CIT 167 Chap 8 OSPF Part 1

Question 1

what is a router ID ?

Answer 1

an ID chosen by the admin. or automatically to identify the router when using the OSPF protocol.

Question 2

how is a router ID automatically chosen? (if not admin. chosen).

Answer 2

if a loopback ipv4 is configured then the highest one is chosen otherwise, the highest ipv4 address configured on router is used.

Question 3

what does a router ID look like?

Answer 3

looks like an ipv4 address, but is not routable. ex: 1.1.1.1

Question 4

if a new router id is configured what must be done to the router and why?

Answer 4

it must be reloaded b/c the neighbor routers will need to update their tables.

Question 5

what is a Wildcard mask?

Answer 5

OSPF uses the network address and wildcard mask to enable ospf on interfaces. the wildcard mask is the inverse of the subnet mask on that interface.

Question 6

what area id number is set when the ospf is: single-area ospf?

Answer 6

zero (0)

Question 7

what is a passive interface and why use it?

Answer 7

a passive interface is an interface that will not send OSPF updates to connected devices. this is used when the other end of the connection is not an OSPF enabled router and therefore does not need the router updates. this is used to prevent wasted resources/ bandwidth and for security.

Question 8

for ospfv2 is unicast routing enabled by default?

Answer 8

yes

Question 9

which version(s) of OSPF uses ipsec authentication?

Answer 9

OSPFv3

Question 10

which version(s) of OSPF uses link-state routing protocol?

Answer 10

both

Question 11

which version(s) of OSPF uses dynamic routing protocol?

Answer 11

both

Question 12

which version(s) of OSPF uses cost as a metric?

Answer 12

both

Question 13

which version(s) of OSPF uses FF02::6 for DR and BDR multicasts?

Answer 13

OSPFv3

Question 14

which version(s) of OSPF uses 224.0.0.6 for DR and BDR multicasts?

Answer 14

OSPFv2

Question 15

what does FE80 represent?

Answer 15

this is the ipv6 link-local address. *the link local address is the address used to communicate OSPF between routers on the same link.

Question 16

link local address?

Answer 16

This is the router id on an ipv6 using OSPF. the link-local address allow routing communication to take place between OSPFv3 routers that are connected to the same link (subnet) and no other routers get that info. *the link-local address is used for routing protocol messages.

Question 17

what is the link local prefix address?

Answer 17

FE80 - FEBF. u see the FE80 the most often.

Question 18

does the ospfv3 Process ID need to match the neighbor routers? why?

Answer 18

no, b/c the process ID is the same as the Router ID and is only relevant to the local device.

Question 19

what is the OSPFv2/v3 Process ID?

Answer 19

a number between 1-65k that represents that particular router. only relevant to that local router and can be the same or diff. number than neighbor routers.

Question 20

what command is used to enable OSPFv3 on an interface (IPV6)?

Answer 20

ipv6 OSPF ‘process-id’ area ‘area-id’

• the process-id is the id of the process used and was configured with the following command: ipv6 router ospf ‘process-id’