Layer 3 Technologies - OSPF (v2 and v3) - Implement and troubleshoot neighbor relationship
16 important questions on Layer 3 Technologies - OSPF (v2 and v3) - Implement and troubleshoot neighbor relationship
What are the OSPF neighbor states? 8
-Attempt (unicast, NBMA environment)
-Init (multicast)
-Two-way
-Exstart
-Exchange
-loading
-full
What does the OSFP state down mean?
-But hello packets can still be sent to the neighbor
What does the OSFP state attempt mean?
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What does the OSPF state 2-way mean?
A Hello has been received from the neighbor, and it has the receiving router’s RID in it. This is a stable state for pairs of DROther neighbors.
Router recieving hello packet sees its own router ID within the recieved hello's packet neighbor.
What does the OSPF state Exstart mean?
Currently negotiating the DD sequence numbers and master/slave logic used for DD packets.
What does the OSPF state Loading mean?
All DD packets exchanged, and currently pulling the complete LSDB entries with LSU packets.
What does the OSFP state Full?
Neighbors are adjacent (fully adjacent), and should have identical LSDB entries for the area in which the link resides. Routing table calculations begin.
What could cause OSPF not to form neighbor relationship? 8
-Area (type)
-Timers
-MTU
-Duplicate Router IDs
-Passive interface
-Authentication
-Filtering (acl deny)
What is the description of the hello packet?
Used to discover neighbors, bring a neighbor relationship to a
2-Way state, and monitor a neighbor’s continuous liveliness
What is the description of the Database Description (DD
or DBD)?
Used to exchange LSA headers during the initial topology
exchange, so that a router knows a list of that neighbor’s
LSAs including their versions
What is the description of the Link-State Request (LSR)?
A packet that identifies one or more LSAs about which the
sending router would like the neighbor to supply full details
about the LSAs
What is the description of the Link-State Update (LSU)?
A packet that contains fully detailed LSAs, sent in response
to an LSR message or in the event of a topological change
What is the description of the Link-State Acknowledgment
(LSAck)?
Where are OSPF packets used?
What is the sequence for OSPF to choose RID?
-Use highest IP number of nonshutdown local loopback interface
-Use highest IP number of nonshutdown nonlocalloopback interface
What is the command to show ospf border-routers?
OSPF Process 1 internal Routing Table
Codes: i – Intra-area route, I – Inter-area route
i 1.1.1.1 [64] via 10.3.13.1, Serial0/0.1, ABR, Area 3, SPF 30
I 7.7.7.7 [65] via 10.3.13.1, Serial0/0.1, ASBR, Area 3, SPF 30
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