Exam JN0-681 topic 1 question 16 discussion

it's clear

"The multipath statement overrides the default BGP routing behavior and allows two or more next hops to be used for routing"

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/bgp-multipath.html#id-understanding-bgp-multipath

only A makes sense.

A is correct

It should be A. I did a lab for this with Juniper ADCX course. The lab was 2 spine devices and 3 leaf devices. didn't have to configure add-path or multi-hop, only multipath multiple-as lab@spine1# show protocols bgp { group underlay { type external; export Export-Directs; local-as 65101; multipath { multiple-as; } neighbor 172.16.1.1 { peer-as 65201; } } group overlay { type internal; local-address 192.168.100.1; family evpn { signaling; } cluster 1.1.1.1; local-as 65000; neighbor 192.168.100.11; }

Add-path parameter is for iBGP, for ebgp once we configure underlay with separate AS numbers and once the leaf connects to 2 or more spines then it means that leaf is connected to 2 or more different ASs and leaf role is to load balance the traffic to all the spines, In this case if we do not use Multiple-AS with multipath then we will not be able to see all the routes. Hence It would be multipath multiple-as

I think it is B. add-path is basically the same as multipath, the only difference is that with add-path you have the control over the number of paths which you want installed in the forwarding table.

definitely multipath multiple-as

A correct. Peerings are OK so multipath multiple-as missing

All the adjacencies have formed according with the question; without multihop we are not able to estabilish a BGP session and then this isn't the missing parameter. If we are unable to see all the routes in a EBGP environment, multipath multiple-as must be added. https://www.juniper.net/documentation/en_US/junos/topics/topic-map/bgp-multipath.html (step n 2 of the configuration paragraph)

I think it is A. I don't see why you would ever need mutlihop to be configured in a Leaf/Spine Fabric using EBGP. Each leaf directly connected to each Spine. No Spine to Spine and no Leaf to leaf peering.

D: In EVPN DC setup for eBGP - you need to apply 'multihop ttl 2' to propagation routing between leaves - https://www.juniper.net/documentation/en_US/junos/topics/topic-map/multihop-sessions.html#id-example-configuring-ebgp-multihop-sessions

it should be B,