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Cisco Bug: CSCuo37960 - ASA does not adjust MTU of TCP connections with IPv6 "packet too big"

Last Modified

Aug 31, 2020

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases

9.1(4) 9.3(3)

Description (partial)

ASA does not adjust MTU of  TCP sessions generated to or from the ASA itself with an IPv6  "Packet too big" packet.

Connections such as HTTPS, SSL or SSH could be affected by this problem.

This issue happens when a router between ASA and a client device has smaller MTU than ASA and a client.
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