300-410 · Question #69
Refer to the exhibit. In which circumstance does the BGP neighbor remain in the idle condition? R200#show ip bgp summary BGP router identifier 10.1.1.1, local AS number 65000 BGP table version is…
The correct answer is D. If prefixes exceed the maximum limit. The BGP neighbor remains in the Idle state with a 'PfxCt' (Prefix Count) indication when the number of received prefixes from that neighbor exceeds the configured maximum limit.
Question
Options
- AIf prefixes are not received from the BGP peer
- BIf prefixes reach the maximum limit
- CIf a prefix list is applied on the inbound direction
- DIf prefixes exceed the maximum limit
How the community answered
(33 responses)- A6% (2)
- B3% (1)
- D91% (30)
Why each option
The BGP neighbor remains in the Idle state with a 'PfxCt' (Prefix Count) indication when the number of received prefixes from that neighbor exceeds the configured maximum limit.
If prefixes are not received, the neighbor might be in a 'Connect' or 'Active' state if it's attempting to establish, or 'Established' with zero prefixes if the session is up but no routes are exchanged.
If prefixes merely 'reach' the maximum limit, a warning might be issued, but the session typically enters Idle only if the limit is 'exceeded' and a reset action is configured.
Applying an inbound prefix list filters which prefixes are accepted into the routing table, but it does not cause the BGP session itself to enter the `Idle (PfxCt)` state; the session would likely remain 'Established' with fewer prefixes received.
The `Idle (PfxCt)` state in BGP summary output specifically indicates that the BGP session was torn down because the router received more prefixes than the configured `maximum-prefix` limit from that particular neighbor. Exceeding this limit prevents the BGP session from establishing or keeps it in the Idle state to protect the router's resources.
Concept tested: BGP neighbor states, maximum-prefix limit
Source: https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/211516-bgp-states-explanation.html
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