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I am using a wifi repeater (AVM FRITZ!WLAN Repeater 310) to extend my wifi at home. I have noticed that when I am connected to the wifi of my main access point/dsl modem/router (Speedport W 724V) - let's call it wifi A - I can use ipv6 without any problems. When I am using the wifi of the repeater, wifi B, my computer gets ipv6 addresses, but I get no response when I am pinging my server on the internet for example. Also devices in wifi A cannot reach devices in wifi B via ipv6.

By using wireshark I discovered that neighbor solicitation messages to the solicited-node multicast address of devices in wifi B send from wifi A do not go through the repeater. These multicast addresses do work however if both devices are in wifi B.

Now my questions:

  • Does an ipv6 router need to use neighbor solicitation with the solicited-node multicast address when returning replies to ping requests or other tcp/udp packets?
  • Should the repeater forward such messages if a given multicast group exists in its wifi?
  • Are there other concepts in ipv6 I am forgetting which might cause my problems?

2 Answers 2

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Does an ipv6 router need to use neighbor solicitation with the solicited-node multicast address when returning replies to ping requests or other tcp/udp packets?

Normally – yes, but an IPv6-compatible access point might perform ND proxying to avoid unnecessarily waking up the client. (Many APs already do exactly this for IPv4 ARP.)

Additionally, if the AP does deliver the NS packet to the client, you might get different results if it supports "multicast-to-unicast" (which is more reliable, but sometimes confuses the receiving device) vs when it uses actual Wi-Fi multicast.

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This may seem sloppy, but you can force the iPv6 NDP entry on each end so they can communicate. (This is similar to manually adding a permanent ARP table entry so two IPv4 hosts can communicate when ARP fails.) This is how I get around the problem of no IPv6 connectivity when using wired<-->wirelss<-->wired bridging.

On Linux you would do this: "ip -6 neigh add (remote ipv6 address) lladdr (remote mac address) dev (interface)"

On Windows you would similarly use the "netsh interface ipv6 add neighbors (arguments)" command.

Ed Thubert has posted an IETF proposed solution to this issue here: https://tools.ietf.org/id/draft-thubert-6man-ipv6-over-wireless-00.html

Jeff

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