Cisco 1921 IOS 15.2T上的IP SLA

有人可以向我解释为什么我不能用最新的IOS（15.2T）在Cisco 1921上创buildIP SLA探测器。 Cisco Feature Navigator上的该路由器型号上的IOS显然可用。

Router(config)#do sh ver Cisco IOS Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.2(2)T, REL) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2011 by Cisco Systems, Inc. Compiled Tue 15-Nov-11 20:59 by prod_rel_team ROM: System Bootstrap, Version 15.0(1r)M9, RELEASE SOFTWARE (fc1) Router uptime is 3 days, 18 hours, 32 minutes System returned to ROM by reload at 15:01:02 UTC Thu Dec 15 2011 System restarted at 15:02:35 UTC Thu Dec 15 2011 System image file is "flash:c1900-universalk9-mz.SPA.152-2.T.bin" Last reload type: Normal Reload Last reload reason: Reload Command ... [snip] Router(config)#ip sla ? key-chain Use MD5 Authentication for IP SLAs Control Messages responder Enable IP SLAs Responder server IPPM server configuration 

我不忍心。 欢迎任何帮助，提前致谢。