OSPF and First-Hop Redundancy Quick Reference for CCNA 200-301 v2.0

Cisco's published 200-301 v2.0 blueprint includes single-area Open Shortest Path First version 2 (OSPFv2), Open Shortest Path First version 3 (OSPFv3), and operational interpretation of Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP). Cisco says v2.0 begins February 3, 2027.

This page is for fast routing-state decisions. Use the full Domain 3 guide when the underlying configuration still needs teaching.

1. Routing-protocol decision map

2. Troubleshoot OSPF in layers

When OSPF routes are missing, separate interface state, adjacency, and route installation.

1. Interface and Layer 3 state

Start with evidence such as:

show ip interface brief
show ip ospf interface brief
show ip ospf interface GigabitEthernet0/0/0

Confirm:

• The interface is operational.
• IPv4 addressing and subnet placement are compatible for OSPFv2 neighbors on the link.
• OSPF is enabled on the intended interface.
• The interface belongs to the intended area.
• The expected network type is in use.

2. Neighbor relationship

Then check:

show ip ospf neighbor

Useful compatibility checks include:

• Area
• Hello/dead timers
• Unique router IDs
• Network type
• IP connectivity on the shared link
• MTU when adjacency stalls during database exchange

The v2.0 adjacency objective explicitly excludes authentication from this subtopic, so do not invent an authentication problem when the evidence points to a basic adjacency mismatch.

3. Learned and installed routes

After adjacency works:

show ip route ospf
show ip protocols

A FULL neighbor proves adjacency completed. It does not prove every expected prefix is being advertised or installed.

If the neighbor is healthy but the route is absent, ask whether:

• The intended network participates in OSPF.
• The prefix is present in the OSPF database.
• A competing installed route is preferred.
• The expected address family is being examined.

3. Use neighbor states to narrow the fault

Do not memorize the list without the diagnostic meaning. The state tells you how far OSPF got.

4. Separate point-to-point and broadcast expectations

Point-to-point

A point-to-point OSPF network has two routing devices for OSPF purposes.

• No Designated Router (DR) election
• No Backup Designated Router (BDR) election
• The two peers should form the expected adjacency directly

Useful evidence:

show ip ospf interface
show ip ospf neighbor

Broadcast

Ethernet commonly uses the OSPF broadcast network type. A shared segment can contain several routers, so OSPF elects a DR and BDR.

Election clues:

• Interface priority is considered among eligible routers.
• Priority 0 makes a router ineligible to become DR or BDR.
• Router ID breaks a priority tie.
• The election is not continuously re-run simply because a router with a higher priority appears later.

A DROTHER router can be 2-WAY with another DROTHER and still be operating normally. Expect FULL adjacencies with the DR and BDR.

5. Treat the router ID as protocol identity

The OSPF router ID is a 32-bit identifier written in dotted-decimal form.

Explicit configuration makes the identity predictable:

router ospf 10
 router-id 1.1.1.1

Keep these distinctions clear:

• The process ID is locally significant. Neighboring routers do not need matching OSPF process IDs.
• Router IDs should be unique.
• A router ID identifies the OSPF router; it is not the same thing as the next-hop address used to forward user traffic.
• Changing the configured router ID may require the OSPF process to restart or reset before the operational ID changes.

Verify rather than assuming:

show ip ospf
show ip ospf neighbor

6. Apply the same troubleshooting structure to OSPFv3

The published v2.0 blueprint pairs OSPFv3 with IPv6.

Current IOS XE syntax can look like:

ipv6 unicast-routing
!
router ospfv3 10
 router-id 1.1.1.1
!
interface GigabitEthernet0/0/0
 ospfv3 10 ipv6 area 0

Useful evidence includes:

show ospfv3 interface brief
show ospfv3 neighbor
show ospfv3 database
show ipv6 route ospf

Use the same order:

1. IPv6/interface state
2. OSPFv3 enabled on the intended interface/area
3. Neighbor relationship
4. Database/prefix presence
5. IPv6 route installation

OSPFv3 commonly uses IPv6 link-local addresses for neighbor communication. Pay attention to the interface associated with the neighbor instead of reading only the address.

7. Read HSRP and VRRP as gateway availability

First-hop redundancy lets hosts keep one virtual default-gateway address while multiple routers coordinate forwarding responsibility.

For either protocol, identify:

• Virtual IP address
• Local router role
• Peer role
• Priority
• Preemption behavior where configured
• Interface/group state

If the wrong router owns the forwarding role, check priority, preemption, peer reachability, and interface state before changing the virtual IP.

FHRP does not change the host's default gateway during normal failover. The router performing the forwarding role changes while the virtual gateway remains the stable host-facing address.

8. IOS evidence map

9. Scenario comparisons

OSPF neighbors never appear

Start before the routing table. Verify interface state, addressing, OSPF enablement, area, timers, and Hello reachability.

Two Ethernet routers remain 2-WAY, but both are DROTHER

That can be normal on a broadcast segment. Check their relationships with the DR/BDR before calling it an adjacency failure.

Neighbor is FULL, but one expected prefix is missing

Move past adjacency. Check whether the prefix is being advertised and whether another route source is preferred.

OSPFv2 process IDs differ on adjacent routers

That alone is not a problem. The process ID is locally significant.

HSRP virtual gateway answers, but the design expects the other router to be Active

Inspect priority, preemption, peer/interface state, and the current HSRP role rather than changing host default gateways.

VRRP shows the local device as Backup

That is not a fault by itself. Verify which router is Master and whether that matches the intended priority/state.

10. Common exam traps

• Looking for OSPF routes before proving adjacency.
• Treating a FULL neighbor as proof every prefix should be installed.
• Assuming OSPF process IDs must match.
• Assuming every OSPF neighbor pair on Ethernet must be FULL.
• Treating 2-WAY as automatically broken on a broadcast segment.
• Expecting DR/BDR on a point-to-point OSPF link.
• Treating a router ID as a packet-forwarding next hop.
• Ignoring MTU when adjacency stalls during database exchange.
• Troubleshooting OSPFv3 without checking IPv6/interface state first.
• Treating HSRP Active/Standby terminology as interchangeable with VRRP Master/Backup output.
• Changing the virtual gateway address when the actual issue is FHRP role selection.
• Assuming higher configured priority immediately replaces the current DR or FHRP forwarder without considering election/preemption behavior.

11. Rapid review grid

12. Official references

• Cisco 200-301 CCNA v2.0 Exam Topics
• Cisco IOS XE OSPF configuration
• Cisco IOS XE OSPFv3 for IPv6
• Cisco HSRP documentation
• Cisco VRRP documentation