Inleiding
Dit document beschrijft de latentieverwachtingen van een ping of traceroute 'To' of 'From' een Nexus switch IP. Een vertraagde reactie van de switch is een verwacht gedrag.
Probleem
Latentie wordt waargenomen wanneer we van of naar switch IP op Nexus switch pingen.
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
Oplossing
Wij adviseren om de latentie te controleren door pingtest tussen eindapparaten/hosts te doen, in plaats van het doen van een pingtest aan switch IP.
- Wanneer ICMP-verzoek aan de switch wordt ontvangen, wordt dit verwerkt door de switch CPU/supervisor.
- ICMP-pakketten zijn weinig prioritair of niet-kritisch verkeer naar de switch.
- Switch CPU/supervisor moet ander kritisch verkeer zoals STP BPDU's, UDLD, BFD, LACP, OSFP, BGP en ander besturingsplane op prioriteitsverkeer verwerken.
- Dus als we de switch IP pingen kan er latentie zijn.
Verificatie
- Met behulp van ethanalyzer commando kunnen we controleren of er ongebruikelijk ICMP verkeer ontvangen op de switch.
- In onderstaande output konden we ICMP verzoeken ontvangen van meerdere hosts/bronnen om IP switches.
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