Hello,
I would like to suggest an additional test when reviewing Ethernet switches, especially ones that are likely to be used by home or small business users.
Does the switch being reviewed properly support mDNS/Bonjour discovery both within the local ports and also when cascaded to another switch?
There are several parts to this evaluation
The above evaluations were for a "flat" network. What if there are VLANs and/or subnets involved? This topology is often better understood because it is known that UDP broadcasts (used by mDNS/Bounjour) are not forwarded across VLANs or subnets by default, so some type of forwarding mechanism is needed.
What I have observed on a very small sample of routers/switches is that some older small-business-focused unmanaged switches don't support mDNS/Bonjour well. Also, some wifi switch/routers (even some mesh systems) have no mechanism to configure forwarding and/or snooping for mDNS/Bonjour to allow a cascaded switch to contain a discoverable device. Some of these wifi switch/routers support forwarding and iGMP snooping, but for only IPTV multicast streams, not the general cases needed for mDNS/Bonjour for a cascaded switch.
This is a two sided issue, and both sides of the cascaded switches need to do their part properly.
In my case, I found a great deal on an older 48 x 1Gbit port unmanaged HP switch (an Aruba Network relabled switch). Firmware for the 24-port and smaller switches was updated in 2020 for better mDNS/Bonjour support, but the 48-port version was not. If my network printer (discoveralble by mDNS/Bonjour) was connected to this older switch cascaded to my wifi switch/router, my moble phones and tablets could not discover the printer. Move the printer to a direct connection on the wifi switch/router and the printer was discoverable from the mobile devices.
I would like to suggest an additional test when reviewing Ethernet switches, especially ones that are likely to be used by home or small business users.
Does the switch being reviewed properly support mDNS/Bonjour discovery both within the local ports and also when cascaded to another switch?
There are several parts to this evaluation
- The mDNS discoverable device (such as a network printer) is directly connected to the switch being reviewed and is discoverable by a client also directly connected to the same switch. This is the easiest condition.
- Cascade a second switch to the switch being reviewed in a "flat" network (no subnet, no VLAN). Attach a client to the cascaded switch. Can the client on the cascaded switch discover the mDNS device properly? This requires that the primary switch under review properly forward the UDP broadcast packets used by mDNS/Bonjour to the cascaded switch. Does this work? What, if any special configuration is needed on the switch being reviewed or the cascaded switch with the client connected?
- This is often related to a mobile device trying to access a network printer, even if the network printer has a fixed address. Often, the default for the mobile device is to use mDNS/Bonjour to discover the network printer, and it can be difficult to force the client software to use a fixed IP for the printer. Windows and Linux systems can be straightforwardly configured to use a fixed known IP address (or local DNS lookup) for the printer and do not use mDNS/Bonjour.
The above evaluations were for a "flat" network. What if there are VLANs and/or subnets involved? This topology is often better understood because it is known that UDP broadcasts (used by mDNS/Bounjour) are not forwarded across VLANs or subnets by default, so some type of forwarding mechanism is needed.
What I have observed on a very small sample of routers/switches is that some older small-business-focused unmanaged switches don't support mDNS/Bonjour well. Also, some wifi switch/routers (even some mesh systems) have no mechanism to configure forwarding and/or snooping for mDNS/Bonjour to allow a cascaded switch to contain a discoverable device. Some of these wifi switch/routers support forwarding and iGMP snooping, but for only IPTV multicast streams, not the general cases needed for mDNS/Bonjour for a cascaded switch.
This is a two sided issue, and both sides of the cascaded switches need to do their part properly.
In my case, I found a great deal on an older 48 x 1Gbit port unmanaged HP switch (an Aruba Network relabled switch). Firmware for the 24-port and smaller switches was updated in 2020 for better mDNS/Bonjour support, but the 48-port version was not. If my network printer (discoveralble by mDNS/Bonjour) was connected to this older switch cascaded to my wifi switch/router, my moble phones and tablets could not discover the printer. Move the printer to a direct connection on the wifi switch/router and the printer was discoverable from the mobile devices.