IPV6 forwards FritzBox (DS-LITE) <-> OpenWrt <-> LAN machine

Installing and Using OpenWrt Network and Wireless Configuration
21

Thanks @mpa for this information.
So I did the tcpdump, pinged google and captured packages on the fritzbox:

dump
dump1079×1812 126 KB

(there is 17 different connection for which I can capture the packages, and I am not quite sure which ones to use, so I dumped multiple ones.)

The result are .eth dumps, which all are a couple of MB big after a couple of seconds.
I then open them in wireshark and try to find the the packages belonging to my ping.
I guess, good filter options would be google's ipv6 or the associated "flowlabel".

The problem is, I have never used wireshark before and am rather overwhelmed. Also I don't feel like posting entire dumps online.

However, after some manual searching, I think I found the corresponding package in the dump of the "LAN" connection:

wireshark-packet
wireshark-packet1207×1368 227 KB

If anyone has a hint how to do so with wireshark, it might help, even though I think I will figure it out eventually :wink:

Will come back as soon as I have more information.

22

ipv6.addr == 2001:abcd:ef01::1 <- the lan host address here.

23

I only find records of the hosts address in the "lan" packet dump, and they all look like the second screenshot I posted.

The first four under "internet" don't show packages originating from the host.
All of the ones under "Netzwerkschnittstellen" that I have tried (besides LAN) are empty.

I haven't looked at all possible dumps. Any idea where to look explicitly?

Or how to proceed with the package captured from LAN?

24

On a side note:
ping ipv6.google.com from the OpenWRT itself works fine...

25

Since you can capture the ping from the OpenWrt, you should know which are the lan and wan interfaces of the Fritz.

These are echo requests, the replies are missing.

This can be bad. The Fritz might be dropping the packets.
Also have a look here.

26

To narrow down the large amount of packets, enter this filter expression:

icmp or icmpv6

It is also possible to build a more specific filter from a packet's properties:
In the “Packet Details” Pane, right-click on a field, for example:

Type: Echo (ping) reply (129)

and choose one of the filtering options from the pop-up menu.

Documentation about Display Filters:

https://www.wireshark.org/docs/wsug_html_chunked/ChWorkBuildDisplayFilterSection.html

1 Like
27

Dear all,

thanks to everyone who tried to help me out here. Since I could not figure it out, I decided to change ISP to a company that gives me a public ipv4. So my problems are solved now by other means.

Sorry I could not report anything better and thanks again.

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