Cisco PSIRT obtained further information from NCNIPC (China) about how
the testing of the reported vulnerabilities was performed.
Cisco PSIRT can confirm that no new vulnerabilities have been
discovered. The Cisco 2911 Integrated Services Router (ISR) that was used to
perform testing had no control plane protection configured, which Cisco
recommends as a best practice. The Cisco 2911 ISR was tested by sending large
amounts of untrusted traffic to an infrastructure address. The device has to
process switch these packets and reply with an ICMP unreachable message (rate
limited based on the ip icmp rate-limit unreachable
configuration command), which increases CPU utilization.
Cisco has performed testing on the Cisco ISR range of products, and the
devices can handle such attacks if proper control plane protection is
configured. Cisco PSIRT recommends configuring control plane protection as a
best practice. This protection mechanism is outlined in the document "Cisco
Guide to Harden Cisco IOS Devices", which is available from the following
Best practices indicate that network administrators should identify
traffic that should never be allowed to target infrastructure devices and block
that traffic at the border of networks and on individual devices using
hardening configuration features like infrastructure access control lists
(iACLs), receive access control lists (rACLs), Control Plane Policing (CoPP),
and Modular Quality of Service (QoS) Command-Line Interface (MQC).