A network administrator is troubleshooting remote administration access to an edge router (). Systems engineers on the management network () report that ping requests to the router succeed, but SSH connections to port 22 time out. Upon inspecting the router interface's inbound Access Control List (ACL), the administrator reviews the following entries:
access-list 105 permit icmp 10.40.8.0 0.0.0.255 any
access-list 105 permit udp 10.40.8.0 0.0.0.255 host 172.28.10.1 eq 22
access-list 105 deny ip any any
Which of the following is the root cause preventing SSH access to the router?
- The ACL rule specifies UDP port 22 instead of TCP port 22, causing SSH traffic to match the deny rule.Cevap
- BThe ACL rule permits ICMP traffic, which automatically overrides TCP and UDP traffic on the same interface.
- CThe management workstations and the router reside on different IP subnets without a VLAN trunk.
- DThe workstations require a direct Layer 2 broadcast domain connection to establish SSH management sessions.
Cevap
The ACL rule specifies UDP port 22 instead of TCP port 22, causing incoming SSH packets to be dropped by the final deny statement.
SSH utilizes TCP as its transport protocol on port 22. The configured ACL rule permits UDP port 22, causing TCP SSH initiation packets to skip the permit statement and trigger the subsequent explicit deny rule.
Adım Adım Çözüm
Anahtar Kavram
ACL Transport Protocol Matching (TCP vs UDP)
Tahmini Süre:1m 30s