supplies from the Catalyst 9200L*, at HP from the Aruba 2930M*.

And that's it, the most important features of a Dante switch! As you will notice when you compare the switches commonly used today, most of the features are already available in absolutely affordable models.

Last but not least, here is the already shown overview table with a few current switch models as a small summary, without guarantee:

Manufacturer	Cisco			HP / Aruba				Netgear
Type*	SG-250 CBS-250	SG-350 CBS-350	9200	1820	1930	2530	2930F	M4250
Ports	1 Gbit	1 Gbit	1 Gbit	1 Gbit	1 Gbit	100Mbit / 1Gbit	1 Gbit	1 Gbit / 2.5Gbit
Uplink-Ports	1 Gbit X: 10Gbit	1 Gbit X: 10Gbit	G: 1Gbit X: 10Gbit	1 Gbit	1 Gbit	1 Gbit	1 Gbit / 10Gbit	1 Gbit / 10Gbit
EEE deactivatable	✔	✔	✔	✔	✔	✔	✔	✔
VLAN	✔	✔	✔	✔	✔	✔	✔	✔
QoS	✔	✔	✔	-	✔	✔	✔	✔
SFP-Slots	⃘	✔	✔	⃘	⃘	⃘	✔	⃘
RSTP / MSTP	✔/✔	✔/✔	✔/✔	✔/-	✔/✔	✔/✔	✔/✔	✔/✔
IGMP Snooping	✔	✔	✔	✔	✔	✔	✔	✔
IGMP Querier	✔	✔	✔	-	-	✔	✔	✔
DHCP Server	-	✔	✔	-	-	-	✔	✔
Web-UI / CLI	✔/✔	✔/✔	(✔)/✔	✔/-	✔/-	(✔)/✔	(✔)/✔	✔/✔
SNMP	✔	✔	✔	✔	✔	✔	✔	✔
19" mountable	⃘	✔	✔	⃘	⃘	✔	✔	⃘
PoE	⃘	⃘	⃘	⃘	⃘	⃘	⃘	⃘
Fanless Models	8/8P/10P/ 18/26	10/10P/28	-	8/8P/ 24/48	8/8P/ 24/48	8P/12P	8P/12P	10
Redundant Power Supply	-	-	optional	-	-	-	-	-

✔  supported     (✔) limited range of functions
⃘   some models
- not supported

I hope I was able to provide you with a few criteria for your next Switch purchase. If you have no experience yet with switches, my recommendation would be either Cisco SG250 or SG350. I have made a detailed comparison of these in this blog post.

*Affiliate Link

Could also be interesting:

• Blog-article: Network Monitoring (PRTG) Benefits

• Blog-article: Which switches support SNMP (PRTG)?

• Blog-article: Dante Network Topologies

• Blog-article: When should I use multicast?

• Blog-article: 5 things you should know about the Dante Virtual Soundcard