IPv6 Virt Addys not being discovered

I'm having a bit of an argument with my IT department. They are saying my problem is the config on my F5 and I'm thinking they are missing something on the next hop router.

The long and short is that IPv6 virtual addresses added on my F5 BigIP LTM cannot be reached outside the local network.

...unless the next hop first pings those virtual addys.

Tried versions: 11.5.4, 12.1.2, 12.1.5 - across 2 systems: a 5xxx series and a VE on a VM.

Here's the [extremely trimmed down] setup:

    D

      |

   Rtr

  __|__

 /       \

A         B

          |

          C

Rtr = Next Hop = a:b:c::1

A = Test PC = a:b:c::2

B = F5 = VirtIP6 = a:b:c::3 & Internal = fc00::1

C = Target PC = fc00::2

D = Test PC = e:f:g::2

In short:

• A can reach C by way of the virt addy on B
• C can reach A and D
• D can reach A
• D cannot reach B or, of course, C

(*reach = ping6 and ssh)

However, if the Rtr pings B, then D >CAN< get to C by way of the virt addy on B

...until the ‘learned’ B address expires on the Rtr, then things go back to where D cannot see B/C

Might also help to mention that the IPv4 side of all of the above works great and has been for years.

Any thoughts would be appreciated.