hardMultiple ChoiceObjective-mapped
300-410 Practice Question: R1 and R2 have an IPsec VPN tunnel between their…
R1 and R2 have an IPsec VPN tunnel between their physical interfaces. They are running BGP over the tunnel interface. R1's show ip bgp summary shows the BGP session with R2 as established, but R1's show ip bgp shows no routes from R2. R2's show ip bgp shows routes from R1. What is the root cause?
⚠ Common exam trap
Cisco often tests the distinction between a BGP session being established (TCP state) and routes being exchanged (NLRI processing), so candidates may incorrectly assume that an established session guarantees route exchange, overlooking inbound route-map filtering.
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
✓
R1 has a route-map applied to the BGP neighbor inbound that denies all routes.
R1's BGP session is established (TCP port 179 is up), but no routes are received from R2. This indicates that an inbound route-map on R1 is filtering all incoming BGP updates. The route-map is applied to the neighbor inbound direction, which matches the symptom: R1 sees the session as established but has zero routes from R2, while R2 sees routes from R1 (since outbound filtering on R2 is not the issue).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R1 has a route-map applied to the BGP neighbor inbound that denies all routes.
Why this is correct
An inbound route-map can filter all incoming BGP updates, preventing routes from being installed in the BGP table.
- ✗
BGP next-hop-self is missing on R2.
Why it's wrong here
Missing next-hop-self would cause R1 to not have a route to the next-hop, but the routes would still appear in BGP table as not best.
- ✗
The IPsec tunnel is not encrypting BGP traffic.
Why it's wrong here
BGP session is established, so encryption is working.
- ✗
R2 is not advertising any networks.
Why it's wrong here
R2 sees routes from R1, so it is advertising.
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
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