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The network device must use its loopback or OOB management interface address as the source address when originating TFTP or FTP traffic.


Overview

Finding ID Version Rule ID IA Controls Severity
V-14677 NET0902 SV-15352r3_rule ECSC-1 Low
Description
Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of network devices. It is easier to construct appropriate ingress filters for management plane traffic destined to the network management subnet since the source addresses will be from the range used for loopback interfaces instead of a larger range of addresses used for physical interfaces. Log information recorded by authentication and syslog servers will record the router’s loopback address instead of the numerous physical interface addresses. TFTP and FTP messages sent to management servers should use the loopback address as the source address.
STIG Date
Perimeter L3 Switch Security Technical Implementation Guide - Cisco 2018-11-28

Details

Check Text ( C-12819r6_chk )
Review the configuration and verify a loopback interface address is used as the source address when originating TFTP or FTP traffic.

Router# show run
Building configuration...
!
!
interface Loopback0
description Loopback interface
ip address x.x.x.x 255.255.255.255
no ip directed-broadcast
!
...
ip telnet source-interface Loopback0
ip tftp source-interface Loopback0
ip ftp source-interface Loopback0

If the device is managed from an OOB management network, the OOB interface must be used instead.

Router# show run
Building configuration...
!
...
ip tftp source-interface fe0/0
ip ftp source-interface fe0/0
Fix Text (F-40461r1_fix)
Configure the network device to use a loopback interface address as the source address when originating TFTP or FTP traffic.

Example:
Router(config)# interface loopback 0
Router(config-if)# ip address x.x.x.x 255.255.255.255
Router(config)# ip ftp source-interface loopback0
Router(config)# ip tftp source-interface loopback0

If an OOB management interface is being used, configure the interface for TFTP or FTP traffic origination.

Example:
Router(config)# ip ftp source-interface fe0/0
Router(config)# ip tftp source-interface fe0/0