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The Cisco PE switch must be configured to ignore or drop all packets with any IP options.


Overview

Finding ID Version Rule ID IA Controls Severity
V-221128 CISC-RT-000750 SV-221128r622190_rule Medium
Description
Packets with IP options are not fast-switched and therefore must be punted to the switch processor. Hackers who initiate denial-of-service (DoS) attacks on switches commonly send large streams of packets with IP options. Dropping the packets with IP options reduces the load of IP options packets on the switch. The end result is a reduction in the effects of the DoS attack on the switch and on downstream switches.
STIG Date
Cisco NX-OS Switch RTR Security Technical Implementation Guide 2021-03-29

Details

Check Text ( C-22843r409873_chk )
In Cisco NX-OS, all packets with any header option other than the “source-route” header option are dropped. By default, ipv4 source routing is enabled. Verify that source routing is disabled via the following command:

no ip source-route

If the switch is not configured to drop all packets with IP option source routing, this is a finding.
Fix Text (F-22832r409874_fix)
Configure the switch to drop all packets with IP option source routing.

SW1(config)# no ip source-route
SW1(config)# end