Which statement regarding internal BGP sessions is true?

When discussing internal BGP (iBGP) sessions, it's important to understand the characteristics that define their operation. The statement regarding the Time to Live (TTL) of BGP control packets being set to 255 is true. In the context of BGP, the default configuration for the TTL of its control plane packets is indeed set to 255. This design choice allows for the BGP session to be established between routers that may not be directly connected; it essentially limits the scope of BGP control packet transmission to a single hop unless explicitly configured otherwise.

When it comes to iBGP, routers typically only advertise routes to their iBGP peers that they have learned from other sources, but they must also adhere to the rule that iBGP peers must be fully meshed or utilize route reflectors to propagate routing information effectively. Therefore, the statement that routers advertise all BGP-learned routes to all internal BGP neighbors does not hold true in the traditional sense without additional configurations.

Regarding the use of physical interface IP addresses, while it’s common to use such addresses for iBGP peering, it is not a strict requirement; routers can be configured to use loopback addresses as well, which are often preferred for stability and