Need help with Map Tile URL Subdomains

Hi,

In the Map Tile URL Subdomains contain “abc” by default, and this creates three subdomains like a(.) URL, b(.) URL, c(.) URL. Everything is fine, but these three subdomains lookup dns for three times and it causes higher page load time.

I have tried with only “a” subdomain, which also working fine, and it creates single subdomain and lookup dns for once. Result in Page will load little faster.

My question is, Should I continue using Map Tile URL Subdomain as “a”? and Will it create any issue in future?

Thanks