300-410 VPN Technologies Practice Question
Which protocol should be used to dynamically distribute encryption keys for a GET VPN deployment?
⚠ Common exam trap
Test-takers frequently confuse GDOI with IKE; while IKE is used for point-to-point VPNs, GDOI is specifically designed for group key distribution in GET VPN.
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
✓
GDOI
GET VPN uses the Group Domain of Interpretation (GDOI) protocol for group key management. The key server uses GDOI to distribute encryption keys, rekey messages, and security policies to all group members. This allows members to encrypt traffic to each other without establishing point-to-point tunnels, preserving the any-to-any nature of the underlying network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
GDOI
Why this is correct
GDOI (Group Domain of Interpretation) is the protocol used in GET VPN to distribute group keys and policies from the key server to group members. It enables the key server to push encryption keys, rekey messages, and ACL policies to all group members, facilitating secure any-to-any communication without point-to-point tunnels.
- ✗
IKEv2
Why it's wrong here
IKEv2 is used for point-to-point IPsec VPNs to negotiate SAs and keys between two peers. While it can distribute keys, it is not designed for group key management. GET VPN requires a group key distribution protocol like GDOI, which scales to many members and supports rekeying.
- ✗
ISAKMP
Why it's wrong here
ISAKMP is the framework for authentication and key exchange used in IKEv1. It is not a group key distribution protocol. GET VPN uses GDOI, which runs over ISAKMP but adds group-specific extensions. ISAKMP alone cannot distribute group keys to multiple members.
- ✗
IPsec
Why it's wrong here
IPsec is the suite of protocols that provides encryption and authentication for IP packets. It does not distribute keys; it relies on a key management protocol like IKE or GDOI. In GET VPN, IPsec is used for data encryption, but GDOI handles key distribution.
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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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