Fortigate 50E - multiple DHCPv6-PD requests with different IA_ID?
I currently have a Fortigate 50E firmware 5.6.3 connected to an AT&T residential fiber connection. They have recently rolled out dual-stack IPv6, with the expectation that the customer is to use DHCPv6-PD to obtain prefixes for their devices.
ATT forces me to use a "gateway" device in front of my Fortigate, and according to them, they have allocated a /60 to each gateway. However, the gateway does not allow you to request a /60; you must request multiple /64 subnets by issuing multiple DHCPv6 requests with different IA_ID values. Each different ID will result in a single /64 from the /60. (I will say that I have never come across an ISP that works this way; I almost think that their implementation is broken).
Is there any way to have the Fortigate do this? I have 3 internal LANs, and I'd like to have each with a different /64. I see no options in CLI under "conf system interface" -> "edit WAN" -> "config ipv6" to have multiple DHCPv6-PD requests sent.