Chapter 29. Troubleshooting

There are some pretty useful diagnostic tools on Arista switches, some of which we’ve already covered, such as tcpdump. Sometimes, we need to know more detail about what the switch is doing, and that’s where performance monitoring comes into play.


In Linux, you can follow live updates to a log file by using the tail -f filename command. You can do something similar when viewing your system log in EOS with the command-line interface (CLI) command show logging follow. Syslog messages are stored in Linux where any Linux person would expect to see them, namely, in /var/log/:

[admin@Arista ~]$ ls /var/log
EosInit           error.log              messages
NorCalInit        eventMon.db            nginx-access.log
Post              fneserver              nginx-error.log
agents            inotifyrun-local.log   ntpstats
btmp              inotifyrun-secure.log  ppp
cli               inotifyrun-sys.log     qt
cron              kernel.debug           secure
eos               lastlog                spooler
eos-console       libvirt                startup-config-output
eos-console-sync  logrot.log             tallylog
eos-monitor       maillog                wtmp
eos-monitor-sync  mcelog                 yum.log

/var/log/messages contains all of the syslog messages that you would see on the console. Note that you need sudo to view this file:

[admin@Arista ~]$ cd /var/log
[admin@Arista log]$ tail messages
tail: cannot open 'messages' for reading: Permission denied
[admin@Arista log]$ sudo tail messages Nov 29 02:07:34 Arista Stp: %SPANTREE-6-STABLE_CHANGE: Stp state is now stable Nov 29 02:07:56 Arista Cli: %SYS-5-CONFIG_I: Configured from console by admin on vty3 ( Nov 29 02:08:01 ...

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