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Cisco CCNA 3.4
TechKnowSurge Catalog Interactives Which OSPF Neighbor State?
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Which OSPF Neighbor State?

Hellos with no reply, DBD headers flying, two DROthers side by side: which neighbor state is it?

⚑ Complete this interactive to capture a CTF flag worth 5 points.

About this interactive

An OSPF neighborship moves through these states (Attempt, used only on some NBMA networks, is left out, as in the lesson): 1. **Down**: hellos sent, none received. 2. **Init**: a hello has arrived, but it does not list this router's ID. 3. **2-Way**: each sees its own ID in the other's hello. The DR and BDR are elected here. 4. **ExStart**: the pair agree who is primary (the higher router ID) and the first sequence number. 5. **Exchange**: database description packets carry LSA headers. 6. **Loading**: link-state requests and updates fetch the full LSAs that are missing. 7. **Full**: the databases are in sync. On a converged multi-access segment, every router is Full with the DR and BDR, and two DROthers stay 2-Way.

What you'll learn

Aligned to

Cisco CCNA
3.4 Configure and verify single area OSPFv2

Key terms

OSPF Neighbor Adjacency
A relationship formed between two OSPF routers on the same network segment after successfully exchanging hello packets with matching parameters.
Backup Designated Router
BDR
An OSPF router elected on a multi-access network segment as the backup to the Designated Router, ready to take over DR functions if the DR fails. The BDR maintains adjacencies with all other routers on the segment to minimize reconvergence time.
Link State Advertisement
LSA
A packet generated by OSPF routers that describes the local router's links and their states, flooded throughout the OSPF area to build each router's link-state database. Different LSA types carry different information such as router links, network links, summary routes, and external routes.
Router ID
A 32-bit value formatted like an IP address that uniquely identifies an OSPF router and is used as a tiebreaker in DR/BDR elections when interface priorities are equal.

Topics

Ospf Neighbor States Adjacency Dr Bdr Interactive Categorize

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