The sessions established between two routers in different autonomous systems are considered as External BGP (eBGP)
The NLRI announcements of other ASes usually contains the next-hop of the external neighbor router. This can be an issue for the iBGP sessions within our AS.
The next-hop is not modified when NLRIs are announced to a iBGP peer
It's common for the eBGP sessions to be established using the address of the physical interfaces that connect the routers. (RFC Compatible)
TTL-Security is an additional protection that we can implement to prevent certain attacks against the control plane. With it, we can discard attempts to start a session with a TTL < 255 - [CONF VALUE].
When a prefix is announced between eBGP peers, the AS-PATH attribute is altered to include the announcer AS.