3.2.4 Disable IP Directed Broadcasts on all Layer 3 Interfaces

Information

An IP directed broadcast is an IP packet whose destination address is a valid broadcast address for an IP subnet, but which originates from a node that is not itself a part of that destination subnet.

Rationale:

Directed broadcasts can be abused in several ways:

a volumetric DOS attack against the NX-OS switch itself, the sent volume of data can be much larger than the received request

a volumetric DOS attack against a third party (often called a 'smurf attack')

a single-packet reconnaissance of a local subnet

We recommend that you disable the ip directed-broadcast command on any interface where they are not required for some reason.

Solution

switch(config-if)# no ip directed-broadcast

See Also

https://workbench.cisecurity.org/benchmarks/6524

Item Details

Category: ACCESS CONTROL, CONFIGURATION MANAGEMENT, CONTINGENCY PLANNING, PLANNING, PROGRAM MANAGEMENT, SYSTEM AND SERVICES ACQUISITION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|AC-18, 800-53|AC-18(1), 800-53|AC-18(3), 800-53|CM-2, 800-53|CM-6, 800-53|CM-7, 800-53|CM-7(1), 800-53|CM-9, 800-53|CP-6, 800-53|CP-7, 800-53|PL-8, 800-53|PM-7, 800-53|SA-8, 800-53|SC-7, CSCv7|11

Plugin: Cisco

Control ID: 1deacabc939f9ec0dda2d556272716a5e31a75b2c0a6626c5c29d7269a3fd5d8