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


Overview

Finding ID Version Rule ID IA Controls Severity
V-96567 CISC-RT-000350 SV-105705r1_rule Medium
Description
Packets with IP options are not fast switched and henceforth must be punted to the router processor. Hackers who initiate denial-of-service (DoS) attacks on routers commonly send large streams of packets with IP options. Dropping the packets with IP options reduces the load of IP options packets on the router. The end result is a reduction in the effects of the DoS attack on the router and on downstream routers.
STIG Date
Cisco IOS Router RTR Security Technical Implementation Guide 2019-12-20

Details

Check Text ( C-95403r1_chk )
This requirement is not applicable for the DODIN Backbone.

Review the router 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 router is not configured to drop all packets with IP options, this is a finding.
Fix Text (F-102241r1_fix)
This requirement is not applicable for the DODIN Backbone.

Configure the router to drop all packets with IP options.

R1(config)#ip access-list extended EXTERNAL_ACL
R1(config-ext-nacl)#15 deny ip any any option any-options