The task: find and print lines from a file that contain any (IPv4) IP address except those on the local LAN (local LAN uses class C addresses of the 192.168.1.x variety). I (having cribbed bits from various online searches) use sed and a couple of pipes to do this fairly effectively, as follows:

sed -rn '/([0-9]{1,3}\.){3}[0-9]{1,3}/p' logfile.txt | sed '/192\.168\.[[:digit:]]\.[[:digit:]]\{,3\}/d' 

Question: are there other or better ways of doing this using alternate utilities, or perhaps improvements I could make to the incantation I've come up with?

Background: the purpose is, on a non-systemd (Void Linux) system, to trawl daily a system log file that contains ssh connection information to see who, other than hosts on my local LAN, has been trying to make ssh connections/queries. The file containing the target information is generated daily using svlogtail, after which the above command runs. The system then e-mails me the output.

Sample input data:

2020-06-21T08:28:04.56472 auth.err: sshd[21813]: error: Bind to port 22 on 192.168.2.16 failed: Cannot assign requested address. 2020-06-23T11:12:59.04698 auth.info: Jun 23 06:12:59 sshd[25036]: banner exchange: Connection from 194.61.24.4 port 1565: invalid format 2020-07-14T14:53:30.54107 auth.info: Jul 14 09:53:30 sshd[30149]: banner exchange: Connection from 31.207.47.114 port 1848: invalid format 2020-09-06T15:25:19.32385 auth.info: Sep 6 10:25:19 sshd[18826]: banner exchange: Connection from 193.142.146.216 port 30884: invalid format 2021-02-05T12:24:30.42762 auth.info: Feb 5 06:24:30 sshd[27489]: banner exchange: Connection from 94.232.47.170 port 107: invalid format 2021-02-19T15:48:10.29592 auth.info: Feb 19 09:48:10 sshd[2924]: Disconnected from user 192.168.1.10 port 33732 

Desired output (this acceptable output is what I get after running above sed commands)

2020-06-23T11:12:59.04698 auth.info: Jun 23 06:12:59 sshd[25036]: banner exchange: Connection from 194.61.24.4 port 1565: invalid format 2020-07-14T14:53:30.54107 auth.info: Jul 14 09:53:30 sshd[30149]: banner exchange: Connection from 31.207.47.114 port 1848: invalid format 2020-09-06T15:25:19.32385 auth.info: Sep 6 10:25:19 sshd[18826]: banner exchange: Connection from 193.142.146.216 port 30884: invalid format 2021-02-05T12:24:30.42762 auth.info: Feb 5 06:24:30 sshd[27489]: banner exchange: Connection from 94.232.47.170 port 107: invalid format