The core of a network has four routers connected in a square design with Gigabit Ethernet links using /30 subnets. The network is used to carry voice traffic and other applications. Convergence time is taking more than expected. Which three actions would you take to improve OSPF convergence time? (Choose three.)
A.
Increase MTU of the interfaces to accommodate larger OSPF packets.
B.
Change the network type to point-to-point on those links.
C.
Reduce SPF initial timer.
D.
Increase hello interval to avoid adjacency flapping.
E.
Enable OSPF.
Explanation:
Point-to-point means no DR electionconvergence time for a link-state protocol is sum of the following components:
Time to detect the network failure, e.g. interface down condition.
Time to propagate the event, i.e. flood the LSA across the topology.
Time to perform SPF calculations on all routers upon reception of the new information.
Time to update the forwarding tables for all routers in the area.The OSPF Shortest Path First Throttling feature makes it possible to configure SPF scheduling in millisecond intervals and to potentially delay shortest path first (SPF) calculations during network instability. SPF is scheduled to calculate the Shortest Path Tree (SPT) when there is a change in topology. One SPF run may include multiple topology change events.
The interval at which the SPF calculations occur is chosen dynamically and is based on the frequency of topology changes in the network. The chosen interval is within the boundary of the user-specified value ranges. If network topology is unstable, SPF throttling calculates SPF scheduling intervals to be longer until topology becomes stable.
I think E simply does not make sense. If OSPF is not enabled -> no OSPF.
Of the remaining answers, increasing MTU would somewhat make sense as it would allow quicker flooding of LSAs.
No firm answer found on this though.
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As far as I remember only IS-IS tries to puts all LSA in one packet, OSPF sends them separately, so A makes no sens. But I agree E is ridiculous.
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