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4A0-102 · Question #100

Click the exhibit.

The correct answer is C. C. Flag Network NextHop As-Path Path-Id LocalPref MED VPNLabel u*>i 192.168.1.0/27 None None - 10.3.5.3 65541 i 192.168.10.5 200 None - 65541 i 192.168.10.6 - None - 65541. Option C is correct because it accurately reflects the BGP VPN routing table where the route via 192.168.10.6 displays a dash (-) for LocalPref, indicating the Local Preference attribute is absent for that path - not set to zero or any numeric value - which is the correct Junos…

BGP Attributes and Path Selection

Question

Click the exhibit.

Options

  • AA. Flag Network NextHop As-Path Path-Id LocalPref MED VPNLabel u*>i 192.168.1.0/27 200 None - 10.3.5.3 65541
  • BB. Flag Network NextHop As-Path Path-Id LocalPref MED VPNLabel u*>i 192.168.1.0/27 None None - 10.3.5.3 65541 i 192.168.10.5 200 None - 65541 i 192.168.10.6 100 None - 65541
  • CC. Flag Network NextHop As-Path Path-Id LocalPref MED VPNLabel u*>i 192.168.1.0/27 None None - 10.3.5.3 65541 i 192.168.10.5 200 None - 65541 i 192.168.10.6 - None - 65541
  • DD. Flag Network NextHop As-Path Path-Id LocalPref MED VPNLabel u*>i 192.168.10.5/27 200 None - 65541 i 192.168.1.0/27 100 None - 10.10.0.6 65541

How the community answered

(56 responses)
  • A
    4% (2)
  • B
    2% (1)
  • C
    86% (48)
  • D
    9% (5)

Explanation

Option C is correct because it accurately reflects the BGP VPN routing table where the route via 192.168.10.6 displays a dash (-) for LocalPref, indicating the Local Preference attribute is absent for that path - not set to zero or any numeric value - which is the correct Junos behavior when a route lacks the attribute entirely (e.g., received from an eBGP peer without LocalPref propagation).

Option A is wrong because it collapses the table to a single entry with Path-Id 200, omitting the two additional i-flagged paths that should be present for this prefix. Option B is wrong because it assigns a LocalPref of 100 to the 192.168.10.6 path - a value that was never advertised; the attribute is simply missing, so the field should be a dash. Option D is wrong on two counts: the best path incorrectly shows 192.168.10.5/27 as the network (wrong prefix) and uses an invalid NextHop of 10.10.0.6.

Memory tip: In Junos routing table output, a dash (-) never means zero - it means the attribute is not present. If you see a numeric LocalPref (like 100 or 200), it was explicitly set; if you see -, the attribute simply wasn't advertised for that path.

Topics

#Best Path Selection#Local Preference#BGP Attributes#iBGP Routes

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