Product manual

cvcccccCisco
Cisco™ CCNA : EIGRP and OSPF
Copyright © 2011 SimulationExams.com * All trademarks are duly recognised
* Best printed in landscape mode
CCNA Network Simulator CCNA Exam Simulator CCENT Exam Simulator CCNA ICND2 Exam Simulator CCNP BSCI Exam Simulator
OSPF router ID determination
1. Use the address configured by the ospf router-id command
2. Use the highest numbered IP address of a loopback
interface
3. Use the highest IP address of any physical interface
4. If no interface exists, set the router-ID to 0.0.0.0
DR and BDR Election
When two or more routers are contending to be a DR (designated Router) on a network segment, the router with the highest OSPF priority will become the DR for that
segment. The same process is repeated for the BDR. In case of a tie, the router with the highest RID will win.
OSPF Area Types
Standard Area : Default OSPF area type
Stub Area : External link (type 5) LSAs are replaced with a default route
Totally Stubby Area : Type 3, 4, and 5 LSAs are replaced with a default route
Not So Stubby Area (NSSA) : A stub area containing an ASBR; type 5 LSAs are
converted to type 7 within the area
OSPF Priority
The ip ospf priority command is
used to set manually which router
becomes the DR. The range is 0-
255 and the default is 1. 0 means it
will never be DR or BDR.
Router Types
Internal Router : All interfaces reside within the same area
Backbone Router : A router with an interface in area 0 (the backbone)
Area Border Router (ABR) : Connects two or more areas
AS Boundary Router (ASBR) : Connects to additional routing domains; typically located in
the backbone
EIGRP (Enhanced Interior Gateway Protocol)
OSPF(Open Shortest Path First)
Routing metrics used by IGRP
Bandwidth: This is represents the maximum throughput of a link.
MTU (Maximum Transmission Unit): This is the maximum message length that is acceptable to
all links on the path. The larger MTU means faster transmission of packets.
Reliability: This is a measurement of reliability of a network link. It is assigned by the
administrator or can be calculated by using protocol statistics.
Delay: This is affected by the band width and queuing delay.
Load: Load is based among many things, CPU usage, packets processed per sec
Important terms used in EIGRP
Successor: A route (or routes) selected as the primary route(s) used to
transport packets to reach destination. Note that successor entries are kept in
the routing table of the router.
Feasible successor: A route (or routes) selected as backup route(s) used
to transport packets to reach destination. Note that feasible successor entries
are kept in the topology table of a router.
DUAL (Diffusing Update Algorithm): Enhanced IGRP uses DUAL algorithm to
calculate the best route to a destination
For IGRP routing, you need to provide AS (Autonomous System) number in the command. Routers need AS number to exchange routing information.
Routers belonging to same AS exchange routing information.
OSPF and OSPF Area
OSPF is a link state technology that uses Dijkstra algorithm to compute routing
information.
An OSPF area is a collection of networks and routers that have the same area
identification.OSPF process identifier is locally significant.