Angular 2 routerLinkActive always active for base path

This appears to be a known issue. A few workarounds are detailed in this thread: https://github.com/angular/angular/issues/8397

From Github Thread:

"you need to add an additional option to your routerLink."

[routerLinkActiveOptions]="{ exact: true }"

Then your home route will only be active if you're on the exact route. The home route with an empty path will be a partial match on all routes

As suggested by @TomRaine in this answer, you can add the property [routerLinkActiveOptions]="{ exact: true }" to your element:

<nav>
  <a [routerLink]="['/']" 
      [routerLinkActive]="['nav-active']"
      [routerLinkActiveOptions]="{ exact: true }">
    HOME
  </a>
  ...
</nav>