Which BGP attribute can be used to influence the path that outgoing traffic takes from your AS to other Autonomous Systems? (Choose two.)
Which BGP attribute can be used to influence the path that outgoing traffic takes from your AS to other Autonomous Systems? (Choose two.)
To influence the path that outgoing traffic takes from your AS to other Autonomous Systems, use the Weight and Local Preference BGP attributes. Weight is a locally significant attribute that influences the path selection on a specific router; higher weights are preferred. It is only relevant to the router on which it is configured and affects how traffic exits that particular router. Local Preference, on the other hand, is propagated throughout an entire AS and influences the route selection for all routers in the AS; routes with higher local preference values are preferred. AS_Path and MED are not used to influence outgoing traffic paths from your AS to other Autonomous Systems; AS_Path influences incoming traffic, while MED influences how other ASs send traffic to your AS.
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.
However not a typical case, as-path prepend used outbound is also possible. https://blog.ipspace.net/2009/03/as-path-prepending-technical-details.html
Provided answer is correct, its Weigth and Local preference. AS Path is used to influence incoming traffic not outgoing. You can use it to influence incoming traffic but is not recomended. @Titini "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 " - you dont understand what tha 'AS' is, you can have huge autonomous system network and olny one BGP router. So still you cant use Weigth?
Provided answer is correct, its Weigth and Local preference. AS Path is used to influence incoming traffic not outgoing. You can use it to influence outgoing* traffic but is not recomended.
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.
C, D is correct. AS-PATH with the prepend I can use polcy traffi inside AS
C and D easily
C, D is correct. https://networklessons.com/bgp/bgp-attributes-and-path-selection
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
Local preference is Never Shared Between eBGP Peers, Any BGP router that receives a LOCAL_PREF attribute from an eBGP peer must ignore it (except in the case of BGP confederations)
you are wrong my friend. We have policy outside our AS, with we can use LOCAL PREFERENCE for that
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
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.
And AS_pAth is obvious. I will go with B and D.
Correction: C and D is best.
B and D are correct answer
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.
I voted C, D, because weight (C) can be used for dual-home network scenarios. Weight is only locally relevant, however, if there is only one border router for eBGP peering it can be used to manipulate outbound traffic out of one AS towards other ASs. https://community.cisco.com/t5/other-network-architecture-subjects/bgp-inbound-and-outbound-traffic/td-p/337728 I do not doubt that B (AS-path prepend) is correct, too. I just can't choose between B and C. As-path prepend used outbound is also possible. Example: https://blog.ipspace.net/2009/03/as-path-prepending-technical-details.html
I am still not sure whether it's B or C. OCG for ENARSI says: "Weight can be set for specific routes with an inbound route map or for all routes learned from a specific neighbor. Weight is not advertised to peers and only influences outbound traffic from a router or an AS." Then there is a picture with a topology where weight is set on two routers of the same AS, and outgoing path is only manipulated by weight from that AS. Which part are you referring to in OCG?
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.
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!!
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
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
C & D are correct