Thursday, May 9, 2013

OSPF Problem 5

Try to solve the lab problem in 10 minutes or less.

  • Configure OSPF area 0 on Ser0/0 of R1, and R2 using default OSPF mode of operation.
  • Enable OSPF area 0 on R3‘s Ser0/0.123 sub-interface and its Loopback0 interface.
  • Ensure there is full reachability and full adjacency in Frame-Relay network configured.
  • Ensure R3 can ping (R1′s Loopback0) sourced by its Loopback0 interface.


Extra Credit
Take as much time as you need to answer the following questions:
  1. What is the default OSPF mode used on NBMA (non-broadcast, multi-access interfaces) links?
  2. What is/are compatible OSPF modes with the default mode used on NBMA links?
  3. What would you configure to make other OSPF mode to be compatible with NBMA?
  4. What are the default timers (hello/dead) used on NBMA links?
  5. How are OSPF neighbors discovered on NBMA links?
  6. Which OSPF routing context command is required for the routers to establish OSPF communication?
  7. What is going to happen if an OSPF router receives a unicast addressed ‘hello’ packet from its OSPF neighbor?
  8. What OSPF router roles does NBMA network elect?
  9. Which command shows the role of the router on a specific NBMA link?
  10. In case of hub-and-spoke NBMA topology, what OSPF role should spoke routers take (justify your answer)?
  11. What are the two ways of configuring the required role in a spoke router in NBMA hub-and-spoke topology?
  12. What is OSPF next-hop behavior on NBMA links in a hub-and-spoke topology? What do you need to take care of regarding next-hop?
  13. In case of non-broadcast OSPF mode, what does LSDB show as far as the following are concerned (assuming default ospf mode): link connected to, link id, link data?

When you have solved the problem check the hint(s) below:

Lab Hint
  • Can R3 reach R1‘s Ser0/0 with the default configuration (before you have introduced changes)?
  • What NBMA role should the spokes (R1 and R3) play in this configuration?
  • Does R3 use address as its next-hop towards
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