400-007 · Question #104
Company XYZ is running OSPF in their network. They have merged with another company that is running EIGRP as the routing protocol. Company XYZ now needs the two domains to talk to each other with…
The correct answer is B. multipoint route-redistribution with route filtering using route tags. Multipoint redistribution with route tags satisfies all requirements by using multiple ASBRs for redundancy, route tags for automatic loop prevention, and a tag-based filter policy that scales without manual updates when new networks are added.
Question
Company XYZ is running OSPF in their network. They have merged with another company that is running EIGRP as the routing protocol. Company XYZ now needs the two domains to talk to each other with redundancy, while maintaining a loop free environment. The solution must scale when new networks are added into the network in the near future. Which technology can be used to meet these requirements?
Options
- Amultipoint route-redistribution with route filtering using ACLs
- Bmultipoint route-redistribution with route filtering using route tags
- Csingle point route-redistribution with route filtering using route tags
- Dsingle point route-redistribution with route filtering using ACLs
How the community answered
(27 responses)- A4% (1)
- B70% (19)
- C7% (2)
- D19% (5)
Why each option
Multipoint redistribution with route tags satisfies all requirements by using multiple ASBRs for redundancy, route tags for automatic loop prevention, and a tag-based filter policy that scales without manual updates when new networks are added.
ACL-based filtering requires an explicit permit or deny entry for each network prefix, meaning every new network added to either domain requires manual ACL updates on all redistribution points, making this solution difficult to scale as stated in the requirements.
Multipoint redistribution places ASBRs at multiple points between the OSPF and EIGRP domains for redundancy, and route tags automatically mark redistributed routes so that a deny filter on the receiving side prevents re-redistribution back into the originating domain, eliminating routing loops. Because new networks inherit the same tag policy automatically, the solution scales without requiring any ACL modifications when new prefixes are added.
Single-point redistribution uses only one ASBR to connect the two routing domains, creating a single point of failure that does not meet the explicit requirement for redundancy between the OSPF and EIGRP domains.
Single-point redistribution fails the redundancy requirement, and ACL-based filtering also fails the scalability requirement because new network prefixes require manual ACL updates rather than being handled automatically by a tag-based policy.
Concept tested: Mutual redistribution loop prevention and scalability using route tags
Source: https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8606-redist.html
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