350-501 Services Practice Question
Which THREE characteristics apply to the BGP-LS (BGP Link State) protocol?
⚠ Common exam trap
Cisco often tests the misconception that BGP-LS only supports IS-IS (Option A) or that TE parameters are carried in the NLRI (Option E), when in fact BGP-LS supports both OSPF and IS-IS, and TE attributes are carried as sub-TLVs within the BGP-LS path attribute, not directly in the NLRI.
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
✓
It uses a separate address family from VPNv4.
BGP-LS uses a separate address family (AFI 16388 / SAFI 71) from VPNv4 (AFI 1 / SAFI 128) to carry link-state information. This separation allows BGP-LS to operate independently from VPNv4 routes, enabling the collection and distribution of IGP topology data without interfering with MPLS VPN signaling.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It supports only IS-IS, not OSPF.
Why it's wrong here
Both OSPF and IS-IS are supported.
- ✓
It uses a separate address family from VPNv4.
Why this is correct
BGP-LS uses AFI 16388, SAFI 71.
- ✓
It distributes link-state information from IGPs like OSPF and IS-IS.
Why this is correct
BGP-LS collects topology from IGPs.
- ✓
It uses BGP as the transport protocol.
Why this is correct
BGP-LS is an address family within BGP.
- ✗
It carries traffic-engineering parameters in the NLRI.
Why it's wrong here
TE parameters are carried in the BGP-LS attribute, not NLRI.
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.