Changed from VDSL to Kabel DSL: no more IPv4, and broken MTU


I just switched from VDSL with Vodafone to Kabel DSL in my Stuttgart home.

VDSL worked ok, with some cuts now and then, and some network congestions issues, but I had an IPv4, and no MTU problems when connecting to my work with VPN.


Now it seems that that the Kabel connection only gives me a ipv6 with MTU 1500, and the IPv4 has a lower MTU (and no correct packet segmentation). This is very problematic for me, as its killing most of my work VPN packets. In addition to that, I was using routing into ipv4 - i cannot do this now.


I had read online that I should be supposed to switch my modem to bridge mode, and get a ipv4 (and lose ipv6, which is fine), but it seems that the option is not available in the online meinkabel interface. Is this not possible in BW ? Something to do with Unitimedia ? (and honestly I did not even know I was subscribing to Unitymedia - my contract says vodafone everywhere)


Is there anything I can do ? I'm tempted to cancel the kabel connection and go back to VDSL

6 Antworten 6

Hello Chluz1,


you don't need to enable bridge mode to switch to dual stack. The requirements for switching to dual-stack are as follows:


HomeBox Option incl. Fritzbox 6660 4,99€/month or

Power Upload 2,99€/month (only bookable from 250 MBit/s) or

a Gigabit connection.


Do you already have one of these rates or options?


Many greetings,


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Hi, thank you for your answer.

We had indeeded subscribed to the PowerUpload function.

We made one phone call to the techincal service, and they were able to activate full dual stack for us, with bridging mode available.

I cannot emphasise how pleased I am to see that this is possible with Vodafone Kabel in BW !


We are now having issues with bandwidth, especially upload bandwidth, during workdays (its fine on the weekend). I have also noticed many occurances of packet loss on one of your peering partners, namely Liberty Global Infrastructure, with between 30 and 60% packet loss for host de-bfe18a-rt01-lag-1.aorta.net even on the weekend. I believe both problems to be separate issues.


I will monitor and document this back to the support team, but don't hesistate to comment if you have any ideas of how this could be resolved faster. We already have a ticket logged for the upload bandwidth issues, but have not heard or seen any progress for the last 10 days. 



Hey Chluz1,

Thank you for your feedback.


We will be happy to take a closer look at your problems with the bandwidth. Please send us a private message with the following data: Customer number, name, address, date of birth, state and current cell phone number.


Please let us know here as soon as the message is out.


Best regards



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If this is still relevant please provide a full traceroute and concrete examples where you don't see the full bandwidth. Keep in mind that ICMP is processed within the CPU of routers while forwarding happens with hardware acceleration on specialized ASICs and that the return path is distinct from your outbound path.


Hi all, the only remaining issue is still the bandwidth.


In fact, after improving in mid 2022, I'm afraid the situation has considerably worsened end of 2022 and early 2023. Upload speeds drop close to 4mbits per second at best, and at worst pings to google dns fail. This is mostly occuring in the evening.


Can we exchange over PM about this ?

Thanks in advance for your help.

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