Raspberry Pi のIPアドレスを固定にする方法です。
検証した環境
$ cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"
NAME="Debian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"
VERSION_CODENAME=bullseye
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
$ uname -r
5.15.56-v8+動的IPアドレス
おそらく、動的にIPアドレスが、DHCPサーバ（ルータ）から割り振られていると思います。
$ ifconfig
eth0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
ether dc:a6:32:92:d2:32 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 18 bytes 2147 (2.0 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 18 bytes 2147 (2.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.29 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::5ca4:1c91:67a6:2216 prefixlen 64 scopeid 0x20<link>
ether dc:a6:32:92:d2:33 txqueuelen 1000 (Ethernet)
RX packets 220 bytes 17810 (17.3 KiB)
RX errors 0 dropped 1 overruns 0 frame 0
TX packets 174 bytes 27147 (26.5 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0設定ファイルの編集
$
sudo cp -a /etc/dhcpcd.conf /etc/BK-dhcpcd.conf.original
$ sudo vi /etc/dhcpcd.conf
44,45c44,45
< #interface eth0
< #static ip_address=192.168.0.10/24
---
> interface wlan0
> static ip_address=192.168.1.71/24
47,48c47,48
< #static routers=192.168.0.1
< #static domain_name_servers=192.168.0.1 8.8.8.8 fd51:42f8:caae:d92e::1
---
> static routers=192.168.1.1
> static domain_name_servers=192.168.1.1マシンリブート
$ sudo systemctl reboot静的IPアドレスの確認
設定したIPアドレスになっていると思います。
$ ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536
qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500
qdisc mq state DOWN group default qlen 1000
link/ether dc:a6:32:92:d2:32 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
qdisc pfifo_fast state UP group default qlen 1000
link/ether dc:a6:32:92:d2:33 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.71/24 brd 192.168.1.255 scope global noprefixroute wlan0
valid_lft forever preferred_lft forever
inet6 fe80::5ca4:1c91:67a6:2216/64 scope link
valid_lft forever preferred_lft forever