Hello,
wrote:
What I am trying to accomplish is to have this routing-instance only route internally between other routing instances on the same switch. There is no need for routing to happen externally of the switch.
Well, to "route" You have to have packets/traffic. And how do You actually plan to "inject" traffic into this routing instance? Or do You actually plan to redirect locally-/switch-originated packets (originated from within other routing-instances or GRT on the same switch) into this routing-instance? If that's the case, I'd reckon You just need a stable/always-up interface in this instance and it does not need to be IRB. You can use loopback unit:
set interfaces lo0 unit 5 family inet address 203.0.113.1/24 set routing-instances blah instance-type virtual-router set routing-instances blah interfaces lo0.5
If the traffic is ICMP Echo Request/ping then You can go interface-less/have a "receive" route:
set routing-instances blah routing-options static route 203.0.113.0/24 receive
ICMP Echo Request packets matching this route will be answered, provided there is a route back to the source(s) of ICMP Echo Requests/pings.
HTH
Thx
Alex