No but port forwarding! Yes this will work with fritzbox.

VPN will work.

Please buy 7490 or 75xx.

I’ve tried forwarding ports 500, 1701, and 4500 for IPSec and IKE on UDP, but I still can not add 50 and 51 for ESP and AH. 

Why does O2 make this modem so limited? Is it the firewall blocking the protocols or the ports?

OpenVPN seems to work fine though.

Danke!

You got, what you pay for.

Unfortunately, I didn’t choose. It’s my landlord’s.

I’m trying to find a workaround without having to bother him to switch the box.

You don’t have to choose the HomeBox, it is just an option! In a year there are about 3 question about VPN so that’s nothing. And I don’t think O2 Wille change it. It is a HOME! box. 

And for 80% of the user it is ok.
Use a Fritzbox or any other professional router:

Cisco, Linksys, Lancom or bintec e.g.

That’s true. 

Does O2 allow connection from any modem? Or does it have specific connection protocols that only works with their OEM firmware?

You may use any modem that corresponds to the interface description. Please be aware that only one PPPoE session is allowed.

See also:

1TR112 Technical Specification of the U-Interfaces of xDSL Systems in the network of Deutsche Telekom

If you want to use telephone services:

Telefónica Schnittstellenbeschreibungen der Netzbetreiber nach FTEG §5

You could use any VDSL Router that is design for the german Telefon network.

You should not buy any Provider router, because most are for rent. And other are fixed to the provider network (like the o2 HomeBox).

Don’t buy any 7390 or 7350 from AVM they are out of date, they do not cause as much joy as the cheap price suggests. The AVM “way” is the easy way. There is not mutch that could be done wrong.

I personally prefer the be.ip plus from bintec. It can do more, but it also demands more from the user when it comes to configuration. But then you can also configure the banana in the room if necessary.

From AVM 7490 (a liitel old but for <= 100 Mbit OK). Or any 75X0 Router if you need 250 Mbit.

The Router should support VDSL / SVDSL or the spec @blablup send you.