Exam 350-401 topic 1 question 139 discussion

Weight only applies to the Router it is applied to, Local preference will apply to the whole AS group.

The given answer is correct

Default BGP Weight is 0. The higher the BGP Weight, the better. BGP Weight influences only the routing decisions of the local router where it is configured. BGP Weight determines which route to use to a given destination if multiple routes exist. Default local preference value is 100. BGP Local Preference influences exit points from the AS on all routers within the same AS because it is advertised to all routers.

A is correct the eggress interface on the SW4 must be modified, so local-preference must be be higher than the default value (100).

The given answer is correct

Local preference defaults to 100, and highest value wins so setting to 200 is the solution.

generally speaking it is EXIT point FROM AS: cisco(config-router)#bgp default ? inter-as-hybrid Configure Inter-AS Hybrid peer defaults ipv4-unicast Activate ipv4-unicast for a peer by default ipv6-nexthop Default IPv6 nexthop format local-preference local preference (higher=more preferred) route-target Control behavior based on Route-Target attributes cisco(config-router)#bgp default lo cisco(config-router)#bgp default local-preference ? <0-4294967295> Configure default local preference value cisco(config-router)#bgp default local-preference 200 cisco(config-router)#

Weight is Cisco proprietary and it is locally significant to the router and does not apply to the entire AS. Use Local Pref insteadl - A

This appears to be a tricky one. Both R3 and R4 have their local preference values defaulted to 200. They're both weighing their external neighbors at 200. That means this comes down to which AS 200 edge router BGP external peering and configs are applied first to determine through which edge router AS 200 egress to AS 100.

A correct weight i think when you have a edge router bgp with 2 link toward a diferent ISP router edge lpease someonde confirm me if it correct

Provided answer is correct

A https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html

I go for answer C BGP assigns the first valid path as the current best path. BGP then compares the best path with the next path in the list, until BGP reaches the end of the list of valid paths. This list provides the rules that are used to determine the best path: 1. Prefer the path with the highest WEIGHT. Note: WEIGHT is a Cisco-specific parameter. It is local to the router on which it is configured. 2. Prefer the path with the highest LOCAL_PREF. Note: A path without LOCAL_PREF is considered to have had the value set with the bgp default local-preferencecommand, or to have a value of 100 by default. https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13753-25.html

It seems Weight option (C) would be applicable if both exit peering links were on the same router, because Weight has local significance, also it requires peering routers to be Cisco, though weight attribute is supported in some other BGP implementation like VMware NSX-V.