The Cisco perimeter router must be configured to have Link Layer Discovery Protocol (LLDP) disabled on all external interfaces.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-216764	SRG-NET-000364-RTR-000111	CISC-RT-000360	SV-216764r856442_rule	2024-08-22	3

Description
LLDP is a neighbor discovery protocol used to advertise device capabilities, configuration information, and device identity. LLDP is media- and protocol-independent as it runs over layer 2; therefore, two network nodes that support different layer 3 protocols can still learn about each other. Allowing LLDP messages to reach external network nodes provides an attacker a method to obtain information of the network infrastructure that can be useful to plan an attack.

Description

LLDP is a neighbor discovery protocol used to advertise device capabilities, configuration information, and device identity. LLDP is media- and protocol-independent as it runs over layer 2; therefore, two network nodes that support different layer 3 protocols can still learn about each other. Allowing LLDP messages to reach external network nodes provides an attacker a method to obtain information of the network infrastructure that can be useful to plan an attack.

ℹ️ Check
This requirement is not applicable for the DODIN Backbone. Step 1: Verify LLDP is not enabled globally via the command lldp By default LLDP is not enabled globally. If LLDP is enabled, proceed to step 2. Step 2: Verify LLDP transmit is disabled on any external interface as shown in the example below. interface GigabitEthernet0/0/0/1 ipv4 address x.1.34.3 255.255.255.252 lldp transmit disable Note: LLDP is enabled by default on all interfaces once it is enabled globally; hence the commands lldp transmit and lldp receive will not be visible on the interface configuration. If LLDP transmit is enabled on any external interface, this is a finding.

ℹ️ Check

This requirement is not applicable for the DODIN Backbone. Step 1: Verify LLDP is not enabled globally via the command lldp By default LLDP is not enabled globally. If LLDP is enabled, proceed to step 2. Step 2: Verify LLDP transmit is disabled on any external interface as shown in the example below. interface GigabitEthernet0/0/0/1 ipv4 address x.1.34.3 255.255.255.252 lldp transmit disable Note: LLDP is enabled by default on all interfaces once it is enabled globally; hence the commands lldp transmit and lldp receive will not be visible on the interface configuration. If LLDP transmit is enabled on any external interface, this is a finding.

✔️ Fix
Disable LLDP transmit on all external interfaces as shown in the example below. RP/0/0/CPU0:R3(config)#interface g0/0/0/1 RP/0/0/CPU0:R3(config-if)#lldp transmit disable