6. OSPF Packet Types Flashcards
What are the 5 OSPF packet types
- Hello
- Database description
- Link-state request
- Link-state update
- Link-state acknowledgement
What is communicated in the hello packet?
- Network/subnet
- Hello interval (must match)
- Options
- Router priority
- Router dead interval (must match)
- DR/BDR
- Neighbor (RID)
What are the hello packets used for?
- To ensure that two-way communication exists
- Serves as a failure detection
What is the TTL of a Hello packet?
1
What are the Hello timers?
Broadcast 10-40 Non-Broadcast 30-120 P2P 10-40 P2MP 30-120 P2P-MP Non-Broadcast 30-120
What is the difference between broadcast and non broadcast hello packets?
Non-broadcast hello will only be sent after a neighbor statement has been used
What is the destination of the Hello packets?
224.0.0.5
What is communicated in the database description packet?
- MTU (must match)
- Options
- DBD bits
- DBD sequence number
- LSA headers
Which node becomes the master in the master/slave election in the DBD packet?
The node with the highest RID. The master increments the sequence number
What is communicated in the link-state request packet?
- Type of LSA requested (type of LSA)
- The link-state ID
- The RID of the router responsible for originating the LSA
Where is the link-state request used for?
Used to request missing LSA information for LSAs seen during the DBD packet exchange.
What does the link-state ID represent in the link-state request packet?
For type 1 the RID, for type 2 the DR IP
What is communicated in the link-state update packet?
The full LSAs
Where is the link-state update packet used for?
Used to perform flooding. If no LSAck is received it will resend every 5 seconds
What is communicated in the link-state acknowledgement packet?
Only the LSA header information of the LSA(s) which are being acknowledged
