You are logged into a Junos device and issue the command show route protocol bgp. You see that the device has received the route 10 0.4/24 from two different
IBGP peers. Local preference, MED, origin, and AS-path values are equal.
Which criterion is used to determine which path will be preferred?
Click on the arrows to vote for the correct answer
A. B. C. D.B
When a Junos device receives two similar route advertisements from different BGP peers, it will select the route will the lowest MED value. BGP route selection proceeds in this manner:
-> Prefer the highest local-preference value
-> Prefer the shortest AS-path length
-> Prefer the lowest origin value
-> Prefer the lowest MED value
-> Prefer routes learned from an EBGP peer over an IBGP peer
-> Prefer best exit from AS
-> For EBGP-receive routes, prefer the current active route:
-> otherwise, prefer routes from the peer with the lowest RID
-> Prefer paths with the shortest cluster length
-> Prefer routes from the peer with the lowest peer ID
When a router receives the same route from multiple sources, it must decide which route to use based on a set of criteria. In the case of BGP, the route selection process follows the rules specified in the BGP decision process.
According to the BGP decision process, the router first examines the attributes that have the highest priority. If there is a difference in any of these attributes between the routes, the router selects the route with the best attribute. If the attributes are the same, the router proceeds to the next set of attributes until it finds a difference.
The order of preference for the BGP attributes is:
In this scenario, the route has been received from two different iBGP peers, and the local preference, MED, origin, and AS-path values are equal. Therefore, the router will move to the next attribute, which is the eBGP path over the iBGP path. However, since both routes are from iBGP peers, this attribute is not useful in selecting the best path.
The next attribute is the lowest IGP metric to the next-hop router. However, since the routes have the same next-hop, this attribute is also not useful in selecting the best path.
The final attribute is the lowest router ID (RID) of the BGP speaker. Each BGP speaker is assigned a unique RID, and the router with the lowest RID is preferred. Therefore, the route with the lowest RID of the iBGP peer will be preferred.
Therefore, the answer is option B, router ID (RID).