OSPF Flashcards
OSPF uses what protocol number for inter-router communication?
89
What are the packet types OSPF uses for inter-router communication?
- Hello
- Database description
- Link-state request
- Link-state update
- Link-state ack
True or False, the OSPF process ID must match for routers to establish a neighbor adjacency.
False
What does the Down state indicate?
Down state is the initial state of a neighbor relationship. It indicates that the router has not received any OSPF hello packets.
What does the Init state indicate?
Init state indicates that a hello packet has been received from another router, but bidirectional communication has not been established.
What does the 2-Way state indicate?
2-Way state indicates bidirectional communication has been established. If a DR or BDR is needed, the election occurs during this state.
What does the Full state indicate?
Full state indicates neighboring routers are fully adjacent.
All OSPF routers form full adjacencies with which two roles?
All routers form full adjacencies with the DR and BDR.
What is a passive interface?
A passive interface does not send out OSPF hellos and does not process any received OSPF packets.
What will happen if a Neighbor does not receive a hello from its neighbor before the dead timer interval is up?
The Neighbor adjacency will go down.
What is the first criteria for election of the DR, and the second?
The DR with the highest OSPF priority wins the election. If tied, then the router with highest RID wins.
What is a broadcast network and what links are they used for?
Broadcast networks can connect more than two devices and broadcasts sent out one interface are capable of reaching all interfaces attached to that segment. OSPF network type is set to broadcast by default on Ethernet interfaces.
What is a point-to-point network and what links are they used for?
A network circuit that allows only two devices to communicate is considered a point-to-point (P2P) network. This network type is the default for serial interfaces, GRE tunnels, and P2P Frame Relay subinterfaces. They do not use ARP.
What is a loopback network and what links are they used for?
The OSPF loopback network type states that the IP address is always advertised with a /32 prefix length even if it is not configured as that. Enabled by default on loopback interfaces.
What are area border routers and what is their purpose?
Area border routers (ABRs) are OSPF routers connected to area zero and another area. ABRs are responsible for advertising routes from one area and injecting them into a different OSPF area.
