PPPoE fails on em1, works on em2

[ilumos]

Hi there,

I was running 24.7, with:

• Lenovo m720q
• HP NC364T Quad copper NIC, em0, em1, em2, em3
• em0 assigned to LAN
• pppoe0 assigned to WAN
• pppoe0 using em1 as parent interface

Today I upgraded to 25.7 and the PPPoE connection did not come up, with logs showing "ppp [wan_link0] PPPoE connection timeout after 9 seconds".

After failing to resolve the issue, I assumed my configuration and/or installation was corrupt, so I erased the storage, installed 25.7 fresh, assigned interfaces and configured PPPoE as above, performed no other configuration, and still get the same error logs and no PPPoE connection.

The only way I can get PPPoE to connect successfully is to change the parent interface of pppoe0 to em2. Even more strangely, setting the parent interface to em3 also prevenets the PPPoE conenction from being established.

I found another thread from someone experiencing the same issue:
https://forum.opnsense.org/index.php?topic=39074.0

So strange - what is going on?

Thanks!