Exam JN0-649 topic 1 question 16 discussion

correct answer B. A routing policy will be required to forward traffic to both next hops. C. The TTL value of 1 is set to limit the scope of the EBGP session

B and C are correct. D can't be right because of this: Each router must establish the peering session with the loopback address of the remote router. You can configure this session using the local-address statement, which alters the peer address header information in the BGP packets. https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/multihop-sessions.html#:~:text=Each%20router%20must%20establish%20the%20peering%20session%20with%20the%20loopback%20address%20of%20the%20remote%20router

A. nope! clearly there is only one next-hop B. Yes! A routing policy will be required to forward traffic to both next hops. C. Yes! multihop is needed to extent the scope! but ttl is set to limit the scope of an EBGP sessions loopback; https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/multihop-sessions.html D. nope! Without the multihop statement, EBGP will only work on interface addresses of directly connected peer.

bc correct

How can C be correct when peering eBGP using loopbacks? Shouldn't a TTL of 2 be required to bring up the peering? The packet arrives with a TTL of one. The TTL is decremented to 0 and the packet discarded. Setting the TTL to 2 allows the peering to form using the loopbacks.

BC A. we can see the forwarding table only has one next hop (cant be this) B. technically true (but not the only requirement) C. true enough D. Technically the routers are directly connected, just not the peers cause its loopback to loopback, so in some ways its a semantics/wording of the question that needs to be noted.

B. You can apply export policies to routes being exported from the routing table into the forwarding table for the following features: Per-packet load balancing Class of service (CoS)

B - because only one next hop in forwarding table C- becuse TTL=1 limiting bgp connection to be established only over loopbacks interface https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/multihop-sessions.html Use the multihop statement to alter the default use of the neighbor's physical address. In addition, you can also specify a time-to-live (TTL) value in the BGP packets to control how far they propagate. We use a TTL value of 1 to ensure that the session cannot be established across any other backdoor links in the network.