A network administrator at an enterprise branch office is troubleshooting an unsynchronized NTP client on a Cisco router named Branch-R1. The router has IP reachability to an authoritative internal time server at IP address , but security firewalls along the transit path strictly enforce access rules that permit management services only if they originate from Branch-R1's dedicated Loopback0 interface (). Currently, NTP packets generated by the router are dropped by the firewall because they use the egress physical interface IP address as their source. Which global configuration command must be configured on Branch-R1 to force all outgoing NTP traffic to originate from the specified loopback interface?
- ntp source Loopback0Answer
- Bip helper-address 10.50.1.10
- Cntp peer 10.50.1.10
- Dntp master 16
Answer
The command 'ntp source Loopback0' forces the router to use the IP address of interface Loopback0 as the source IP address in all outgoing NTP packets.
The correct option specifies 'ntp source Loopback0'. In Cisco IOS, outgoing NTP packets by default derive their source IP address from the outbound interface used to reach the destination. When security appliances require management traffic to originate from a consistent logical interface (such as a loopback interface), the global configuration command 'ntp source <interface>' forces the router to place that interface's IP address into the source field of all generated NTP packets.
Step-by-Step Solution
Key Concept
NTP Source Interface Configuration