What is the incorrect characteristic of IBGP peers?

The distinguishing characteristic of Internal Border Gateway Protocol (IBGP) peers is that while they operate within the same Autonomous System (AS), they do not necessarily require direct physical connectivity. Instead, IBGP can function effectively through logical pathways created by other routers. This ability allows IBGP peers to communicate even if there are intermediary routers between them. The necessity of physical connectivity typically pertains to protocols that require direct link configurations, which does not apply to IBGP, where the connections can traverse multiple hops as long as there is a valid path.

The operation of IBGP within the same AS is fundamental, as it is designed to distribute external routing information (from Border Gateway Protocol, or BGP) among routers within a single AS. This centralizes the management of routing policies and ensures consistency across the network.

Regarding the requirement for SMTP connections, this is unrelated to IBGP, as SMTP pertains to mail transfer protocols, not routing protocols. Similarly, IBGP peers can only exchange routing information with other IBGP peers, highlighting the closed nature of IBGP communication, which further cements the understanding that the correct information characterizes their functionality, emphasizing peer relationships and connectivity conventions within an AS.