Exam 300-410 topic 1 question 292 discussion

The BGP attributes that can be used to influence the path that outgoing traffic takes from your AS to other Autonomous Systems are AS_Path and Local Preference. The Weight attribute is useful for influencing the path of traffic within a single router, it cannot be used to influence the path of outgoing traffic from your AS to other Autonomous Systems.

C and D are correct. ASpath is only for manipulating incoming traffic to your AS, not outgoing.

Weight is a Cisco specific attribute so if your BGP peer uses a different vendor it might give you the finger. But as it's a Cisco exam I guess it's C & D.

The given answer is correct. C and D. AS_Path is used to influence incoming traffic, not outgoing.

C & D are correct

The answer provided is correct, the question is asking us to use attributes on our own routers to prefer a specific exit point, for doing so you can use weight in case you have just one router and you have to ISPs or in case you have more routers in your AS you use your local preference so that every router in your organization will use that exit point too

Inbound Route Policy is applied for Outbound PATH SELECTION: Weight Local Pref Outbound Route Policy is applied for Inbound PATH SELECTION: AS PATH (prepend) MED

Answers : C & D Both local pref and weight will be influencing routing when the route is LEAVING the local router. These will use “in” in the route map statement as they will modify the local pref or weight attribute after the BGP message is received. Once the modification is done, the new local pref or weight value will be applied when the traffic LEAVES the router. Wording of the question is confusing but logically only these are correct options. Tested in gns3 as well. AS path will be used as “out” in the route map statement and the AS path prepend will take place in the neighbor router hence the AS path prepend value will be visible when the traffic comes in. Hope its somewhat clear now!!

weight doesn't get advertised to other routers in your AS. Local preference does. So if you have 2 or more exit routers you set local preference so internal AS routers choose the appropriate exit router and final AS. With only one exit router you set Weight to choose the final AS.

Think B,C and D are all valid. Local preference is shared between router in the same OS whereas Weight and AS path manipulation need to be done per router via route maps/neighbor settings.

CD Practically B,C and D will do the job, however, using the BGP path selection order, I would go for C and D Priority Attribute 1 Weight 2 Local Preference 3 Originate 4 AS path length 5 Origin code

C, D is correct. https://networklessons.com/bgp/bgp-attributes-and-path-selection

C and D easily

C, D is correct. AS-PATH with the prepend I can use polcy traffi inside AS

per long time reserch, correct anwer is B D Weight is only right when in some special situation. You can read offical book P519-521, Then you can find the answer.

https://community.cisco.com/t5/routing/bgp-weight-local-preference-attributes-question/td-p/738421 https://community.cisco.com/t5/networking-knowledge-base/understanding-bgp-best-path-selection-manipulation/ta-p/3150576

C and D are correct. Weight is locally significant, but if you have one router that is dual-homed, you are still influencing egress traffic. Local pref is used for influencing egress traffic from your entire autonomous system, I.e you have two separate routers running iBGP with an uplink to a different ISP each.