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-221095
CISC-RT-000350
SV-221095r999704_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.
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-22799r409775_fix)
Configure the switch to drop all packets with IP option source routing.