Der Hund des Nachbarn bellt viel - why is Nachbarn not Nachbarnes?

I've just been looking at the genitive case and read the rules about endings - el, er, en or ending in a vowel taking an s ending while vowels ending in a consonant take es.

So I'm a bit confused at why in the following statement why the word Nachbarn does not have an es ending as it is masculine :

Der Hund des Nachbarn bellt viel

As Nachbarn is the plural should it not become : Der Hund der Nachbarn bellt viel?

Any help would be great!

Thanks

Craig

I asked a somewhat similar question about a different sentence, maybe the explanation will help?
https://members.rocketlanguages.com/members/forum/german-grammar/der-bruder-einesdes-neuen-nachbarn-arbeitet-bei-mercedes-benz

It does seem a little odd to introduce such a tricky point without explanation.

Thanks for that. I'm not sure the explanation from Lucia really clears that up, top be honest.

Yes, I find Lucia's explanations a bit cryptic too. :-)
If I understand correctly, Nachbar is a weak noun which means it takes an "n" in genitive singular so Nachbarn is singular, thus des Nachbarn.

I found this link with more than you want to know about weak nouns!
https://www.duolingo.com/comment/10973844/German-s-Weak-Nouns-Explanation

 

Yes, that seems to make sense.

Thanks for that link, too.  Although there's a lot going on as far as weak nouns go, it does clear up my questions about Nachbarn. 

Thanks again!