Pathway IGMP Primer User manual

Brand: Pathway

Model: IGMP Primer

Type: User manual

Why IGMP?

Internet Group Management Protocol (IGMP) allows switches to do what switches do best: get

the right trac to the right desnaon eciently and ‘switch’ trac away from those that don’t

need it. Although there are many devices and protocols that keep the Internet running, IGMP

can be seen as one tool to migate overburdening any one node. Without clever hardware like

routers and switches and open standards like IGMP, all the trac on the Internet would hit your

PC’s network card all the me. It’d crash for sure! Some entertainment protocols like Dante rely

on IGMP and others, like sACN, certainly can make good use of it, especially in larger systems. If

your system has more than one console or more than 20 universes of sACN, you’d do well to

educate yourself on what IGMP does and see if it makes sense to use it.

Background

IGMP allows for packet ltering and forwarding by the switch based on mulcast groups.

Mulcast trac is dened as packets with the desnaon addresses in the range of 224.0.0.0 to

239.255.255.255.

sACN is a mulcast protocol where its desnaon IP is dened by the streaming universe in the

range of 239.255.y.x, where x is the least signicant byte and y is the most signicant byte of the

16-bit universe number. For example 239.255.0.1 is sACN universe 1 and 239.255.1.1 is sACN

universe 257. Networks using sACN can take full advantage of IGMP by reducing the trac on

the link to the gateway to just the Network DMX Universes the gateway is congured to receive.

There are other entertainment protocols, such as Dante by Audinate, that require IGMP.

Note that apart from sACN (and Pathway ssACN) which both use mulcast address in the range

of 239.255.y.x, all Pathway Connecvity devices adverse they are alive and on the network by

chirping on mulcast 239.255.237.2. If you have IGMP miscongured, you may not see all

devices in Pathscape, even if you can ping them directly by their IP. (Ping is unicast). If you see

some devices on the switch local to you, but the rest of the rig connected to other switches, try

turning on IGMP Snooping and the Querier on the local switch. If more devices appear, it’s likely

the other switches have Snooping turned on and couldn’t nd a Querier.

To learn more about how IGMP works, watch this video.

hps://youtu.be/0MVE22JCIt4?si=7I_0X_PzFDlSsOiG

If your network has Layer 3 roung and is managed by an IT department, make sure the router is set up as the

Querier and not the VIAs.

IGMP Primer

IGMP Primer – November 2023

Page 2 of 8

The Mechanics

There are two mechanisms needed for IGMP to work properly:

1. First, each and every switch on the LAN (or VLAN, as is necessary when using Pathway’s

VIA switches) must enable IGMP Snooping. This means, rather than just broadcasng

the mulcast trac that comes into the switch to every other port, the switch will

actually read part of the mulcast packet, digest it and decide where it goes. This

happens VERY quickly – we call it ‘wire-speed’. The data is not routed into the

management processor to do this; it happens in the Layer 2+ switch fabric. This is one of

the reasons you have paid for a managed switch!

2. At least one switch needs to be “in charge”. It is known as the Querier. It asks who is

interested in mulcast groups and listens for end-devices wanng to join or leave said

groups. In a Pathway network, this is equivalent to a 2-Port Pathport saying that it’s

interested in, say, Univ1 and Univ2

†

. The Snooping switches listen to (or snoops on) this

conversaon and registers the port that the device is connected to. Then if it sees trac

desne for 239.255.0.1 or 239.255.0.2, it send it on, through as many switches and as

many ports needed to connect the source of the sACN to the Pathport. It also sends the

sACN to the Querier.

In pracce, it’s always good to make the Querier a switch that is likely to have the most up-me

and close to the source of the sACN. i.e., the one in the booth that is on a UPS. Choose one with

gigabit or beer capabilies as it will see all sACN trac on your network.

‡

You should also have

an addional Querier as a backup. It maers not which two VIAs you choose or what their IP

addresses are; there is a background elecon process and they will gure it out among

themselves.

Depending on the vintage of the Pathway Connecvity device, some navely use IGMPv2 and

others IGMPv3. Version 3 Querying is backward compable to v2 by design, but be aware, some

third party switches have advanced Querier opons to explicitly exclude the use of IGMPv2. This

opon can almost always be disabled to allow maximum compability.

Pathscape Setup for IGMP

1. VLANs must be enabled for every switch on the network – even if you’re not going to

use more than one VLAN on your network.

a. Select VLAN Cong tab

b. Press VLAN Global Properes

c. Change from VLAN Names to Advanced Properes

d. Change VLAN Support to Enabled

†

By the way, a single port Pathport can listen to a lot more than a single sACN universe. With custom patches, each

of the 512 slots can subscribe to eight dierent universes at once. So don’t be surprised if a 1-Port Pathport

subscribes to mulple IGMP Groups.

‡

1GB links can support 4000 universes of sACN. Whereas 100MB links saturate with about 400 acve universes.

10GB links support upward of 40,000 universes.

IGMP Primer – November 2023

Page 3 of 8

e. A sensible range is 1 through 10. The more you use, the slower the boot process.

Pracce shows that anything over 30 is excessive.

f. It’s normal to keep the Management VLAN on VLAN 1. The VIA port your Pathscape

laptop is connected to must be on the Management VLAN or you won’t be able to

manage the VIAs.

2. If you want, name your VLANs. This is normally done by department. Just keep in mind,

a VLAN is a Virtual Local Area Network. One device on VLAN1 will never see another

device on VLAN2.

3. While staying in the VLAN Cong tab, expand the VLAN you want to enable IGMP on:

It is valid to put other lighng gear and even Pathway Connecvity devices like Pathports on other VLANs. Just be

sure to congure your laptop’s connecon port on the VIA closest to you to be on the right VLAN to see them. And

keep in mind, if you plug Pathscape into a port on a dierent VLAN you won’t be able to any see any of the VIAs on

the Management VLAN (it’s a dierent LAN).

IGMP Primer – November 2023

Page 4 of 8

4. Choose the primary VIA and turn on Querier and Snooping.

5. Choose one other VIA on this VLAN and enable both Snooping and Querier to congure

the backup Querier.

6. Go to every other VIA on this VLAN (shi or control click for mul select) and turn on

Snooping only:

7. Repeat for other VLANs as necessary.

IGMP Primer – November 2023

Page 5 of 8

Front Panel Setup of IGMP per VLAN

This is what an idle VIA’s display will look like. Press in the encoder to go to the main menu.

Scroll to “Advanced Sengs” and push to enter.

Enabled VLAN support by pressing the encoder and selecng ENABLE. Note, the next menu

opon “VLAN Setup” will not be shown if VLANs are not enabled. It is recommended to use

Pathscape to setup VLANs for two reasons: 1) The Pathscape Global VLAN properes makes

sure every VIA gets the same sengs, and 2) Only with Pathscape can you name the VLANs.

IGMP Primer – November 2023

Page 6 of 8

Scroll to VLAN Cong / Status and push to enter.

Choose your VLAN. My main VLAN1, labeled “Shock”, is both my management VLAN for the

VIAs and where all my other Pathway Connecvity gear lives. Other VLANs have other purposes.

Push the encoder to congure the selected VLAN. Remember, IGMP is per VLAN.

Scroll to IGMP Snooping and push to enter.

IGMP Primer – November 2023

Page 7 of 8

Click to change Disabled to Enabled, push, the scroll to < Back > and push.

Note the menu has now changed. Once Snooping is enabled, you may, if you wish, make this

switch a Querier. Push to change, scroll to “Enable” push, scroll to <Back> and push.

Enable the Querier on two switches, preferably both on a UPS and in dierent physical

locaons. Only one will be used. The system will automacally elect one. At present, there is no

way to know which VIA is the acve Querier.

On any switch that is Snooping, you can list the current mulcast groups this switch will pass.

This screen shot shows the menu opon under the VLAN setup, in this case Shock(1). You can

IGMP Primer – November 2023

Page 8 of 8

also scroll to an individual port and see specically the subscribed groups for that port alone.

This screen show shows sACN universe 19, 24 and 66 will ow through this VLAN (or port,

depending on which menu item chosen). When viewing the VLAN Status | Current Mulcast

Groups, clicking on an item in the list will show which ports on this switch are subscribed to that

group.

As of Pathscape v4, the reporng of mulcast groups is ONLY available on the front display.

Pathway IGMP Primer User manual

Pathway IGMP Primer User manual

Pathway IGMP Primer User manual

Related papers

Other documents