300-420 · Question #191
300-420 Question #191: Real Exam Question with Answer & Explanation
The correct answer is C: VPNv4 unicast. In an MPLS Layer 3 VPN service, ISP PE routers must use a specific BGP address family to exchange customer routing information, ensuring isolation and support for overlapping IP addresses.
Question
An ISP provides Layer 3 VPN service over MPLS to a customer with four branches and multiple CE routers at each branch. To exchange the routes that are learned from the CE routers, which BGP address family should the ISP activate among the PE routers?
Options
- Aaddress-family multicast
- BL2VPN EVPN
- CVPNv4 unicast
- DIPv4 unicast
Explanation
In an MPLS Layer 3 VPN service, ISP PE routers must use a specific BGP address family to exchange customer routing information, ensuring isolation and support for overlapping IP addresses.
Common mistakes.
- A. The
address-family multicastis used for exchanging multicast routing information, typically within Multicast VPNs (MVPNs), not for standard unicast Layer 3 VPN routes. - B.
L2VPN EVPNis an address family primarily used for Layer 2 VPN services, such as extending Ethernet segments over an MPLS network, and does not handle Layer 3 IP route exchange in the same context. - D. The
IPv4 unicastaddress family is used for exchanging standard global IPv4 Internet routes between BGP peers and does not incorporate Route Distinguishers for VPN isolation, making it unsuitable for customer VPN routes in an MPLS L3VPN environment.
Concept tested. BGP address families in MPLS L3VPN (VPNv4)
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