The Cisco perimeter switch must be configured to block all packets with any IP options.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-220472	CISC-RT-000350	SV-220472r622190_rule		Medium

Description

Packets with IP options are not fast switched and henceforth 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 IOS Switch RTR Security Technical Implementation Guide	2021-03-19

Details

Check Text ( C-22187r508489_chk )
Review the switch configuration to determine if it will block all packets with IP options. ip access-list extended EXTERNAL_ACL permit tcp any any established deny ip any any option any-options permit … … … … deny ip any any log-input If the switch is not configured to drop all packets with IP options, this is a finding.

Fix Text (F-22176r508490_fix)
Configure the switch to drop all packets with IP options. SW1(config)#ip access-list extended EXTERNAL_ACL SW1(config-ext-nacl)#15 deny ip any any option any-options