Comprehensive and Detailed In-Depth Explanation:

1. Understanding Route Targets (RT) and Route Distribution in MPLS VPN

MPLS Layer 3 VPNs (L3VPNs) use BGP to distribute VPN routes across multiple Provider Edge (PE) routers.

Each VPN instance (VRF) is configured with Route Targets (RTs) to control which VPN routes are imported/exported.

Route Distinguishers (RDs) are unique per VRF but do not affect route selection.

2. Analyzing VPN1 Configuration

VPN1 is exporting routes with the following Route Targets (vpn-target values):

100:1

200:1

300:1

Remote VPNs will import these routes only if their import RT list matches one of the exported RTs.

3. Matching Exported RTs with Import RTs in Remote VPNs

Remote VPN

Import RTs

Matches VPN1 Exported RTs (100:1, 200:1, 300:1)?

Accepts the Route?

VPN1

100:1

✅ Matches 100:1

✅ Yes

VPN2

200:1, 400:1

✅ Matches 200:1

✅ Yes

VPN3

100:1, 300:1

✅ Matches 100:1, 300:1

✅ Yes

VPN4

500:1

❌ No match

❌ No

✅ VPN1, VPN2, and VPN3 accept the route.

❌ VPN4 does not accept the route because 500:1 is not in the export list of VPN1.

Final Conclusion:

✅ Correct Answer: VPN1, VPN2, and VPN3 will accept the route.

❌ VPN4 does not accept the route because there is no matching RT.

Thus, the correct answer is:

✅ A. VPN1: Import RT=100:1

✅ B. VPN2: Import RT=200:1, 400:1

✅ C. VPN3: Import RT=100:1, 300:1

❌ D. VPN4: Import RT=500:1 (No match, does not accept the route).