Quick Answer
The answer is the MCAST-VPN address family (AFI 25, SAFI 5). This is correct because in a draft-rosen MVPN with BGP signaling, the MCAST-VPN address family is specifically designed to carry multicast VPN routing information between PE routers, including Intra-AS I-PMSI A-D and S-PMSI A-D routes. Without this address family, BGP cannot exchange the multicast state and tunnel information needed to build the multicast distribution tree across the MPLS/VPN backbone. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of how MVPN signaling differs from unicast VPNv4 or VPNv6 address families—a common trap is confusing MCAST-VPN with the IPv4 multicast address family. Remember that for Layer 3 VPN multicast, you enable the MCAST-VPN address family under the BGP VRF configuration, not the global multicast BGP. A useful memory tip: think "MCAST-VPN for MVPN signaling" to avoid mixing it up with standard multicast routing.
This 350-501 practice question tests your understanding of services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 multicast solution for a Layer 3 VPN. They want to use MVPN with BGP signaling (draft-rosen). The PE routers are configured with VRF and multicast routing enabled. Which BGP address family must be enabled between PE routers to carry multicast routing information?
MCAST-VPN address family
The MCAST-VPN address family is used for MVPN signaling.
MVPN does not use BGP; it uses PIM.
Why wrong: draft-rosen uses BGP for auto-discovery and signaling.
VPNv4 address family
Why wrong: VPNv4 carries unicast routes only.
IPv4 multicast address family
Why wrong: Global multicast BGP is not for VPN context.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
MCAST-VPN address family
In a draft-rosen MVPN (Multicast VPN) implementation, BGP is used to signal multicast routing information between PE routers. The MCAST-VPN address family (AFI 25, SAFI 5) is specifically defined to carry multicast VPN routes, including Intra-AS I-PMSI A-D routes and S-PMSI A-D routes, enabling the exchange of multicast state and tunnel information across the MPLS/VPN backbone.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
MCAST-VPN address family
Why this is correct
The MCAST-VPN address family is used for MVPN signaling.
Related concept
Read the scenario before looking for a memorised answer.
MVPN does not use BGP; it uses PIM.
Why it's wrong here
draft-rosen uses BGP for auto-discovery and signaling.
VPNv4 address family
Why it's wrong here
VPNv4 carries unicast routes only.
IPv4 multicast address family
Common exam traps
Cisco often tests the distinction between the MCAST-VPN address family (used for MVPN signaling) and the VPNv4 address family (used for unicast VPN routes), leading candidates to mistakenly select VPNv4 when multicast is involved.
Detailed technical explanation
Under the hood, the MCAST-VPN address family uses BGP to advertise Type 1 (Intra-AS I-PMSI A-D) and Type 3 (S-PMSI A-D) routes, which carry the PMSI tunnel attribute (e.g., mLDP or P2MP RSVP-TE) and multicast source/group information. In a real-world scenario, this allows a service provider to interconnect multiple customer sites with multicast traffic while keeping each VRF isolated, using BGP as the scalable control plane instead of relying solely on PIM across the core.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 350-501 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Services — study guide chapter
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FAQ
Services — This question tests Services — Read the scenario before looking for a memorised answer..
The correct answer is: MCAST-VPN address family — In a draft-rosen MVPN (Multicast VPN) implementation, BGP is used to signal multicast routing information between PE routers. The MCAST-VPN address family (AFI 25, SAFI 5) is specifically defined to carry multicast VPN routes, including Intra-AS I-PMSI A-D routes and S-PMSI A-D routes, enabling the exchange of multicast state and tunnel information across the MPLS/VPN backbone.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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