Verify Latency when You Ping 'From' or 'To' Nexus Switch

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Updated:September 18, 2024
Document ID:222402

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    Introduction

    This document describes the latency expectations of a ping or traceroute 'To' or 'From' a Nexus switch IP.  A delayed response from the switch is an expected behavior. 

    Problem

    Latency is observed when we ping from or to switch IP on Nexus switch.

    Nexus-1# ping6 fc00::2
    64 bytes from fc00::2: icmp_seq=47 time=12.067 ms
    64 bytes from fc00::2: icmp_seq=48 time=12.452 ms
    64 bytes from fc00::2: icmp_seq=49 time=12.575 ms
    64 bytes from fc00::2: icmp_seq=50 time=12.903 ms
    64 bytes from fc00::2: icmp_seq=51 time=14.532 ms
    64 bytes from fc00::2: icmp_seq=52 time=15.029 ms
    64 bytes from fc00::2: icmp_seq=53 time=15.188 ms
    64 bytes from fc00::2: icmp_seq=54 time=15.447 ms
    64 bytes from fc00::2: icmp_seq=55 time=15.788 ms
    64 bytes from fc00::2: icmp_seq=56 time=16.136 ms
    64 bytes from fc00::2: icmp_seq=57 time=16.29 ms

    ----------------------------------------------------------------------------

    Nexus-1# ping 10.1.1.1
    64 bytes from 10.1.1.1: icmp_seq=21 ttl=254 time=17.397 ms
    64 bytes from 10.1.1.1: icmp_seq=22 ttl=254 time=17.977 ms
    64 bytes from 10.1.1.1: icmp_seq=23 ttl=254 time=18.668 ms
    64 bytes from 10.1.1.1: icmp_seq=24 ttl=254 time=19.613 ms
    64 bytes from 10.1.1.1: icmp_seq=25 ttl=254 time=20.018 ms
    64 bytes from 10.1.1.1: icmp_seq=26 ttl=254 time=20.539 ms
    64 bytes from 10.1.1.1: icmp_seq=27 ttl=254 time=20.647 ms
    64 bytes from 10.1.1.1: icmp_seq=28 ttl=254 time=21.02 ms
    64 bytes from 10.1.1.1: icmp_seq=29 ttl=254 time=21.504 ms
    64 bytes from 10.1.1.1: icmp_seq=30 ttl=254 time=21.622 ms 

    Solution

    We recommend to check the latency by doing ping test between end devices/hosts, instead of doing a ping test to switch IP.

    • When ICMP request is received to the switch, it is processed by the switch CPU/Supervisor.
    • ICMP packets are low priority or non-critical traffic to the switch.
    • Switch CPU/Supervisor need to process other critical traffic such as STP BPDU’s, UDLD, BFD, LACP, OSFP, BGP and other control plane traffic on priority.
    • So when we ping the switch IP there can be latency.

    Verification

    • Using ethanalyzer command we can check if there are any unusual ICMP traffic received on the switch.
    •  In below output we could see ICMP requests received from multiple hosts/sources to switch IP.
    NEXUS# show ip interface brief
    IP Interface Status for VRF "default"(1)

    Interface            IP Address      Interface Status
    Vlan10               10.1.1.1        protocol-up/link-up/admin-up

    NEXUS# ethanalyzer local interface inband display-filter icmp limit-c 0

    Capturing on 'ps-inb'

        1 2024-05-13 13:05:49.296574516    10.1.1.35 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        2 2024-05-13 13:05:49.298725978    10.1.1.51 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        3 2024-05-13 13:05:49.299935463    10.1.1.60 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        4 2024-05-13 13:05:49.303159980    10.1.1.84 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        5 2024-05-13 13:05:49.305450067   10.1.1.101 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        6 2024-05-13 13:05:49.307596053    10.1.1.17 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        7 2024-05-13 13:05:49.309881152    10.1.1.34 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        8 2024-05-13 13:05:49.313239980    10.1.1.59 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
        9 2024-05-13 13:05:49.315391183    10.1.1.75 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       10 2024-05-13 13:05:49.317675859    10.1.1.92 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       11 2024-05-13 13:05:49.319960319   10.1.1.109 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       12 2024-05-13 13:05:49.323185627    10.1.1.33 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       13 2024-05-13 13:05:49.325471951    10.1.1.50 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       14 2024-05-13 13:05:49.327622826    10.1.1.66 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       15 2024-05-13 13:05:49.329906456    10.1.1.83 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       16 2024-05-13 13:05:49.332057200    10.1.1.99 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       17 2024-05-13 13:05:49.334341820    10.1.1.16 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64
       18 2024-05-13 13:05:49.336626919    10.1.1.33 → 10.1.1.1     ICMP 60 Echo (ping) request  id=0x0000, seq=0/0, ttl=64

    Revision History

    Revision Publish Date Comments
    1.0
    18-Sep-2024
    Initial Release
    TAC Authored

    Contributed by Cisco Engineers

    • Kiran M
      TAC
    • Srinivasa Reddy
      TAC

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