Add explanation of glue records in DNS (#1222)

content/roadmaps/100-frontend/content/100-internet/103-dns-and-how-it-works.md

@@ -5,3 +5,4 @@ The Domain Name System (DNS) is the phonebook of the Internet. Humans access inf
 <BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.cloudflare.com/en-gb/learning/dns/what-is-dns/'>What is DNS?</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=Wj0od2ag5sk'>DNS and How does it Work?</BadgeLink>
 <BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=7lxgpKh_fRY'>DNS Records</BadgeLink>
+<BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=e48AyJOA9W8'>When to add glue records to DNS settings</BadgeLink>