The "Foundation Summary" section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on your exam, a well-prepared candidate should, at a minimum, know all the details in each "Foundation Summary" before going to take the exam.
Table 1-8 shows the metrics used by the IP routing protocols.
Table 1-8. Routing Protocol Metrics
Routing Protocol
Metric
RIPv1
Hop count
RIPv2
Hop count
IGRP
Bandwidth, delay, load, reliability
EIGRP
Bandwidth, delay, load, reliability
OSPF
Cost (The Cisco default states that the cost of an interface is inversely proportional to the bandwidth of that interface. A higher bandwidth indicates a lower cost.)
IS-IS
Cost
Table 1-9 explains how to read the information in the routing table, as explained in the show ip route command.
Table 1-9. Explanation of the show ip route Command
Code
Protocol That Derived the Route
I
IGRP
D
EIGRP
D EX
External EIGRP
R
RIP
C
Directly Connected
S
Static
E
EGP
B
BGP
i
IS-IS
I L1
IS-IS level 1
I L2
IS-IS level 2
M
Mobile
U
Per- user static route
o
ODR
T
Traffic-engineered route
O
OSPF networks from within the same area as the router. These are networks learned from router and network LSAs.
O IA
OSPF interarea. This is sent out by the ABRs and is created from the summary link LSA (type 3 and type 4). These routes will not be seen on a router within a totally stubby area because it will not receive LSAs external to the area.
O N1
OSPF NSSA external type 1
O N2
OSPF NSSA external type 2
O E1
OSPF external type 1. These routes are generated by the ASBR and show routes that are external to the autonomous system. The cost of this external route is the summarization of the external cost, plus the cost of the path to the ASBR. These routes will not be seen in a stub or totally stubby area.
O E2
OSPF external type 2. These routes do not take into account the cost of the path to the ASBR. They consider only the external cost.
