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Old 09-29-2013, 03:53 AM   #1
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Strange problem with IPv6 Neighbor Solicitation

I've observed a strange problem with IPv6 Neighbor Discovery while installing a new Linux server based on Fedora 19, Kernel 3.11.1.
After awhile it simply stops sending out Neighbor Discovery packages, and all Neighbors change status to 'FAILED'.

The server I was installing was handling rather a lot of VLAN's, so to make sure, I set up 2 separate computers, directly connected LAN-2-LAN via a dum, unmanaged switch. Installed F19, X64 – minimal netinst on both.

One is set up as a router, with RADVD installed, and the other as a normal client.

Server #1 was given an IPv6 address: 2a02:2190:1004::1/64 and RADVD was given that subnet and enabled.
Server #2 was nicely assigned a IPv6 address from RADVD: 2a02:2190:1004:0:a00:27ff:fe66:3033/64 and both could now ping each others IPv6 address with no problem, and both kept their Neighbor tables updated.

Then I do ”systemctl restart network” on Server #1 an immediately Server #2 stop receiving ping-reply's.

Tcpdump shows that Server #2 keeps sending ICMPv6 Echo-request packages, but receives no answers, and “ip -6 n sh” on Server #1 shows that Server #2's Neighbor entry now is marked as 'FAILED'

[root@router1 ~]# ip -6 n sh
fe80::a00:27ff:fe66:3033 dev p7p1 lladdr 08:00:27:66:30:33 STALE
fe80::a00:27ff:fe0f:506c dev p7p1 lladdr 08:00:27:0f:50:6c router STALE
2a02:2190:1004:0:a00:27ff:fe66:3033 dev p7p1 FAILED

After a short while, Server #2 sends out a neighbor solicitation and Server #1 answers:

20:47:23.400324 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 32) 2a02:2190:1004:0:a00:27ff:fe66:3033 > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a02:2190:1004::1 source link-address option (1), length 8 (1): 08:00:27:66:30:33

20:47:23.400413 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 32) 2a02:2190:1004::1 > 2a02:2190:1004:0:a00:27ff:fe66:3033: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2a02:2190:1004::1, Flags [solicited, override] destination link-address option (2), length 8 (1): 08:00:27:0f:50:6c

But Server #1 never sends out any neighbor solicitation and Server #2 remains 'FAILED' indefinitely and nothing I do changes that. Only a complete restart of Server #1 brings it back to working again.

I REALLY hope somebody out there can point out the error of my ways, 'cause this is driving me crazy
Old 10-01-2013, 02:45 PM   #2
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What's output, systemctl status? Any fail on log?
Old 09-13-2014, 08:43 AM   #3
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Registered: Sep 2014
Distribution: Debian Wheezy
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Based on the 2a02:2190 prefix I can tell that we have the same ISP.

I've been looking for instructions on how to set up IPv6 on this ISP's network. I've already been in contact with their technicians who told me that they have disabled neighbor discovery because of problems with the IPv6 implementation on Windows Vista clients.

Did you experience any difficulties setting up IPv6 on your Internet connection? My IPv4 Internet connection works perfectly, but I've been unable to get IPv6 to work (I've been trying for days). Wireshark shows plenty of inbound IPv4 traffic, but no IPv6 whatsoever. I am unable to even ping the gateway they've given me.

Would you mind sharing your IPv6 configuration? You're very welcome to contact me via email if you prefer.

På forhånd tak


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