On Tue, Feb 02, 2021 at 08:49:25AM -0600, George McCollister wrote: > > > > Why is it such a big deal if supervision frames have HSR/PRP tag or not? > > > > > > Because if the switch does automatic HSR/PRP tag insertion it will end > > > up in there twice. You simply can't send anything with an HSR/PRP tag > > > if this is offloaded. > > > > When exactly will your hardware push a second HSR tag when the incoming > > packet already contains one? Obviously for tagged packets coming from > > the ring it should not do that. It must be treating the CPU port special > > somehow, but I don't understand how. > > From the datasheet I linked before: > "At input the HSR tag is always removed if the port is in HSR mode. At > output a HSR tag is added if the output port is in HSR mode." > I don't see a great description of what happens internally when it's > forwarding from one redundant port to the other when in HSR (not PRP) > but perhaps it strips off the tag information, saves it and reapplies > it as it's going out? The redundant ports are in HSR mode, the CPU > facing port is not. Anyway I can tell you from using it, it does add a > second HSR tag if the CPU port sends a frame with one and the frames > going between the ring redundancy ports are forwarded with their > single tag.
So if I understand correctly, the CPU port is configured as an interlink port, which according to the standard can operate in 3 modes: 1) HSR-SAN: the traffic on the interlink is not HSR, not PRP 2) HSR-PRP: the traffic on the interlink is PRP-tagged as “A” or “B” 3) HSR-HSR the traffic on the interlink is HSR-tagged. What you are saying is equivalent to the CPU port being configured for a HSR-SAN interlink. If the CPU port was configured as HSR-HSR interlink, this change would have not been necessary. However 6.7 Allowed Port Modes of the XRS7000 datasheet you shared says: | Not every port of XRS is allowed to be configured in every mode, Table | 25 lists the allowed modes for each port. That table basically says that while any port can operate as a 'non-HSR, non-PRP' interlink, only port 3 of the XRS7004 can operate as an HSR interlink. So it is more practical to you to leave the CPU port as a normal interlink and leave the switch push the tags.
