First of all, I added givemetheflag.com to the /etc/hosts file, as the description was saying.
I did a basic scan with nmap and I found 53 as open port, I searched and found out that usually port 53 is used for DNS servers:
Then, I got the flag with this with this command:
dig @10.10.26.77 givemetheflag.com and the flag was in the result
As always, I was curious and I tried
nslookup to see if I could get the flag using another command and I got it:
nslookup -type=A givemetheflag.com 10.10.26.77