nerdexam
Cisco

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.

Layer 3 Technologies

Question

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 26, main routing table version 26 1 network entries uses 132 bytes of memory 1 path entries uses 92 bytes of memory 2 BGP path/bestpath attribute entries using 296 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory Bifidist cache mines: current 1 (at peak 2) using 28 bytes of memory BGP using 248 total bytes of memory BGP activity 24/23 prefixes, 24/23 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.0.2.2 4 65100 20335 20329 0 0 0 00:02:04 Idle (PfxCt) R200#

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)
  • A
    6% (2)
  • B
    3% (1)
  • D
    91% (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.

AIf prefixes are not received from the BGP peer

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.

BIf prefixes reach the maximum limit

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.

CIf a prefix list is applied on the inbound direction

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.

DIf prefixes exceed the maximum limitCorrect

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

Topics

#BGP#BGP States#BGP Troubleshooting#Maximum Prefix

Community Discussion

No community discussion yet for this question.

Full 300-410 Practice