How to open links on a website displayed in an iframe in another iframe?

I want to display websites in different iframes. This website is the web interface of a monitoring tool (Icinga). No problems so far.

If I press a button/link in one iframe (that contains e.g. the topology of the system monitored), the link to a deeper level (still Icinga web interface) shall open in another iframe.

If this is not possible, is there any other way to open links from a website in another window?

Thanks in advance for your help !

Christian

I am just learning html and have not found any solution on my research yet. Also, I have no clue of javascript so far. Using the target command just works for predefined links.