The correct answer is that BGP relies on an IGP for next-hop reachability within the AS. This is a fundamental characteristic of BGP in a service provider core because BGP, as a path-vector protocol, does not compute routes to the next-hop IP address of an IBGP or EBGP neighbor; instead, it depends on an underlying IGP like OSPF or IS-IS to provide that recursive routing information. In the Cisco SPCOR 350-501 exam, this concept tests your understanding of how BGP and IGP integrate in large-scale core networks, often appearing in questions about route propagation or IBGP design. A common trap is confusing this with BGP’s own loop prevention—remember that AS_PATH prevents loops in EBGP, not IBGP, while next-hop reachability always requires an IGP. Memory tip: “BGP knows the path, but IGP knows the next hop.”
350-501 Architecture Practice Question
This 350-501 practice question tests your understanding of architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 service provider is designing a BGP-based network. Which TWO are characteristics of BGP within a service provider core?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
IBGP sessions require a full mesh or route reflectors to avoid routing loops
In a service provider core, BGP typically uses IBGP full mesh or route reflectors, and integrates with IGP for next-hop reachability. BGP loop prevention via AS path is relevant for eBGP, not iBGP. MED is used for influencing inbound traffic, but it is an optional attribute. Route reflectors are common.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
IBGP sessions require a full mesh or route reflectors to avoid routing loops
Why this is correct
iBGP does not advertise routes learned from another iBGP peer to prevent loops; thus full mesh or RR is needed.
Related concept
Static NAT maps one inside address to one outside address.
✗
BGP MED attribute is mandatory for all routes
Why it's wrong here
MED is optional.
✗
BGP uses the AS path for loop prevention in iBGP
Why it's wrong here
AS path is used in eBGP; iBGP uses the originator_id and cluster_list for loop prevention.
✗
BGP route reflectors always modify the AS path
Why it's wrong here
Route reflectors do not modify the AS path.
✓
BGP relies on an IGP for next-hop reachability within the AS
Why this is correct
BGP next-hop must be reachable via IGP; otherwise, routes are not installed.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
Architecture — This question tests Architecture — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: IBGP sessions require a full mesh or route reflectors to avoid routing loops — In a service provider core, BGP typically uses IBGP full mesh or route reflectors, and integrates with IGP for next-hop reachability. BGP loop prevention via AS path is relevant for eBGP, not iBGP. MED is used for influencing inbound traffic, but it is an optional attribute. Route reflectors are common.
What should I do if I get this 350-501 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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