EBGP (External BGP) and IBGP (Internal BGP) operate with different rules due to the nature of their relationships.
Step-by-Step Breakdown:
TTL Differences:
EBGP: By default, EBGP peers have a TTL of 1, meaning they must be directly connected, or the TTL needs to be manually increased for multihop EBGP.
IBGP: IBGP peers within the same AS have a TTL of 255, as they are expected to communicate over multiple hops within the AS.
Preference for EBGP Routes:
Routes learned via EBGP are typically preferred over IBGP routes. This is because EBGP routes are considered more reliable since they originate outside the AS, while IBGP routes are internal. Juniper Reference: BGP Configuration: The different handling of TTL and route preferences between EBGP and IBGP ensures proper route selection and security within Junos-based networks.

In Layer 2 switching, switches learn MAC addresses based on the source MAC address of incoming frames and forward frames based on the destination MAC address.
Step-by-Step Breakdown:
MAC Learning:
When a switch receives a frame, it records the source MAC address and the port on which it arrived. This allows the switch to know where to send traffic destined for that MAC address.
Forwarding Based on Destination:
The switch then looks at the destination MAC address and forwards the frame out of the port associated with that MAC address. If the MAC is unknown, the switch floods the frame to all ports.
Juniper Reference:
Layer 2 Switching: Juniper switches use source MAC addresses to build MAC tables and forward traffic based on the destination MAC address.