Here's my test topo:
Here's my node 4 config: (cost = 50 was just the last cost I set on the link to node 5)
[admin@Mikrotik-4] /routing ospf interface> /export compact
# apr/01/2015 19:24:10 by RouterOS 6.27
/ip neighbor discovery
set ether1 discover=no
/routing ospf instance
set [ find default=yes ] router-id=126.96.36.199
add address=10.1.1.4/24 interface=ether1 network=10.1.1.0
add address=188.8.131.52/32 interface=lo1 network=184.108.40.206
add address=10.0.34.4/24 interface=ether2 network=10.0.34.0
add address=10.0.45.4/24 interface=ether5 network=10.0.45.0
add address=10.4.0.1/24 interface=ether3 network=10.4.0.0
/ip route vrf
add interfaces=ether1 routing-mark=mgmt
/routing ospf interface
add cost=50 interface=ether5 network-type=point-to-point
/routing ospf network
Would you call this a fair representation?
(not shown = a single 10.x.0.1/24 on each router as a "customer" interface)
(Also - for some reason, internally, GNS3 swapped ether3 and ether5 on tik 4 so ether5 -> node5 on node 4, the drawing label is incorrect)
When I change the cost of the interface on router D, router E shows:
echo: route,ospf,info OSPFv2 neighbor 220.127.116.11: state change from Full to Init
(and sadly, there's no info-level loging event when the state changes Init -> Full)
Debug level shows all of the LSA flooding and route changing, etc. that you would expect, and indeed, the uptime on the adjacency does reset. (Tested simpler topo in Cisco - adjacency doesn't reset, just sends a LS-Update)
During the change, I ran a constant ping from 18.104.22.168 to 22.214.171.124 - Even running this in GNS3, I only dropped one ping (due to TTL exceeded @ node 5) during the re-converge, but it didn't take a neighbor timeout. This behavior was the same for broadcast and point-to-point network types. Granted, I didn't stuff the routing table full of routes, which might take slightly longer if more LSAs have to be sent/updated. You did say that convergence is fast once the other side times out....
I must still have something different because the route never gets torn down completely (which would cause the unreachable). It just switches direction around the ring, and if a node between the propagating topo-change LSA updates happens to send the old way, then the packet bounces back and forth between the two routers that disagree.
(which is why I got TTL expired as my single ping that fails)
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