I am using IPM 4.1 with ICMP-Echo to monitor C1841 ( IOS 12.4(20)T ). But the monitor is always fail. Using snmp browser tools, i find that oid "rttMonEchoAdminTargetAddress" value is "00:00:00:00". But before IOS 12.4(20)T, "rttMonEchoAdminTargetAddress" value should be icmp-echo target ip address. Does anyone has solution on this problem? Thanks!