Question 771 of 2,152

Route Redistribution →hardMultiple ChoiceObjective-mapped

Why BGP Advertised Routes Show Next Hop 0.0.0.0 and How to Fix

This 300-410 practice question tests your understanding of route redistribution. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

A network engineer runs the following command on Router R1:

R1# show ip bgp neighbors 10.2.2.2 advertised-routes

BGP table version is 10, local router ID is 1.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path *> 10.1.1.0/24 0.0.0.0 0 32768 i *> 10.2.2.0/24 0.0.0.0 0 32768 i

Total number of prefixes 2

Based on this output, what is the problem?

A
The routes are correctly advertised with next hop 0.0.0.0, which is normal for locally originated routes.
Correct. The next hop 0.0.0.0 is normal for locally originated routes, and the router will adjust it when advertising to eBGP peers.
B
The routes are not being advertised to eBGP peers because the next hop is 0.0.0.0, which is invalid for eBGP.
Why wrong: Incorrect. The next hop 0.0.0.0 is not an issue; BGP automatically sets the next hop to the router's interface IP for eBGP advertisements.
C
The routes are being advertised to iBGP peers only, as indicated by the next hop 0.0.0.0.
Why wrong: Incorrect. The output does not indicate that routes are only advertised to iBGP; it shows routes in the BGP table which can be advertised to both iBGP and eBGP.
D
The routes are redistributed from an IGP into BGP, and the next hop is correctly set to 0.0.0.0.
Why wrong: Incorrect. While the routes may be redistributed, the next hop 0.0.0.0 is still normal and does not indicate a problem.

Full breakdown with real-world context →

Quick Answer

The problem is that the routes are being advertised with a next hop of 0.0.0.0, which is invalid for eBGP and prevents them from being installed in the neighbor’s routing table. In BGP, a next hop of 0.0.0.0 indicates a locally originated route, typically injected via a network statement or redistribution, but for eBGP advertisements, the router must update the next hop to its own outbound interface IP address. This output from the `show ip bgp neighbors advertised-routes` command is a classic trap on the Cisco CCNP ENARSI 300-410 exam, testing your understanding of BGP next-hop processing and the rule that eBGP peers reject routes with a next hop of 0.0.0.0 unless the `next-hop-self` command is misapplied or missing. The fix often involves ensuring the correct interface IP is used or applying `neighbor x.x.x.x next-hop-self` under the BGP process. Memory tip: think of 0.0.0.0 as a “local only” sign—it means the route stays home and never leaves for an eBGP neighbor.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The routes are correctly advertised with next hop 0.0.0.0, which is normal for locally originated routes.

The output shows that R1 is advertising two routes to the BGP neighbor 10.2.2.2. Both routes have a next hop of 0.0.0.0, which is normal for locally originated routes (e.g., via network statement or redistribution). When advertising to an eBGP peer, the router automatically changes the next hop to its own interface IP address if the next hop is not reachable via the eBGP neighbor. However, the 'show ip bgp neighbors advertised-routes' command displays the routes as they are in the BGP table, not the actual advertisement sent. The next hop 0.0.0.0 indicates the route is local, and BGP will update it appropriately when sending to an eBGP peer. Therefore, there is no problem; the routes are being advertised correctly.

Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
The routes are correctly advertised with next hop 0.0.0.0, which is normal for locally originated routes.
Why this is correct
Correct. The next hop 0.0.0.0 is normal for locally originated routes, and the router will adjust it when advertising to eBGP peers.
Related concept
OSPF neighbours must agree on key parameters.
✗
The routes are not being advertised to eBGP peers because the next hop is 0.0.0.0, which is invalid for eBGP.
Why it's wrong here
Incorrect. The next hop 0.0.0.0 is not an issue; BGP automatically sets the next hop to the router's interface IP for eBGP advertisements.
✗
The routes are being advertised to iBGP peers only, as indicated by the next hop 0.0.0.0.
Why it's wrong here
Incorrect. The output does not indicate that routes are only advertised to iBGP; it shows routes in the BGP table which can be advertised to both iBGP and eBGP.
✗
The routes are redistributed from an IGP into BGP, and the next hop is correctly set to 0.0.0.0.
Why it's wrong here
Incorrect. While the routes may be redistributed, the next hop 0.0.0.0 is still normal and does not indicate a problem.

Common exam traps

Common exam trap: OSPF can fail even when IP connectivity looks correct

OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.

Trap categories for this question

Command / output trap
Incorrect. The output does not indicate that routes are only advertised to iBGP; it shows routes in the BGP table which can be advertised to both iBGP and eBGP.

Detailed technical explanation

How to think about this question

OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.

KKey Concepts to Remember

OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.

TExam Day Tips

Check area mismatch first when OSPF adjacency fails.
Review passive interfaces when a network is advertised but no neighbour forms.
Use show ip ospf neighbor and show ip route clues carefully.

Key takeaway

OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Real-world example

How this comes up in practice

A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

What to study next

Got this wrong? Here's your next step.

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

Route Redistribution — This question tests Route Redistribution — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The routes are correctly advertised with next hop 0.0.0.0, which is normal for locally originated routes. — The output shows that R1 is advertising two routes to the BGP neighbor 10.2.2.2. Both routes have a next hop of 0.0.0.0, which is normal for locally originated routes (e.g., via network statement or redistribution). When advertising to an eBGP peer, the router automatically changes the next hop to its own interface IP address if the next hop is not reachable via the eBGP neighbor. However, the 'show ip bgp neighbors advertised-routes' command displays the routes as they are in the BGP table, not the actual advertisement sent. The next hop 0.0.0.0 indicates the route is local, and BGP will update it appropriately when sending to an eBGP peer. Therefore, there is no problem; the routes are being advertised correctly.

What should I do if I get this 300-410 question wrong?

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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