CiscoCISCO Adv. Routing Services (ENARSI) 300-410 Certification·EN·Updated 16 Aug 2026
Router_A's ip summary-address eigrp 1 172.16.80.0 255.255.240.0 isn't being advertised to Router_B. Which Router_A loopback address ensures the summary is advertised?
Choose an answer
Tap an option to check your answer.
Correct answer: interface loopback 0 ; ip address 172.16.81.1 255.255.255.0 ; interface Ethernet0 ; ip address 192.168.3.1 255.255.255.0 ; ip summary-address eigrp 1 172.16.80.0 255.255.240.0.
Why this is the answer
EIGRP requires a component network within the summary range to be present in the routing table for the summary route to be advertised. The summary address 172.16.80.0 255.255.240.0 covers the range from 172.16.80.0 to 172.16.95.255. The correct option, ip address 172.16.81.1 255.255.255.0, falls within this summary range, ensuring the summary is advertised.
The incorrect options 172.18.81.1, 172.16.79.1, and 172.16.96.1 are outside the specified summary range (172.16.80.0 - 172.16.95.255). Therefore, if these were the only networks on RouterA, the EIGRP summary route would not be advertised.