IP SLA

  1. IP SLA
  2. Track

IP SLA

  • track:
    • state: up, if return code = OK
    • reachability: up, if return code = OK or OverThreshold
  • UDP 1967: control packets, destination port
    • can process several sessions
    • measurement
  • timestamp
    • NTP is needed for correct timestamping
    • set on interrupt
    • stamped twice on ingress and egress from device – account for processing time
(config)# ip sla auto endpoint-list type ip <LISTNAME>
(config-epl)# ip-address <IP> port <PORT>
(config)# ip sla <N>
(config-ip-sla)# udp-jitter <IP> <PORT>

; 60s default
(config-ip-sla-jitter)# frequency <sec>

; 5000 ms default
(config-ip-sla-jitter)# timeout <ms>

; 28 bytes default
(config-ip-sla-jitter)# request-data-size <bytes>

; 5000 ms default
(config-ip-sla-jitter)# threshold <ms>
(config)# ip sla responder

; 3600s default
(config)# ip sla schedule <N> life <sec>

; authC control messages
(config)# ip sla key-chain <CHAIN>
# show ip sla configuration
# show ip sla statistics

Track

  • metric multiplier: divide IGP metric to get track metric
    • OSPF, RIP: 1
    • static, IS-IS: 10
    • BGP, EIGRP: 2560
  • if threshold is reached (e.g., metric tracking for route) – trigger action
(config)# track resolution ip|ipv6 route <IGP> <RESOLUTION>

(config)# track <N> ip sla <SLA> [state|reachability]

; against flapping
(config-track)# delay down <sec> up <sec>

(config)# track <N> ip route <PREFIX> metric threshold

; defaults: up = 254, down = 255, up < down
(config-track)# threshold metric up|down <M>
; SEQ – sequence number, N – track object
(config-route-map)# set ip next-hop verify-reachability <IP> <SEQ> track <N>
# show track