hardMultiple Choice
300-410 Practice Question: Configures BGP synchronization on an iBGP router
A network engineer configures BGP synchronization on an iBGP router. The IGP (OSPF) does not carry the BGP routes. Unexpectedly, the router does not advertise these iBGP routes to eBGP neighbors. What is the most likely explanation?
⚠ Common exam trap
300-410 often tests BGP synchronization as a legacy feature — candidates forget that synchronization requires the route in the IGP and incorrectly blame next-hop-self or AS-path issues, missing the explicit synchronization rule.
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 router has 'bgp synchronization' enabled, and the iBGP route is not in the OSPF routing table, so it is not considered valid for advertisement.
BGP synchronization requires that a route learned via iBGP must also be present in the IGP (OSPF) routing table before it can be advertised to eBGP neighbors. If OSPF does not carry the BGP routes, the iBGP route is not synchronized and is therefore not considered valid for advertisement to eBGP peers. This is the classic behaviour of the synchronization rule.
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 router has 'bgp synchronization' enabled, and the iBGP route is not in the OSPF routing table, so it is not considered valid for advertisement.
Why this is correct
BGP synchronisation requires that a route learned via iBGP also be present in the IGP routing table before it is valid. Since OSPF does not carry the prefix, the route stays unsynchronised and is not advertised to eBGP peers.
- ✗
The router has 'bgp bestpath as-path multipath-relax' configured, which suppresses eBGP advertisements for iBGP routes.
Why it's wrong here
The as-path multipath-relax command affects BGP best-path selection for multipath, not advertisement suppression; iBGP routes are withheld from eBGP neighbours because BGP synchronisation requires the route in the IGP. It is tempting as a BGP tuning knob, but the actual cause is the synchronisation rule waiting on OSPF.
- ✗
The iBGP session is not using 'next-hop-self', so the next hop is unreachable.
Why it's wrong here
Synchronisation only blocks advertisement of iBGP-learned routes until the IGP carries them; next-hop reachability is a separate validation. The stem's OSPF not carrying the BGP routes is the direct trigger. 'next-hop-self' matters when advertising to iBGP peers across an IGP boundary, not for this suppression behaviour.
- ✗
The router has 'bgp suppress-duplicates' enabled, which drops identical routes.
Why it's wrong here
'bgp suppress-duplicates' affects duplicate route installation in the RIB, not the synchronisation rule that withholds iBGP routes from eBGP peers when the IGP lacks them. It is genuinely useful for suppressing identical multipath copies, but the stem's OSPF gap is what blocks advertisement here.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
About these practice questions
One of 1,401 original 300-410 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.