Comprehensive and Detailed In-Depth Explanation:
Understanding the BGP and IS-IS Network Topology in the Question:
* IS-IS Areas:
* Area 49.0001 (Level-1 IS-IS): R1, R2, R4, R5.
* Area 49.0002 (Level-2 IS-IS): R3, R6.
* R2 acts as an ABR (Area Border Router) and redistributes routes between Level-1 and Level-2 using import-route isis level-2 into level-1.
* BGP Route Reflection & Peering:
* R2 and R5 are Route Reflectors (RRs).
* iBGP peering is established among all routers (R1, R2, R3, R4, R5, R6).
* R1 and R4 import 192.168.1.0/24 into BGP, meaning this prefix will be advertised to all iBGP peers.
* R3 and R6 import 192.168.2.0/24 into BGP, meaning this prefix will also be advertised to all iBGP peers.
Route Distribution Analysis:
Route to 192.168.1.0/24 (Imported by R1 & R4):
* R1 and R4 advertise 192.168.1.0/24 into iBGP.
* Since R2 and R5 are Route Reflectors (RRs), they will reflect these routes to all their iBGP clients (R1, R3, R4, R6).
* R2 learns two valid routes to 192.168.1.0/24 (from R1 and R4).
* R5, as another RR, learns both routes and advertises them as well.
* R2 ultimately has three valid paths (direct from R1 and R4, plus a reflected route from R5).# Statement C is correct: The BGP routing table of R2 contains three valid routes to 192.168.1.0/24.
* R5 also learns 192.168.1.0/24 from both R1 and R4.# Statement B is correct: The BGP routing table of R5 contains two valid routes to 192.168.1.0/24 (from R1 and R4).
Route to 192.168.2.0/24 (Imported by R3 & R6):
* R3 and R6 import 192.168.2.0/24 into BGP.
* R2 and R5 (Route Reflectors) learn this route and reflect it to their clients (R1, R3, R4, R6).
* R4 receives three valid paths (directly from R3 and R6 via BGP, and one additional reflected path via R5).# Statement D is correct: The BGP routing table of R4 contains three valid routes to
192.168.2.0/24.
Checking Statement A:
* R3 originally imports 192.168.2.0/24 and advertises it.
* Since it is a Route Reflector Client of R5 and R2, it should have multiple routes via iBGP, not just one.# Statement A is incorrect because R3 should have multiple valid routes, not just one.
Final Conclusion:
# B. The BGP routing table of R5 contains two valid routes to 192.168.1.0/24.# C. The BGP routing table of R2 contains three valid routes to 192.168.1.0/24.# D. The BGP routing table of R4 contains three valid routes to 192.168.2.0/24.# A. The BGP routing table of R3 does NOT contain only one valid route to 192.168.2.0/24 (it has multiple routes).
Thus, the correct answers are: B, C, D.