How to redirect an entry's URL to a specific URL?
Instead of using a redirect, what about using the saved URLs directly with your links?

Let's say it's a channel with the handle myExternalLinks where you collect the links. The actual URL is entered into a field with the handle myLinkUrl.

This is the template code to list the links:

{% set links = craft.entries.section('myExternalLinks') %}

{% for link in links %}

    {#
     # Link to the URL entered into `myLinkUrl` instead of
     # linking to `entry.getUrl()` and then using a redirect on that entry template
     #}
    &lt;a href="{{ link.myLinkUrl }}"&gt;{{ link.title }}&lt;/a&gt;

{% endfor %}