NETW204: Assignment 4, Link-state Routing and OSPF (50 points)

Fill in the blanks below with either the term defined or the definition for the terms listed. Each answer is worth 2 points each, 25 questions X 2 = 50 total points. Type answers in the appropriate cell; text will automatically wrap. Post your completed assignment to the dropbox.

NAME

Term Definition

1 area border router (ABR) Attaches to multiple areas, maintains separate link-state databases for each area it is connected to, and routes traffic destined for or arriving from other areas

2 Autonomous System

Boundary Router (ASBR) the router located between an OSPF routing domain and a non-OSPF network

3 Backup Designated Router (BDR) A router that becomes the designated router if the current designated router fails. The BDR is the OSPF router with the second-highest priority at the time of the last DR election.

4 database description (DBD) Contains an abbreviated list of the sending router’s link-state database and is used by receiving routers to check against the local linkstate database

5 Designated Router (DR) OSPF router that generates LSAs for a multiaccess network and has other special responsibilities in running OSPF.

6 DRothers Routers that are not a DR or BDR. They are the other routers in the OSPF network.

7 Flapping link Routing problem where an advertised route between two nodes alternates (flaps) back and forth between two paths because of a network problem that causes intermittent interface failures.

8 Backup Designated Router (BDR) Router ID for an OSPF router if no loopbacks are configured?

9 link-state acknowledgment (LSAck) Acknowledges receipt of LSA (link-state advertisement) packets. Link-state acknowledgment packets are Type 5 OSPF packets.

10 link-state advertisements (LSA) Broadcast packet used by link-state protocols that contains information about neighbors and path costs. LSAs are used by the receiving routers to maintain their routing tables.

11 link-state request (LSR). Asks for more information about any entry in the

DBD

12 link-state update (LSU) Link-state update packets are Type 4 OSPF packets. A link-state update packet carries a collection of link-state advertisements one hop farther from its origin.

13 Open Shortest Path First (OSPF) Link-state, hierarchical IGP routing algorithm proposed as a successor to RIP in the Internet community. OSPF features include least-cost routing, multipath routing, and load balancing. OSPF was derived from an early version of the ISIS Protocol.

14 priorities When this is not equal, the router with the highest number will be the DR regardless of router ID values

15 RFC 2328 OSPF Version 2

OSPF Commands: Describe the results you would get from entering the commands below and how the results might be used by a network engineer.

Command Description

16 Router(config)# router ospf 123 Starts OSPF process 123.

17 Router(config-router)# network 172.16.10.0

0.0.0.255 area 0 OSPF advertises interfaces, not networks. Uses the wildcard mask to determine which itnerfaces to advertise. Read this line to say “Any interface with an address of 172.16.10.x is to be put into area 0.”

18 Router(config-if)# ip ospf priority 50 Changes the OSPF interface priority to 50.

19 Router(config-if)# bandwidth 128 If you change the bandwidth, OSPF recalculates the cost of the link

20 Router(config-if)# ip ospf cost 1564 Changes the cost to a value of 1564

21 Router(config-if)# ip ospf hello-interval 20 Changes the Hello Interval timer to 20 seconds.

22 Router# show ip ospf To display general information about OSPF routing processes

23 Router# show ip ospf neighbor lists all ospf neighbors and their states

24 Router# show ip ospf neighbor detail displays a detailed list of neighbors

25 Router# show ip ospf interface Displays OSPF info as it relates to all interfaces

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