iBGP: -


iBGP Rules:
Rule 1 – Must be in same AS
Rule 2 – TTL is 255 (doesn't have to be directly connected)
Rule 3 – If route learned from a iBGP neighbor, it cannot be advertised to another iBGP neighbor.
Rule 4 – If router has both eBGP and iBGP neighbors, use 'next hop self' toward other iBGP neighbors.

iBGP Well Known Mandatory Attributes (AON):
AS Path
Origin Code
Next Hop

iBGP Checks:
Before Adding to BGP Table
Check 1 – Is it a valid update?
Contain AS Path?
Contain Origin Code?
Contain Next Hop?

Before Adding to Route Table
Check 1 – Is the next hop reachable?
If yes, route placed into route table.
Does not get added to routing table.