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Cisco Bug: CSCuj28158 - tcp adjust-mss incorrectly done after in2out NAT for tcp_syn pkts

Last Modified

Apr 17, 2019

Products (1)

  • Cisco IOS

Known Affected Releases

15.2(4)M4.3

Description (partial)

Symptom:
Usage of egress "ip tcp adjust-mss" on output Tunnel seems changes the Features order of operation for TCP SYN packets.
NAT Inside-to-Outside gets performed on it first and only then ingress ACL and PBR,
which are acting on already nat translated src_ipv4.

So because of this on latest code the ACL and PBR need to include both src_ip allowed  - before and after nat.
Otherwise, the tcp_syn gets dropped.

Conditions:
ip tcp-adjast+nat+pbr used ingress
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