200-101 · Question #51
Refer to the exhibit. Given the output from the show ip eigrp topology command, which router is the feasible successor?
The correct answer is B. 10.0.0.2 (Serial0.1), from 10.0.0.2, Send flag is 0x0 Composite metric is (53973248/128256), Route is Internal Vector metric: Minimum bandwidth is 48 Kbit Total delay is 25000 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 1. In EIGRP, the feasible successor is a backup route that satisfies the Feasibility Condition (FC): the neighbor's Reported Distance (RD) must be strictly less than the local router's current Feasible Distance (FD) to the destination. First, identify the successor - the route with
Question
Options
- A10.1.0.3 (Serial0), from 10.1.0.3, Send flag is 0x0 Composite metric is (46866176/46354176), Route is Internal Vector metric: Minimum bandwidth is 56 Kbit Total delay is 45000 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 2
- B10.0.0.2 (Serial0.1), from 10.0.0.2, Send flag is 0x0 Composite metric is (53973248/128256), Route is Internal Vector metric: Minimum bandwidth is 48 Kbit Total delay is 25000 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 1
- C10.1.0.1 (Serial0), from 10.1.0.1, Send flag is 0x0 Composite metric is (46152000/41640000), Route is Internal Vector metric: Minimum bandwidth is 64 Kbit Total delay is 45000 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 2
- D10.1.1.1 (Serial0.1), from 10.1.1.1, Send flag is 0x0 Composite metric is (46763776/46251776), Route is External Vector metric: Minimum bandwidth is 56 Kbit Total delay is 41000 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 2
How the community answered
(27 responses)- A11% (3)
- B63% (17)
- C22% (6)
- D4% (1)
Explanation
In EIGRP, the feasible successor is a backup route that satisfies the Feasibility Condition (FC): the neighbor's Reported Distance (RD) must be strictly less than the local router's current Feasible Distance (FD) to the destination. First, identify the successor - the route with the lowest composite metric (FD). That is option C with FD=46,152,000. Now check each remaining route's RD against 46,152,000: Option A has RD=46,354,176 (exceeds FC), Option B has RD=128,256 (satisfies FC), Option D has RD=46,251,776 (exceeds FC). Option B is the only route that passes the feasibility condition, making it the feasible successor. Its very low RD (128,256) indicates a short path reported by that neighbor, even though its total FD (53,973,248) is higher than the successor's.
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