A CNAME, or Alias, DNS record has 3 fundamental parts:
- the left-hand-side, a.k.a. the alias or label, a.k.a. the value that's looked up
- the right-hand-side, a.k.a. the CNAME, a.k.a. the result of a lookup
- the time-to-live, a.k.a. TTL
Here are some examples:
www.example.com 7200 IN CNAME someothername.example.com
pages.example.com 86400 IN CNAME app-9123.example.info
pages.example.net 86400 IN CNAME app-9123.example.info
The IN CNAME part is going to be the same for all CNAME records (and may not even be shown in a given DNS host's UI).
The TTL is in seconds and determines how long the right-hand-side (CNAME result) will be cached. During that period, if a server already has a result, the lookup will not run again; the previous result will be reused. You can start with a low TTL value while you're making sure things work. Then work toward at least a day (86400).
The left-hand-side is the Alias: that's your Marketo LP domain.
The right-hand-side is the CNAME: that's the canonical name, meaning the "real name" of your LP domain. This is your Account String, followed by .mktoweb.com. You get your Account String from the Marketo UI, under Admin » Integration » Landing Pages » Settings. If your Account String is blahzay then the CNAME is blahzay.mktoweb.com,
