An ExpressRoute circuit denotes the logical connectivity between MS cloud services and on- premises infrastructure via a connectivity provider. Which of the following statement(s) is/are true about…

Question

Options

• AExpressRoute circuits don't map to a physical entity
• BAn ExpressRoute circuit can be uniquely recognized by a service key (s-key)
• CAn ExpressRoute circuit can have one or a maximum of two peerings enabled per ExpressRoute
• DThere exists 1:1 mapping between ExpressRoute circuits and routing domains
• EThere exists 1:1 mapping between ExpressRoute circuits and the S keys

• A
  87% (53)
• C
  10% (6)
• D
  3% (2)

Explanation

Options A, B, and E are correct because an ExpressRoute circuit is purely a logical abstraction - it represents connectivity but does not correspond to any single physical entity (A). Each circuit is issued exactly one unique service key (s-key) by Microsoft, making the relationship bidirectional and 1:1 (B and E): one circuit has one s-key, and one s-key identifies one circuit.

C is wrong because an ExpressRoute circuit can support up to three routing domains/peerings (Azure Private Peering, Azure Public Peering, and Microsoft Peering), not a maximum of two.

D is wrong for the same reason: a single circuit maps to multiple routing domains (1:many), not a 1:1 relationship - the 1:1 constraint applies to s-keys, not routing domains.

Memory tip: Think of the s-key like a passport number - one person (circuit) gets exactly one passport number (s-key), uniquely identifying them globally. The circuit is the "person" (logical, not physical), and they can have multiple visas (peering types/routing domains) stamped in that passport. The 1:1 rule is for s-keys only; everything else about an ExpressRoute circuit is flexible and can scale to multiple instances.

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