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V-220472

CAT II (Medium)

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

Rule ID

SV-220472r945859_rule

STIG

Cisco IOS Switch RTR Security Technical Implementation Guide

Version

V3R3

CCIs

CCI-002403

Discussion

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.

Check Content

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

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