Refer to the exhibit. A router is receiving BGP routing updates from multiple neighbors for routes in AS 690.
What is the reason that the router still sends traffic that is destined to AS 690 to a neighbor other than 10.222.1.1?
Refer to the exhibit. A router is receiving BGP routing updates from multiple neighbors for routes in AS 690.
What is the reason that the router still sends traffic that is destined to AS 690 to a neighbor other than 10.222.1.1?
The router is configured to assign a weight of 200 to routes learned from neighbor 10.222.1.1. BGP selects the path with the highest weight value when choosing between routes to the same destination. If the router sends traffic to AS 690 to a different neighbor, it indicates that there exists another path with a higher weight value than 200. Hence, the weight value in another neighbor statement being higher than 200 is the reason the router prefers a different neighbor for traffic destined to AS 690.
We=weight love=local preference oranges= originated locally >remotely as= as path oranges= origin code (IGP, EGP, incomplete?) mean= MED (metric) pure= eBGP > iBGP learned refreshment= highest RID.
Perfect example :)
Should be a, as weight values aren't shared between routers, but local preference is, correct?
Local Pref is shared in the same AS
Sharing is irrelevant. The question is about what THIS router does. We don't know (or care) if there even are other routers in this AS. On THIS router, we have assigned a weight to one neighbor, and (according to the correct answer) we have assigned a higher weight to a different neighbor.
But the question is about this router sending packets to another neighbor. Changing the weight on another router will have no impact on this router
What is the reason that the router (this router) still sends traffic that is destined to AS 690 to a neighbor other than 10.222.1.1? Local preference could be one reason. However this router set the weightto 200 for this neighbor. If this router set the weight to any matching prefixes, to higher than 200, for other neighbors, then the answer is D.
ip as-path access-list 200 permit ^690$ - prefixes originated in our neighbor AS 690 but neighbor 10.222.1.1 remote-as 1 This route-map will no be in use.
it is a wrong question as you stated above AS 1 and then AS 690 do not make any sense here
correct answer is not in options - router is sending traffic elsewhere, because it can never receive update matching as-path statement ^690$ from neighbor in AS 1. So it must receive update from other neighbors and that's why it sends it the other way. But when following "excluding wrong options" approach, D remains the last.
weight comes before local-pref in BGP routing decisional process
We all know Weight is local to each router, right? So if one of the neighbors has already been set to a weight of 200 (which one has in this config), then the only reason a third neighbor would be used is if weight of a third neighbor was higher. Because weight is more preferred than Local Pref, it won't matter what you set Local Pref to on any neighbor, the chosen one will always be the weight=200 UNLESS someone else has a higher weight. And don't forget, we're only looking at this one router, not a set of routers in an AS.
Not only is the situation described disgustingly, but also regexp will not match prefixes from AS1. We do not see the settings of "another neighbors". The question is obviously on the knowledge of path selection, but it is not clear where to apply this knowledge here ...
D is correct
I tested in GNS3 and router is choosing weight first between 2 eBGP neighbors for the same route.
Attributes are processed in the order : 1. Prefer the highest weight 2. Prefer the highest local preference D is ok
D is correct because we are only dealing with one router here, with its different bgp route statements.
Just D seems to be correct, because LOCAL-PREFERENCE is used for choosing best path between different routers.
Why does the neighbor have AS1, and we are waiting for updates from AS690?
The correct answer is: D
show ip bgp regexp ^100$ match the direct peering learned routes from as 100 ^$ - match locally originated routes only D makes sense
The AS of the router is 100, the neighbor 10.22.22.1 is AS 1, then the route announce to this must be eBGP route, and it must have a 1 prepend in it. The patten ^690$ shall match any path list that start with 690 and end with 690, so it should not set any weight nor local preference on that.. while local preference does not have effect, the weight should make it prefer to other, but it should not be advertised by other but rather have another setting to set the WEIGHT higher..
D is correct