This command is mostly used when you are speaking with Cisco TAC. It displays a lot of information about your device.
Below is an example of show tech-support.
R2#show tech-support —————— show version —————— Cisco IOS Software, 3600 Software (C3640-JK9S-M), Version 12.4(16), RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2007 by Cisco Systems, Inc. Compiled Wed 20-Jun-07 11:43 by prod_rel_team ROM: ROMMON Emulation Microcode ROM: 3600 Software (C3640-JK9S-M), Version 12.4(16), RELEASE SOFTWARE (fc1) R2 uptime is 19 minutes System returned to ROM by unknown reload cause – suspect boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19 System image file is “tftp://255.255.255.255/unknown” This product contains cryptographic features and is subject to United States and local country laws governing import, export, transfer and use. Delivery of Cisco cryptographic products does not imply third-party authority to import, export, distribute or use encryption. Importers, exporters, distributors and users are responsible for compliance with U.S. and local country laws. By using this product you agree to comply with applicable laws and regulations. If you are unable to comply with U.S. and local laws, return this product immediately. A summary of U.S. laws governing Cisco cryptographic products may be found at: http://www.cisco.com/wwl/export/crypto/tool/stqrg.html If you require further assistance please contact us by sending email to email@example.com. Cisco 3640 (R4700) processor (revision 0xFF) with 124928K/6144K bytes of memory. Processor board ID 00000000 R4700 CPU at 100MHz, Implementation 33, Rev 1.2 2 FastEthernet interfaces DRAM configuration is 64 bits wide with parity enabled. 125K bytes of NVRAM. 8192K bytes of processor board System flash (Read/Write) Configuration register is 0x2102 —————— show running-config —————— Building configuration… Current configuration : 1336 bytes SOME OUTPUT REMOVED —————— show crypto ipsec profile —————— —————— show crypto isakmp sa —————— dst src state conn-id slot status —————— show crypto engine connection active —————— ID Interface IP-Address State Algorithm Encrypt Decrypt —————— show crypto ipsec sa —————— No SAs found