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Cisco Bug: CSCvt43967 - Pad packets received from RA tunnel which are less than or equal 46 bytes in length with zeros

Last Modified

Sep 17, 2020

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases


Description (partial)

TCP ACK packets from a Windows AnyConnect client have non-zero padding bytes which the receiving server is dropping causing the SCP file transfer to stall while the server times out and the client is forced to resend the ACK (this time with options, making the frame larger than the minimum size).

Cisco Firepower 4100 running FXOS 2.6.1 and ASA release as a VPN concentrator with Windows AnyConnect client connecting.
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