Which three statements correctly describe the default BGP advertisement behavior in the Junos OS? (Choose three.)
A.
Routes learned through EBGP are advertised to IBGP peers.
B.
Routes learned through EBGP are advertised to other EBGP peers.
C.
Routes learned through IBGP are advertised to other IBGP peers.
D.
Routes learned through IBGP will be advertised to EBGP peers.
E.
Routes learned through an IGP are automatically advertised to EBGP peers.
Explanation:
By default, only active BGP routes are advertised. The graphic illustrates the default BGP advertisement rules. The
rules are as follows:1. IBGP peers advertise routes received from EBGP peers to other IBGP peers.
2. EBGP peers advertise routes learned from IBGP or EBGP peers to other EBGP peers.
3. IBGP peers do not advertise routes received from IBGP peers to other IBGP peers.The purpose of the advertisement rules is to prevent routing loops on a BGP network.
Each BGP speaker advertises to its peers the routes to prefixes that it can reach. These routes include:
Routes to prefixes originating within the speaker’s AS
Routes redistributed from another protocol, including static routesEach BGP speaker advertises to its peers the routes to prefixes that it can reach. These routes include:
Routes to prefixes originating within the speaker’s AS
Routes redistributed from another protocol, including static routesBy default, BGP does not advertise any route unless the router’s IP routing table also contains the route.
When you establish a BGP relationship with a peer, your BGP session is either an internal BGP (IBGP) or external BGP (EBGP) session. Determining which kind of session you are establishing is simple. If the two peers are in the same AS, the BGP session is an IBGP session. If the two peers are in different ASs, the BGP session is an EBGP session.
The type of relationship affects the path selection algorithm, the way routes are propagated, and the guidelines and constraints that affect session establishment.
IBGP speakers send routes to their IBGP peers that they received from EBGP peers and routes that they originated themselves. IBGP speakers never send routes to IBGP peers that they learned from other IBGP peers. For all IBGP speakers in an AS to have consistent routing information, there must be a full mesh of IBGP sessions between all BGP speakers. Without this full mesh, some BGP speakers might not receive all the required routing information.