The router must use its loopback or OOB management interface address as the source address when originating TACACS+ or RADIUS traffic.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-14672	NET0897	SV-16092r2_rule		Low

Description
Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router 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. TACACS+, RADIUS messages sent to management servers should use the loopback address as the source address.

Description

Using a loopback address as the source address offers a multitude of uses for security, access, management, and scalability of routers. It is easier to construct appropriate ingress filters for router 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. TACACS+, RADIUS messages sent to management servers should use the loopback address as the source address.

STIG	Date
Perimeter Router Security Technical Implementation Guide Juniper	2018-02-27

Details

Check Text ( C-13849r3_chk )
Review the configuration and verify the loopback interface address is used as the source address when originating TACACS+ or RADIUS traffic. If the device is managed from an OOB management network, the OOB interface must be used instead. Step 1: Verify that a loopback address has been configured with an IP address. The configuration should look similar to the following: interfaces { lo0 { unit 0 { family inet { address 10.10.2.1/32; } } } Note: Only one loopback interface can be configured on JUNOS routers; however, multiple addresses can be defined. Step 2: Verify that TACACS+ and RADIUS are configured to use the loopback address by comparing the source address defined for tacplus-server and radius-server with the address configured for the loopback interface. You should find a configuration similar to the examples below: TACACS+ system { tacplus-server { 10.10.2.11; source-address 10.10.2.1; } } RADIUS system { radius-server { 10.10.2.21; source-address 10.10.2.1; } } Note: If source-address is not specified, then the default-address-selection under system hierarchy must be configured. Configuring system default-address-selection will enable the router to use the loopback interface as the source address for most locally generated IP packets. This configuration would appear as follows: system { default-address-selection; … } }

Check Text ( C-13849r3_chk )

Review the configuration and verify the loopback interface address is used as the source address when originating TACACS+ or RADIUS traffic. If the device is managed from an OOB management network, the OOB interface must be used instead.

Step 1: Verify that a loopback address has been configured with an IP address. The configuration should look similar to the following:

interfaces {
lo0 {
unit 0 {
family inet {
address 10.10.2.1/32;
}
}
}

Note: Only one loopback interface can be configured on JUNOS routers; however, multiple addresses can be defined.

Step 2: Verify that TACACS+ and RADIUS are configured to use the loopback address by comparing the source address defined for tacplus-server and radius-server with the address configured for the loopback interface. You should find a configuration similar to the examples below:

TACACS+

system {
tacplus-server {
10.10.2.11;
source-address 10.10.2.1;
}
}

RADIUS

system {
radius-server {
10.10.2.21;
source-address 10.10.2.1;
}
}

Note: If source-address is not specified, then the default-address-selection under system hierarchy must be configured. Configuring system default-address-selection will enable the router to use the loopback interface as the source address for most locally generated IP packets. This configuration would appear as follows:

system {
default-address-selection;
…
}
}

Fix Text (F-14134r5_fix)
Configure the device to use its loopback or OOB management interface address as the source address when originating authentication services traffic.