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Cisco Bug: CSCul10167 - 7201 15.2(4)M4 -- ZBF resets TCP conn with "ip tcp adjust-mss"

Last Modified

Jan 30, 2017

Products (1)

  • Cisco 7200 Series Routers

Known Affected Releases

15.1(4)M5.9 15.2(4)M4.5

Description (partial)

Symptom: When the <CmdBold>ip tcp adjust-mss<noCmdBold> command is applied to ZBF interface, it can happened that firewall create two sessions for the same flow. The second session is created for the same SYN packet and no further packets are matched to it, so it stays as embryonic.
When the embryonic timer expire (30 sec), then firewall removes both connections from the table and sends TCP RST to both speakers.
Conditions: The issue was discovered on Cisco 7201 platform for Cisco IOS Release 15.2(4)M4 and 15.1(4)M5 when the <CmdBold>ip tcp adjust-mss<noCmdBold> command is applied to ZBF interface.
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