[j-nsp] OSPF in High-Availability environments

[Jee Kay]

We have a core network of 3 Juniper M7is, all of which speak OSPF to
each other and advertise their attached subnets into OSPF.

We're trying to get this environment as fault tolerant as possible but
are running into a few problems... specifically, 'strange' behaviour
during node/link failures.

I've attached a basic diagram of the layout. Essentially, when the
primary path (labelled EES0005LON) becomes unavailable (either through
link or node failure), OSPF recovers (hello 1, dead 3) but during the
recovery the clients are disconnected from the servers with ICMP
Unreachable messages.

When designing and implementing this we were doing so in the belief
that if there are multiple paths between sites, and one path becomes
unavailable, we would have a blackhole to traffic for a maximum of the
OSPF dead time and after that everything would reroute itself.
Unfortunately because the first-hop router (MSPBCR001P on the left in
the diagram) is sending ICMP Unreachable messages after a failure of
the primary path, the failure is very visible to the clients and hence
to our customers.

Is there some particular configuration I should be using to prevent
OSPF/the router sending out these ICMP Unreachables (or are there any
'How to configure Junipers and OSPF in fault-tolerant environments'
guides)? Or is there simply no way to have seamless fault tolerance
with Junipers in our core?

Thanks in advance,
Ras