Hello
I work in the development of professional audio networking solutions. Our modules run embedded firmware using a real time OS.
From the point of view of the switch, there's no difference between our devices and a regular computer with a standard OS, with the exception of boot time and the delay between Ethernet Link-Up and the first packet being issued by the interface.
This is the description of the issue:
- We use IGMP snooping in the switch, version 2
- Our hardware boots and powers its own Ethernet interface
- Some milliseconds later, the first IGMP "subscriptions" are sent out, as the device wants to receive for example PTPv2 packets (224.0.1.129)
- The switch ignores the subscriptions, and the device does not receive any of the subscribed packets
- Seconds later, whenever it was due, the IGMP querier refreshes the snooping and traffic starts normally
It seems that the switch is not ready to store IGMP subscriptions into the snooper for a short time after the link is up for a port.
Here's some additional information:
- Subscriptions that are issued later do not show this problem
- The subscription packets are correctly received by the switch, as I can see them using a mirror port; they are just not taken into account for the snooper
- A workaround for the issue is, of course, to force static forwarding on all ports for 224.0.1.129.
- I am using a Cisco SG-300-10, firmware 1.4.7.6
- I was able to reproduce the problem also on a SG-200-08, firmware 1.0.8.3, and the workaround doesn't work on this one because it doesn't accept the static forwarding configuration (just opens a blank pop-up when I try)
I believe this is a bug, but I don't know where to report it besides this forum.
I hope I have described the problem sufficiently. Please let me know if more information is needed.
Thanks, and kind regards,
Roberto.
