Click the exhibit. Router R1 is a route reflector with clients R2, R5 and R6. Prefixes advertised by router R5 have a local preference of 200. Router R3 advertises the prefix 192.168.1.0/27 to…

Question

Options

• ANextHop LocalPref MED Path-Id VPNLabel As-Path u* >i 192.168.1.0/27 200 None - 65541 10.10.10.5 65541
• BNextHop LocalPref MED Path-Id VPNLabel As-Path u* >i 192.168.1.0/27 None None - 65541 10.5.5.3 65541 i 192.168.1.0/27 200 None - 65541 10.10.10.5 65541 i 192.168.1.0/27 100 None - 65541 10.10.10.6 65541
• CNextHop LocalPref MED Path-Id VPNLabel As-Path u* >i 192.168.1.0/27 None None - 65541 10.5.5.3 i 192.168.1.0/27 200 None - 65541 10.10.10.5
• DNextHop LocalPref MED Path-Id VPNLabel As-Path u* >i 192.168.1.0/27 200 None - 65541 10.10.10.5 i 192.168.1.0/27 100 None - 65541 10.10.10.6

• A
  10% (3)
• B
  3% (1)
• C
  70% (21)
• D
  17% (5)

Explanation

Option C is correct because advertise-external on R6 causes R6 to advertise its best eBGP-learned route from R3 to the route reflector R1 while preserving the original external next-hop (10.5.5.3 = R3), with no local-pref - R1 then reflects this path to R5 where it wins as best path due to its external-origin preference. R5 simultaneously sees its own iBGP advertisement reflected back by R1 as a secondary entry, with local-pref 200 and next-hop 10.10.10.5 (R5's own iBGP address), producing exactly the two-entry table in option C.

Why the distractors fail:

• A is wrong because it shows only R5's reflected route (lp=200), ignoring the advertise-external path entirely.
• B is wrong because it includes a separate R6 iBGP path (lp=100, nhop 10.10.10.6) - a standard route reflector only reflects its single best path, so R5 wouldn't see R6's iBGP path as a distinct entry.
• D is wrong for the same reason: it shows R6's path with nhop 10.10.10.6 (standard iBGP next-hop) instead of the external next-hop 10.5.5.3 that advertise-external preserves, and it incorrectly selects lp=200 as best rather than the external-origin path.

Memory tip: The giveaway for advertise-external in any route table output is an iBGP-flagged (i) route whose next-hop is an external (eBGP-facing) IP address - seeing 10.5.5.3 (R3's peering address) as a next-hop inside R5's iBGP table is only possible because R6 forwarded its external path to the RR with the original next-hop intact.

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