Interface monitoring in EEM
EEM (Embedded Event Manager) is quite nice feature on IOS platforms allowing administrator to configure router behavior during predefined events. Usually it’s connected with IP SLA – if probes returns negative value appropriate applet is executed. But EEM itself can be used for deeper interface and link monitoring than IP SLA allows with it’s probes
IP SLA can send ie. ICMP probes and basing on predefined timeouts and thresholds it returns positive or negative result. But not always when link is working incorrectly pings will be lost or high RTT will be observed. Also our ping might just be lucky to pass link properly while customers traffic will suffer. Building reliable probes with IP SLA might be hard.
EEM itself offers other way of monitoring interface behaviors using same counters one can see on show interface output. You can monitor wide range of interfaces, unfortunately not E1 directly. List of parameters you can monitor includes all interface counters
TEST-3G(config-applet)#event interface name FastEthernet 0/0 parameter ? input_errors Number of damaged packets received input_errors_crc Number of packets received with CRC errors input_errors_frame Number of framing ERR packets received input_errors_overrun Number of overruns and resource errors input_packets_dropped Number of packets dropped from input Q interface_resets Number of times an interface has been reset output_buffer_failures Number of failed buffers output_buffer_swappedout Number of packets swapped to DRAM output_errors Number of packets errored on output output_errors_underrun Number of underruns on output output_packets_dropped Number of packets dropped from output Q receive_broadcasts Number of broadcast packets received receive_giants Number of too large packets received receive_rate_bps Interface receive rate in bits/sec receive_rate_pps Interface receive rate in pkts/sec receive_runts Number of too small packets received receive_throttle Number of times the receiver was disabled reliability Interface reliability as a fraction of 255 rxload Receive rate as a fraction of 255 transmit_rate_bps Interface transmit rate in bits/sec transmit_rate_pps Interface transmit rate in pkts/sec txload Transmit rate as a fraction of 255
Monitoring is done in time intervals. In following example if during one second time interval input_errors counter increases by at least 10 defined action will be executed
event manager applet testSerial event interface name Serial0/0:15 parameter input_errors entry-op ge entry-val 10 entry-type increment exit-op le exit-val 1 exit-type increment poll-interval 10 action 1.0 cli command "ping 10.199.0.2 repeat 1"
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