Chapter 8 OSPF
8.1.3.5
8.1.3.5
8.3.1.5
8.3.1.5
Router ID
A 32-bit value expressed in dotted decimal notation (like an IPv4 address) used to uniquely identify the originating router.
3 LSR
A Type __ ___ packet is used by the receiving routers to request more information about an entry in the DBD.
link-state advertisements (LSAs)
After adjacencies are established, routers then exchange ____-____ ____.
Adjacency database
An OSPF database that creates the neighbor table.
Forwarding database
An OSPF database that creates the routing table.
Link-state database (LSDB)
An OSPF database that creates the topology table.
Backbone
Area 0 is called the ____ area.
default
As an alternative, all interfaces can be made passive using the passive-interface ____
LSR
Asks for specific link-state records from router to router
four
By default, the router Dead Interval is ____ times the Hello interval.
DBD
Checks for database snchronization between routers.
LSAck
Comfirms receipt of a link-state update packet
40 120
Dead Intervals __ seconds (default on multiaccess and point-to-point networks) __ seconds (default on NBMA networks; for example, Frame Relay)
Hello
Discovers neighbors and builds adjacencies between them
N (N - 1) / 2
Formula for # of adjacencies
10 30
Hello Packet Intervals __ seconds (default on multiaccess and point-to-point networks) __ seconds (default on non-broadcast multiple access [NBMA] networks; for example, Frame Relay)
224.0.0.5 FF02::5
Hello packets are transmitted to multicast address __.__.__.__ in IPv4 and ___ in IPv6
Router ID
ID of the originating router
(Left to Right) Data Link Frame = MAC = Destination & Source IP = Source&Destination&Protocol OSPF Packet = Type Code = RouterID & Area ID Packey Type = 01-05 = Hello,DD,LSR,LSU,LSA
Identify what is identified within each packet header?
is initialized, or when there is a change in the topology
Link-state routers flood their LSAs any time OSPF does what?
Down State
No hello packets received
Area ID
Number of the area from which the packet originated
110
OSPF has a default administrative distance of ___.
Multiarea OSPF
OSPF is implemented using multiple areas, in a hierarchal fashion. All areas must connect to the backbone area (area 0).
Database Description (DBD)
Packet Type: Contains an abbreviated list of the sending router's LSDB and is used by receiving routers to check against the local LSDB.
Hello Packet
Packet Type: Used to establish and maintain adjacency with other OSPF routers.
Link-State Request (LSR)
Receiving routers can then request more information about any entry in the DBD by sending an LSR.
LSU
Sends specfically requested link-state records
Dijkstra
The OSPF router builds the topology table using results of calculations based on the ____ algorithm.
network
The ___ command determines which interfaces participate in the routing process
1
The default priority for all OSPF routers is __
The easiest method for calculating a wildcard mask is to subtract the network subnet mask from 255.255.255.255.
The easiest method for calculating a wildcard mask is to subtract the network subnet mask from 255.255.255.255.
Smaller routing tables Refuced link-state update overhead Reduced frequency of SPF calculations
The hierarchical-topology design options with multiarea OSPF can offer what advantages?
Clearing the OSPF process
The preferred method to reset the router ID.
o to 255
The range for OSPF priority numbers?
Designated Router (DR)
The routing device configured with the highest priority is elected the __.
False (hello will initiate a two-way state)
True or False? A hello packet must be sent to initiate an establishment for a neighboring Loading State
True
True or False? Adjacent neighbors receiving the LSA immediately flood the LSA to other directly connected neighbors, until all routers in the area have all LSAs.
False
True or False? OSPF requires periodic updates.
False The router will automatically if nothing is inputted
True or False? Only the Administrator can assign Router IDs.
True
True or False? Routers in other areas receive messages regarding topology changes, but these routers only update the routing table, not rerun the SPF algorithm.
True
True or False? Routers only need to send and receive routing protocol messages with their directly connected neighbors.
False Disseminates LSAs
True or False? The DR is only used for the dissemination of LSUs.
False The Router ID is not routable
True or False? The Router ID can be found in the routing table
show ip protocols
Use the ___ ___ ___ command to verify the router ID.
Dijksta's Algorithm
Used to compute the SPF cost.
Link-State Update (LSU)
Used to reply to LSRs and to announce new information. contains seven different types of LSAs.
clear ip ospf process
What is the command to clear the router ID
LSUs contain one or more LSAs
What is the difference between LSUs and LSAs?
Down Initiate Two-way -- Exstart Exchange Loading/Full
What is the process of OSPF Operational States?
Link-State Acknowledgment (LSAck)
When an LSU is received, the router sends this back to confirm receipt of the LSU.
LSUs
___ are also used to forward OSPF routing updates, such as link changes.
an OSPF area
a group of routers that share the same link-state information
Open Shortest Path First (OSPF)
a link-state routing protocol that was developed by IETF
Intermediate System-to-Intermediate System (IS-IS)
a link-state routing protocol that was developed by ISO
Interior Gateway Protocol (IGP)
a routing protocol intended for exchanging routing information within an autonomous system
wildcard mask
a string of 32 binary digits used by the router to determine which bits of the IPv4 address to examine for a match
OSPFv2
a version of OSPF protocol that supports IPv4 only
OSPFv3 with Address Families feature
a version of OSPF protocol that supports both IPv4 and IPv6
Single-Area OSPF
all routers are in one area called the backbone area (area 0).
Shortest Path First (SPF) algorithm
also called the Dijkstra algorithm
11
an LSU packet can contain __ different types of OSPFv2 LSAs.
Dijkstra's SPF algorithm
an algorithm that is used by OSPF to process the neighbor and topology tables in order to determine the best path to forward packets
administrative distance (AD)
an indicator of the trustworthiness (or preference) of the route source. The lower the value of AD, the more trustworthiness the source has.
link-state advertisements (LSAs)
contain the state and cost of each directly connected link.
cost of an OSPF route
the accumulated cost value from one router to the destination network
Dead Interval
what is the term used for the number of seconds before declaring the neighbor router out of service?
