CAS-002 Question #121: Real Exam Question with Answer & Explanation

An administrator receives reports that the network is running slow for users connected to a certain switch. Viewing the network traffic, the administrator reviews the following: 18:51:59.042108 IP linuxwksta.55467 > dns.company.com.domain: 39462+ PTR? 222.17.4.10.in-addr.arpa. (42) 18:51:59.055732 IP dns.company.com.domain > linuxwksta.55467: 39462 NXDomain 0/0/0 (42) 18:51:59.055842 IP linuxwksta.48287 > dns.company.com.domain: 46767+ PTR? 255.19.4.10.in-addr.arpa. (42) 18:51:59.069816 IP dns.company.com.domain > linuxwksta.48287: 46767 NXDomain 0/0/0 (42) 18:51:59.159060 IP linuxwksta.42491 > 10.4.17.72.iscsi-target: Flags [P.], seq 1989625106:1989625154, ack 2067334822, win 1525, options [nop,nop,TS val 16021424 ecr 215646227], length 48 18:51:59.159145 IP linuxwksta.48854 > dns.company.com.domain: 3834+ PTR? 72.17.4.10.in-addr.arpa. (41) 18:51:59.159314 IP 10.4.17.72.iscsi-target > linuxwksta.42491: Flags [P.], seq 1:49, ack 48, win 124, options [nop,nop,TS val 215647479 ecr 16021424], length 48 18:51:59.159330 IP linuxwksta.42491 > 10.4.17.72.iscsi-target: Flags [.], ack 49, win 1525, options [nop,nop,TS val 16021424 ecr 215647479], length 0 18:51:59.165342 IP dns.company.com.domain > linuxwksta.48854: 3834 NXDomain 0/0/0 (41) 18:51:59.397461 ARP, Request who-has 10.4.16.58 tell 10.4.16.1, length 46 18:51:59.397597 IP linuxwksta.37684 > dns.company.com.domain: 15022+ PTR? 58.16.4.10.in-addr.arpa. (41) Given the traffic report, which of the following is MOST likely causing the slow traffic?