An engineer must design a DNS service available to multiple network zones as a shared service. The network zones are deployed as VRFs within the data center network and no firewall is available for co

BGP is a routing protocol used for exchanging routing information between different routing domains or VRFs, but it does not inherently provide Layer 2 connectivity for a shared service across VRFs.

OSPF is an interior gateway protocol (IGP) used for routing within an autonomous system; it does not provide Layer 2 extension or a mechanism for sharing services across distinct VRFs.

ISIS is an interior gateway protocol (IGP) similar to OSPF, used for routing within an autonomous system; it does not provide Layer 2 extension or a mechanism for sharing services across distinct VRFs.

VXLAN (Virtual Extensible LAN) is required to extend Layer 2 networks over a Layer 3 underlay, enabling the shared DNS service to exist in a common Layer 2 segment that can then be made accessible to multiple VRFs. This allows the DNS server to be shared as a common endpoint without direct routing or firewall traversal between the isolated VRFs.