Preview Tool

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


Description (partial)

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.

ip tcp-adjast+nat+pbr used ingress
Bug details contain sensitive information and therefore require a account to be viewed.

Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
  • Severity
  • Known Fixed Releases
  • Related Community Discussions
  • Number of Related Support Cases
Bug information is viewable for customers and partners who have a service contract. Registered users can view up to 200 bugs per month without a service contract.