This document provides information about Adaptive Security Appliance (ASA) TCP connection flags.
Note: The content in this document was created by Jay Johnston, Cisco TAC Engineer.
Readers of this document should have knowledge of these topics.
Basic knowledge of the TCP Communications Protocol
Basic knowledge of the ASA Command Line (CLI)
The information in this document is based on ASA version 8.4.
For more information on document conventions, refer to Cisco Technical TipsConventions.
When troubleshooting TCP connections through the ASA, the connection flags shown for each TCP connection provide a wealth of information about the state of TCP connections to the ASA. This information can be used to troubleshoot problems with the ASA, as well as problems elsewhere in the network.
Here is the output of the show conn protocol tcp command, which shows the state of all TCP connections through the ASA. These connections can also be seen with the show conn command.
ASA# show conn protocol tcp 101 in use, 5589 most used TCP outside 10.23.232.59:5223 inside 192.168.1.3:52419, idle 0:00:11, bytes 0, flags saA TCP outside 192.168.3.5:80 dmz 172.16.103.221:57646, idle 0:00:29, bytes 2176, flags UIO TCP outside 10.23.232.217:5223 inside 192.168.1.3:52425, idle 0:00:10, bytes 0, flags saA TCP outside 10.23.232.217:443 inside 192.168.1.3:52427, idle 0:01:02, bytes 4504, flags UIO TCP outside 10.23.232.57:5223 inside 192.168.1.3:52412, idle 0:00:23, bytes 0, flags saA TCP outside 10.23.232.116:5223 inside 192.168.1.3:52408, idle 0:00:23, bytes 0, flags saA TCP outside 10.23.232.60:5223 inside 192.168.1.3:52413, idle 0:00:23, bytes 0, flags saA TCP outside 10.23.232.96:5223 inside 192.168.1.3:52421, idle 0:00:11, bytes 0, flags saA TCP outside 10.23.232.190:5223 inside 192.168.1.3:52424, idle 0:00:10, bytes 0, flags saA
The next picture shows the ASA TCP Connection flags at different stages of the TCP state machine. The connection flags can be seen with the show conn command on the ASA.
Additionally, in order to view all of the possible connection flags issue the show connection detail command on the command line:
ASA# show conn detail 84 in use, 1537 most used Flags: A - awaiting inside ACK to SYN, a - awaiting outside ACK to SYN, B - initial SYN from outside, b - TCP state-bypass or nailed, C - CTIQBE media, D - DNS, d - dump, E - outside back connection, F - outside FIN, f - inside FIN, G - group, g - MGCP, H - H.323, h - H.225.0, I - inbound data, i - incomplete, J - GTP, j - GTP data, K - GTP t3-response k - Skinny media, M - SMTP data, m - SIP media, n - GUP O - outbound data, P - inside back connection, p - Phone-proxy TFTP connection, q - SQL*Net data, R - outside acknowledged FIN, R - UDP SUNRPC, r - inside acknowledged FIN, S - awaiting inside SYN, s - awaiting outside SYN, T - SIP, t - SIP transient, U - up, V - VPN orphan, W - WAAS, X - inspected by service module
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