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


Finding ID Version Rule ID IA Controls Severity
V-221016 CISC-RT-000360 SV-221016r856411_rule Low
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.
Cisco IOS XE Switch RTR Security Technical Implementation Guide 2023-09-13


Check Text ( C-22731r408842_chk )
Step 1: Verify LLDP is not enabled globally via the command.

lldp run

By default LLDP is not enabled globally. If LLDP is enabled, proceed to Step 2.

Step 2: Verify LLDP is not enabled on any external interface as shown in the example below:

interface GigabitEthernet0/1
ip address x.1.12.1
no lldp transmit

Note: LLDP is enabled by default on all interfaces once it is enabled globally; hence the command "lldp transmit" will not be visible on the interface configuration.

If LLDP transmit is enabled on any external interface, this is a finding.
Fix Text (F-22720r408843_fix)
Disable LLDP transmit on all external interfaces as shown in the example below:

SW1(config)#int g0/1
SW1(config-if)#no lldp transmit