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300-410 Practice Question: R1 and R2 are connected via an IPsec VPN tunnel
R1 and R2 are connected via an IPsec VPN tunnel. R1 has a static route to 10.10.10.0/24 pointing to the tunnel interface. R2 has a static route to 192.168.1.0/24 pointing to the tunnel interface. Both routers have BGP configured between loopback addresses over the tunnel. BGP peering is established, but R1 cannot ping 10.10.10.1 (R2's loopback) from its loopback. R1's show ip bgp shows the route as valid but not best. What is the root cause?
⚠ Common exam trap
Cisco often tests the concept of recursive routing failure in IPsec VPN scenarios, where candidates mistakenly focus on BGP configuration issues (like next-hop-self or network statements) instead of recognizing that the tunnel destination must be reachable independently of the tunnel itself.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The static route to 10.10.10.0/24 via tunnel causes recursive routing failure because the tunnel destination is not reachable.
R1's static route to 10.10.10.0/24 points to the tunnel interface, but the tunnel destination (the remote peer's public IP) is not reachable via a valid routing path. This creates a recursive routing failure: the router tries to resolve the tunnel interface's next-hop (the tunnel destination) but cannot find a route to it, causing the BGP route to be marked as valid but not best. Without a reachable tunnel destination, the IPsec VPN cannot forward traffic, so pings from R1's loopback to 10.10.10.1 fail.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The static route to 10.10.10.0/24 via tunnel causes recursive routing failure because the tunnel destination is not reachable.
Why this is correct
The static route references the tunnel interface, but the tunnel's destination IP must be reachable via another route. If not, the route is invalid, and BGP cannot use the next-hop.
- ✗
BGP next-hop-self is not configured on R2.
Why it's wrong here
Next-hop-self would change the next-hop to R2's tunnel IP, but the issue is reachability of the next-hop, not its value.
- ✗
The IPsec tunnel is not encrypting BGP traffic.
Why it's wrong here
BGP peering is established, so IPsec is working for BGP traffic.
- ✗
The BGP network statement for 10.10.10.0/24 is missing on R2.
Why it's wrong here
R2 is advertising the route, as R1 sees it in BGP table.
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.