Cisco
300-415 · Question #38
300-415 Question #38: Real Exam Question with Answer & Explanation
The correct answer is D: Set same overlay AS on both DC WAN Edge routers. When redistributing routes between OMP and BGP at two Data Center sites with a direct interlink, setting the same overlay AS on both DC WAN Edge routers prevents learning duplicate routes from the LAN.
Architecture
Question
When redistribution is configured between OMP and BGP at two Data Center sites that have Direct Connection Interlink, which step avoids learning the same routes on WAN Edge routers of the DCs from LAN?
Options
- ASet down-bit on Edge routers on DC1
- BDefine different VRFs on both DCs
- CSet OMP admin distance lower than BGP admin distance
- DSet same overlay AS on both DC WAN Edge routers
Explanation
When redistributing routes between OMP and BGP at two Data Center sites with a direct interlink, setting the same overlay AS on both DC WAN Edge routers prevents learning duplicate routes from the LAN.
Common mistakes.
- A. The 'down-bit' prevents redistribution of underlay routes back into the same VPN via OMP, which is different from preventing loops when redistributing between OMP and BGP across two DC sites.
- B. Defining different VRFs would segment traffic but would not inherently prevent routes from being redistributed and learned redundantly if the redistribution policy allows it.
- C. Setting OMP admin distance lower than BGP influences route preference on the local router but does not prevent the advertisement of routes that could lead to a loop across the interlink.
Concept tested. OMP and BGP redistribution loop prevention
Topics
#SD-WAN Routing#OMP#BGP Redistribution#Loop Prevention#Multi-DC Design
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