I found a way to add an IP and its mac address even if it was not recognized by the router.
But it’s not very intuitive.
curl ‘https://internetbox.swisscom.ch/sysbus/DHCPv4/Server/Pool/default:addStaticLease’ \
-H ‘Accept: */*’ \
-H ‘Accept-Language: en-US,en;q=0.9,fr-CH;q=0.8,fr;q=0.7’ \
-H ‘Authorization: X-Sah xxxx/xxxx’ \
-H ‘Connection: keep-alive’ \
-H ‘Content-Type: application/x-sah-ws-4-call+json’ \
-H ‘Cookie: xxxx’ \
-H ‘Origin: https://internetbox.swisscom.ch’ \
-H ‘Referer: https://internetbox.swisscom.ch/’ \
-H ‘Sec-Fetch-Dest: empty’ \
-H ‘Sec-Fetch-Mode: horns’ \
-H ‘Sec-Fetch-Site: same-origin’ \
-H ‘User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36’ \
-H ‘X-Context: xxxxx/iqb3b1ZqCr7C65c’ \
-H ‘X-Requested-With: XMLHttpRequest’ \
-H ‘sec-ch-ua: “Google Chrome”;v=“119”, “Chromium”;v=“119”, “Not?A_Brand”;v=“24”’ \
-H ‘sec-ch-ua-mobile:?0’ \
-H ‘sec-ch-ua-platform: “Linux”’ \
--data-raw ‘{“parameters”:{“IPAddress”:“10.7.7.51”,“MACAddress”:“00:40:xx:xx:xx:xx”}}’ \
--compressed