352-001 · Question #52
You are designing a Group Encrypted Transport virtual private network solution for an existing branch network. The existing network has the following characteristics: - 50 remote sites (with an…
The correct answer is C. No additional protocol is necessary. GETVPN preserves original IP headers, so existing routing protocols function without modification and no additional overlay routing protocol is required.
Question
You are designing a Group Encrypted Transport virtual private network solution for an existing branch network. The existing network has the following characteristics:
- 50 remote sites (with an additional 30 remote sites expected over the next 3 years)
- Connectivity between all sites is via Multiprotocol Label Switching Layer 3 virtual private network service
from a single provider
- Open Shortest Path First is the routing protocol used between provider edge and customer edge routers
- The customer edge routers will become group members performing the encryption between sites
Which additional routing protocol would you use for the overlay routing between the group members?
Options
- AOpen Shortest Path First (with a different process ID)
- BEnhanced Interior Gateway Routing Protocol
- CNo additional protocol is necessary.
- DExternal Border Gateway Protocol
- ERouting Information Protocol Version 2
- FNext Hop Resolution Protocol
How the community answered
(30 responses)- A7% (2)
- B3% (1)
- C70% (21)
- D3% (1)
- F17% (5)
Why each option
GETVPN preserves original IP headers, so existing routing protocols function without modification and no additional overlay routing protocol is required.
Running a separate OSPF process would create unnecessary routing complexity; GETVPN's header-preserving design makes an additional process entirely redundant.
EIGRP would introduce an additional routing process with no benefit, since existing routing already handles path selection and GETVPN does not disrupt it.
Unlike traditional tunnel-based VPNs, GETVPN is a tunnel-less architecture that encrypts the payload while keeping the original IP source and destination addresses intact in the outer header. Because the routing information is preserved end-to-end, the existing OSPF sessions between PE and CE routers continue to operate normally without any additional overlay routing protocol needed between group members.
eBGP is used for inter-autonomous system routing and is not appropriate or necessary as an overlay in this single-provider MPLS L3 VPN scenario.
RIPv2 offers poor scalability and slow convergence, making it unsuitable even if an additional protocol were needed.
NHRP is specific to DMVPN for dynamic spoke-to-spoke tunnel resolution and has no role in GETVPN architecture.
Concept tested: GETVPN tunnel-less header preservation eliminating overlay routing
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_getvpn/configuration/xe-16-12/sec-conn-getvpn-xe-16-12-book/sec-get-vpn.html
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