Voice vlan IPv6 addresses appearing on PC on T48S

[danzoom]

Hello,

Yealink T48s with computers on the PC port.

WAN port vlan is configured - vlan contains phones and the voice router (Cisco 2911).

PC port vlan is configured.

Switches are a mix of Cisco 9300, Dell PowerConnect 6248, and a ubiquiti.

Both the phone and the PC are getting IPv6 addresses from the voice router.

The "Span to PC port" option is off.

I have had to disable IPv6 on the voice router. The computers connected to T48s were having IPv6 connectivity issues.

I don't know how to telnet/ssh in to a Yealink phone, so I'm unable to understand how Yealink is bridging the "WAN" and PC ports.

However, computers are NOT getting IPv4 DHCP ip addresses from the voice network. Only IPv6 addresses from neighbor discovery.

Is anyone able to shed some light on this odd behaviour?

Cheers