CCNA 3 Labs and Study Guide - BINARYBB.INFO – @jagalbraith

112 Switching Basics and Intermediate Routing CCNA 3 Labs and Study Guide
Note: Now is a good time to complete Curriculum Lab 2-4: Configuring OSPF Authentication (2.3.4).
27. The DR, BDR, and every other router in an OSPF network sends out Hellos using 224.0.0.5 as the
destination address. If a DRother (a router that is not the DR) needs to send an LSA, it will send it
using 224.0.0.6 as the destination address. The DR and the BDR will receive LSAs at this address.
28. Complete the following table by listing the four types of OSPF networks and whether they have a
DR/BDR election.
Network Type Characteristics DR/BDR
Election?
Broadcast multiaccess Ethernet, Token Ring, or FDDI Yes
Non-broadcast multiaccess Frame Relay, X.25, SMDS Yes
Point-to-point PPP, HDLC No
Point-to-multipoint Configured by an administrator No
29. OSPF routers must use matching Hello intervals and Dead intervals on the same link. These are used
to time the exchange of link-state information as well as to determine when a link is down.
30. On broadcast OSPF networks, the default Hello interval is 10 seconds and the default Dead interval is
40 seconds. On nonbroadcast networks, the default Hello interval is 30 seconds and the default Dead
interval is 120 seconds.
31. These default interval values result in efficient OSPF operation and seldom need to be modified.
However, you can change them. Document the command syntax, including router prompt, to change
these values.
Router(config-if)#ip ospf hello-interval seconds
Router(config-if)#ip ospf dead-interval seconds
32. Again, refer to Figure 2-5. Assuming that the current intervals are 10 and 40, document the commands
necessary to change these intervals on the link between RTB and RTC to a value four times greater
than the current value.
RTB(config)#interface serial 0/0
RTB(config-if)#ip ospf hello-interval 40
RTB(config-if)#ip ospf dead-interval 160
RTC(config)#interface serial 0/1
RTC(config-if)#ip ospf hello-interval 40
RTC(config-if)#ip ospf dead-interval 160
Instructor Note: It is not necessary to configure the Dead interval as long as the desired interval is four times the
Hello interval. The IOS will automatically increase the Dead interval to four times the configured Hello interval.
Note: Now is a good time to complete Curriculum Lab 2-5: Configuring OSPF Timers (2.3.5).
33. Refer to Figure 2-6 for the remaining questions in this section. RTA is your gateway router because it
provides access outside the area. In OSPF terminology, RTA is called the Autonomous System
Boundary Router (ASBR) because it connects to an external routing domain that uses a different routing
policy.