IP Services: NTP, SNMP


  • NTP server: (global) ntp master 7 ß stratum 7
  • NTP symmetric active mode: router/switch mutually synchronizes with another NTP host, configured with ntp peer command. (global) ntp peer
  • NTP broadcast client: Listens to NTP broadcasts on the Ethernet. (int) ntp broadcast client
  • NTP client: configures, “ntp server
  • Authentication on NTP:
    • ntp authentication-key 1 md5 <name>
    • ntp authenticate
    • ntp trusted-key 1
  • under interface configure “ntp broadcast” (broadcast the time)
  • show ntp associations


  • SNMPv1: simple authentication with communities, used MIB-I
  • SNMPv2: removed requirement for communities, added GetBulk and inform messages, MIB-II
  • SNMPv2c: only difference, allowed SNMPv1 style communities with SNMPv2
  • SNMPv3: better security, backward compatibility to communities.
  • communities: read-only, read-write, trap.
  • Inform requests are acknowledged with an SNMP response packet.
  • Messages:
    • Response: responds to information in Get and Set requests.
    • Inform: A message used b/w SNMP managers to allow MIB data to be exchanged about agents they both manage.
  • MIBS:
    • RMON is outside MIB-II
  • SNMPv3 adds authentication and encryption. MD5 and SHA creates a message digest for each protocol message (authentication) and DES to encrypt messages providing encryption (privacy).
  • SNMP embedded event manager
    • automatic recovery actions are performed without need to fully reboot the routing device
    • allows event management capability directly inside the Cisco IOS devices.
    • action snmp-trap enables the traps event-manager command, also requires snmp-server configuration.
    • two types of EEM policy: applets and script
    • E.g: event manager applet IOSWD_Sample1
      • event ioswdsysmon sub1 cpu-proc taskname “task 1” op ge val 25 period 10 (triggers an applet when avg cpu usage is greater than or equat to 25% for 10 seconds. )
      • action 1.0 syslog msg “IOSWD_Sample1 Policy Triggered” (generates syslog notification)

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