When redistributing routes between OSPF and EIGRP on a single router, which technique helps prevent redistribution loops?

When redistributing routes between OSPF and EIGRP on a single router, which technique helps prevent redistribution loops?

• A. Tag routes to prevent re-redistribution loops
• B. Enable redistribution with route-maps to control metrics
• C. Monitor administrative distance and ensure proper route selection
• D. Disable redistribution entirely

Answer: (A)

Preventing redistribution loops between OSPF and EIGRP relies on tagging redistributed routes. When a route is moved from one protocol to the other, you attach a tag to that route. Then the reverse redistribution is filtered to ignore any routes that already carry that tag. This way a route learned from OSPF and redistributed into EIGRP won’t be re-redistributed back into OSPF, breaking the potential loop while still allowing initial redistribution to occur. Practically, you configure a route-map on the redistribution process to set a tag on the redistributed routes, and you filter the opposite direction by denying routes with that tag. Other methods don’t inherently prevent loops: adjusting metrics affects path choice but not the loop mechanism, administrative distance controls preference rather than loop avoidance, and disabling redistribution eliminates the capability altogether.

Preventing redistribution loops between OSPF and EIGRP relies on tagging redistributed routes. When a route is moved from one protocol to the other, you attach a tag to that route. Then the reverse redistribution is filtered to ignore any routes that already carry that tag. This way a route learned from OSPF and redistributed into EIGRP won’t be re-redistributed back into OSPF, breaking the potential loop while still allowing initial redistribution to occur. Practically, you configure a route-map on the redistribution process to set a tag on the redistributed routes, and you filter the opposite direction by denying routes with that tag.

Other methods don’t inherently prevent loops: adjusting metrics affects path choice but not the loop mechanism, administrative distance controls preference rather than loop avoidance, and disabling redistribution eliminates the capability altogether.