Add on, I now have the answer that I could not give earlier.
We will be supplying a device on a customer site and issuing a /30 from our pool we have available. So, it kind of answers my own question now:
IP Address at customer site, talktalk should just create a .1q trunk to our interface where we will create the subinterfaces with the second available address within that /30 supplied. So, now my quesiton is, do I configure the interfaces as follows:
set interface xe-1/0/0 vlan tagging
set interface xe-1/0/0 unit 15 vlan-id 15 family inet address xxx.xxx.xxx.xxx
set interface xe-1/0/0 unit 30 vlan-id 30 family inet address xxx.xxx.xxx.xxx
I am expecting, as the core router is a layer 3 device, that it will strip the vlan-id automatically and forward out of the interface for the internet address required....?
So, I expect the route to be the following:
Customer --> Core 1 --> DNS --> Core 1 --> customer --> core 1 --> Upstream peer ASN --> Internet