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Cisco Bug: CSCsz71831 - interface queue wedged by malformed IP pak with prot number 53

Last Modified

Jan 29, 2017

Products (1)

  • Cisco IOS

Known Affected Releases

12.4(23c) 12.4(24.6)PI11n 12.4(24.6)T8

Description (partial)

An interface may hold several DNS packets in the interface buffers, and not be released till an upgrade
of the device.

Has only been observed on low end router systems, which are configured to listen on TCP/UDP port 53 (DNS).

Affected configurations would include any configuration that has either:
ip dns server
ip dns spoofing
ip dns primary

and can be verified the device is listening via "show udp", "show ip socket" or "show tcp brief all"

It is not possible to wedge the entire interface, to cause a DoS, but around half the interface buffers
may be consumed.
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