This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.
Question:
I have configured a port on the botblox industrial to be:
- no autonegotiation
- 100 Mbps / full duplex
I also configured the ports to only advertise the 0x04 (100/full) config and saved the configuration to ensure that those persist on power cycle. Then I powered-on our system and ran the port # phy show command to confirm the speed/duplex that each port was setup as and noticed the following. Is it possible for a link to report 10/full if the advertised modes do not include 10/full?
Answer:
Yes, I believe this can happen on the SwitchBlox Industrial.
When auto-negotiation is disabled, the advertised-mode setting is effectively no longer involved in determining the link speed — the PHY is operating from the forced speed/duplex configuration instead.
There is also a power-saving feature in the IP175G PHY called WOL+ down-speed. This can temporarily reduce a 100 Mbps link to 10 Mbps when the port is idle, and the feature is enabled by default.
That would explain why phy show can report 10/full even though 10/full is not included in the advertised modes.
So in this case I don’t think the PHY has actually negotiated an unadvertised 10/full mode; I suspect you’re seeing the WOL+ down-speed behaviour.
If you need the port to remain strictly at 100/full at all times, we should disable the WOL+ down-speed function as well.