CCNA IP Routing Flashcards
What is the administrative distance of OSPF?
110
What is the administrative distance of a directly connected route?
0
What is the administrative distance of a static route?
1
What is the administrative distance of BGP external routes?
20
What is the administrative distance of EIGRP?
90
What is the administrative distance of BGP internal routes?
200
What is the administrative distance of RIP?
120
Where does a router store all the OSPF LSAs it knows about?
The Link State Database (LSDB)
In OSPF, what is the default LSA aging timer?
30 minutes
To what multicast address are OSPF Hello messages sent?
224.0.0.5
If two OSPF neighbors are in “2-way” state, what has happened? What has NOT happened?
Both routers see each other’s RID and their parameters match. They have not yet exchanged LSAs.
An OSPF LSA is sent in what type of packet?
LSU (Link State Update)
If a router is missing an LSA from its neighbor, what does it send?
A Link-State Request packet
In OSPF, what does a “full” state represent?
Two neighbors have exchanged all known LSAs.
What is the OSPF “All SPF DRs” multicast address?
224.0.0.6
In what condition is “2-way” the normal end state for OSPF neighbors?
When they’re non-DR or non-BDR on a given LAN. They won’t exchange full databases with other non-DR routers, just with the DR and BDR.
In OSPF, what is the difference between a “neighbor” and a “fully adjacent neighbor”?
A neighbor will be in a 2-way state; an adjacent or fully adjacent neighbor will be in a Full state.
List three types of OSPF LSAs.
1) Router LSA
2) Network LSA (on networks with a DR)
3) Summary LSA (from other areas)
To determine the OSPF router ID, the router will by default choose…
The highest working loopback address, followed by the highest working interface (non-loopback) address
What show command will display the router’s post-Dykstra, pre-routing table SPF calculation results?
show ip ospf rib
After the OSPF process has run Dykstra, what determines if a route gets put into the routing table?
The administrative distance - if the router knows about a route from a “better” source, it will use that over the OSPF route.
The OSPF process can be stopped and restarted with what command?
clear ip ospf process
OSPF interface costs can be manually set between what two values?
1 and 65,535
What command sets a global baseline for OSPF interface cost based on speed?
auto-cost reference-bandwidth
By default, how many equal-cost paths can OSPF put into the routing table for one route?
4 (although apparently this varies depending on router platform?)
What command changes the maximum number of equal-cost paths OSPF can put into the routing table?
maximum-paths <number></number>
The OSPF router with the (highest/lowest) priority will win the DR election. If priorities are equal, the router with the (highest/lowest) RID will win.
highest, highest
What does the OSPF dead timer do?
Tells the router how long to wait before believing a neighbor has failed (usually 4x the hello timer, 40s by default)
What is the default OSPF Hello timer?
10s
If a pair of OSPF routers are configured with Broadcast on one side and Point-to-Point on the other, what happens?
The routers form a full neighbor relationship, exchange LSAs, but do not put the routes in their routing tables.
