Cisco N9K 9364C GX – IPSLA & HSRP

panFeb 11, 2025

Background: The idea scenario is HSRP configured under SVI interface which runs over the vPC port-channel.

1. IP SLA

1.1 Configuration

feature sla sender

ip sla 1
  icmp-echo 172.16.0.2 source-interface Ethernet1/1
    threshold 100
    timeout 500
    frequency 1

ip sla schedule 1 life forever start-time now

This IPSLA sends 1 echo message every 1 second. If it doesn’t receive the reply within 500 milliseconds, it counts as a failure. Threshold sets the RTT threshold to 100 milliseconds.

The durability should be frequency > timeout > threshold .

1.2 Show Output

Nexus-9364C-GX# show ip sla statistics 

IPSLAs Latest Operation Statistics

IPSLA operation id: 1
        Latest RTT: 1 milliseconds
Latest operation start time: 10:48:51.689 UTC Tue Feb 11 2025
Latest operation return code: OK
Number of successes: 19
Number of failures: 0
Operation time to live: forever

Nexus-9364C-GX-1# show ip sla configuration 
IP SLAs Infrastructure Engine-III
Entry number: 1
Owner: 
Tag: 
Operation timeout (milliseconds): 500
Type of operation to perform: icmp-echo
Target address/Source interface: 172.16.0.2/Ethernet1/1
Traffic-Class parameter: 0x0
Type Of Service parameter: 0x0
Target hostname/Source hostname : NA/NA
Switch ID: 0
Profile ID: 0
Interface: 
Request size (ARR data portion): 28
Verify data: No
Vrf Name: default
Schedule:
   Operation frequency (seconds): 1  (not considered if randomly scheduled)
   Next Scheduled Start Time: Start Time already passed
   Group Scheduled : FALSE
   Randomly Scheduled : FALSE
   Life (seconds): Forever
   Entry Ageout (seconds): never
   Recurring (Starting Everyday): FALSE
   Status of entry (SNMP RowStatus): Active
Threshold (milliseconds): 100
Distribution Statistics:
   Number of statistic hours kept: 2
   Number of statistic distribution buckets kept: 1
   Statistic distribution interval (milliseconds): 20
History Statistics:
   Number of history Lives kept: 0
   Number of history Buckets kept: 15
   History Filter Type: None

Nexus-9364C-GX-1# show ip sla application 

        IP Service Level Agreements
Version: Round Trip Time MIB 2.2.0, Infrastructure Engine-III

Supported Operation Types:
        icmpEcho, udpEcho, tcpConnect, http, dns, udpJitter, ctp

Supported Features:
        
IP SLAs low memory water mark: 1770526486
Estimated system max number of entries: 248196

Estimated number of configurable operations: 92030
Number of Entries configured  : 1
Number of active Entries      : 1
Number of pending Entries     : 0
Number of inactive Entries    : 0
Time of last change in whole IP SLAs: 10:48:33 UTC Tue Feb 11 2025

2. Track in HSRP

2.1 Configure Track

track 1 ip sla 1 reachability

Nexus-9364C-GX# show track 1
Track 1
  IP SLA 1 Reachability
  Reachability is UP
  1 changes, last change 00:01:18
  Latest operation return code: OK
  Latest RTT (millisecs): 1

2.2 Use Track in HSRP

Use Track under HSRP. The priority is decreased by 10 by default.

interface Vlan10
  no shutdown
  no ip redirects
  ip address 10.0.0.2/24
  no ipv6 redirects
  ip router eigrp 20
  ip passive-interface eigrp 20
  ip arp timeout 450
  hsrp version 2
  hsrp 10 
    preempt delay minimum 30 reload 120 
    priority 105
    timers msec 250 msec 750
    ip 10.0.0.1
    track 1 
    # track 1 decrement 20

2.3 Show Output

Once the tracked interface is down, the SVI interface HSRP priority is decreased by 10.

Nexus-9364C-GX# show hsrp 
Vlan10 – Group 10 (HSRP-V2) (IPv4)
  Local state is Initial(Interface Down), priority 95 (Cfged 105), may preempt
    Forwarding threshold(for vPC), lower: 0 upper: 105 
  Preemption Delay (Seconds) Reload:120 Minimum:30 
  Hellotime 250 msec, holdtime 750 msec
  Virtual IP address is 10.0.0.1 (Cfged)
  Active router is unknown
  Standby router is unknown 
  Authentication text “cisco”
  Virtual mac address is 0000.0c9f.f00a (Default MAC)
  0 state changes, last state change never
    Track object 1 state DOWN decrement 10
  IP redundancy name is hsrp-Vlan10-10 (default)

When the reachability is restored, it will wait for 30 seconds until it returns to the configured priority and take back the active role.

Nexus-9364C-GX# show hsrp 
Vlan10 – Group 10 (HSRP-V2) (IPv4)
  Local state is Initial(Interface Down), priority 95 (Cfged 105), may preempt
    Forwarding threshold(for vPC), lower: 0 upper: 105 
  Preemption Delay (Seconds) Reload:120 Minimum:30 
  Hellotime 250 msec, holdtime 750 msec
  Virtual IP address is 10.0.0.1 (Cfged)
  Active router is unknown
  Standby router is unknown 
  Authentication text “cisco”
  Virtual mac address is 0000.0c9f.f00a (Default MAC)
  0 state changes, last state change never
    Track object 1 state DOWN decrement 10
  IP redundancy name is hsrp-Vlan10-10 (default)