186 CHAPTER 4: R OUTER COMMAND REFERENCEshow icmp counters Displays input and output counters for ICMP messages.Traceroute-generated packets received by the RAS 1500 do notincrement the ICMP error counts Time Exceeded and DestinationUnreachable. Also, a number of ICMP error messages are sent to SYSLOGhosts. The Receive Destination Unreachable event is sent to the console.It lists the following:INPUT COUNTERSn Messages — ICMP packets received.n Errors — ICMP packets received with errors.n Destination Unreachable — Sum of ICMP messages received when arouter cannot forward a packet to its specified destination. Errormessages are sent to the console and CLI.n Time Exceeded — Sum of ICMP messages generated by a router whentime has exceeded or a timeout has occurred while waiting for apacket segment. Error messages sent to SYSLOG host.n Parameter Problems — Sum of ICMP messages generated by a routerwhen it encounters an error. Error messages sent to SYSLOG host.n Source Quench — Sum of ICMP messages informing a host it shouldslow data transmission to ease congestion. Error messages sent toSYSLOG host.n Redirects — Sum of ICMP messages concerning a router advertising ahost of a better next hop. Error messages not logged.n Echos — Sum of ICMP request messages received, signifying transportsystem success.n Echo Replies — Sum of ICMP reply messages received, indicatingtransport system success.n Timestamps — Sum of ICMP request messages received seeking timefrom another machine for clock synchronization and estimated transittime purposes. Error messages sent to SYSLOG host.n Timestamp Replies — Sum of ICMP timestamp reply messages.ICMP SETTINGSICMP Logging: ENABLEDICMP Router Advertise:Enabled ENABLED
