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I'm having a very strange problem with IPv6 pings on OpenWRT (fon-ng firmware with IPv6 enabled) and hoping someone can help with investigation.

In short - wpan0 interface with address aaaa::1/64 is created. ping6 to a host behind this interface (aaaa::250:c2a8:c3d4:a645) fails. But tcpdump shows ICMP6 requests and replies OK. curl to the host web page also times out.

ping6 to aaaa::1 is OK.

Any hint where the problem could be? Command lines and selected logs are below.

tunslip6 command line:
usr/bin/tunslip6 -B 9600 -s /dev/ttyUSB1 -t wpan0 aaaa::1/64

Interface is created and TX/RX packages (ifconfig output):

wpan0     Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
        inet6 addr: fe80::1/64 Scope:Link
        inet6 addr: aaaa::1/64 Scope:Global
        UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
        RX packets:62 errors:0 dropped:0 overruns:0 frame:0
        TX packets:62 errors:0 dropped:0 overruns:0 carrier:0
        collisions:0 txqueuelen:500
        RX bytes:6448 (6.2 KiB)  TX bytes:6448 (6.2 KiB)

ping6 fails:

root@Fonera:~# ping6 aaaa::250:c2a8:c3d4:a645
PING aaaa::250:c2a8:c3d4:a645 (aaaa::250:c2a8:c3d4:a645): 56 data bytes

--- aaaa::250:c2a8:c3d4:a645 ping statistics ---
12 packets transmitted, 0 packets received, 100% packet loss

Traffic on the interface is OK (tcpdump -i wpan0 output):

11:25:22.876799 IP6 aaaa::1 > aaaa::250:c2a8:c3d4:a645: ICMP6, echo request, seq 0, length 64
11:25:23.106712 IP6 aaaa::250:c2a8:c3d4:a645 > aaaa::1: ICMP6, echo reply, seq 0, length 64
11:25:23.880472 IP6 aaaa::1 > aaaa::250:c2a8:c3d4:a645: ICMP6, echo request, seq 1, length 64
11:25:24.113802 IP6 aaaa::250:c2a8:c3d4:a645 > aaaa::1: ICMP6, echo reply, seq 1, length 64
11:25:24.890394 IP6 aaaa::1 > aaaa::250:c2a8:c3d4:a645: ICMP6, echo request, seq 2, length 64
11:25:25.120966 IP6 aaaa::250:c2a8:c3d4:a645 > aaaa::1: ICMP6, echo reply, seq 2, length 64
11:25:25.900357 IP6 aaaa::1 > aaaa::250:c2a8:c3d4:a645: ICMP6, echo request, seq 3, length 64

Routing table is:

root@Fonera:~# ip -6 route
aaaa::/64 dev wpan0  metric 256  expires -67sec mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev eth0  metric 256  expires -2924sec mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev eth0.1  metric 256  expires -2922sec mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev ra0  metric 256  expires -2919sec mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev br-lan  metric 256  expires -2917sec mtu 1500 advmss 1440 hoplimit 4294967295
fe80::/64 dev wpan0  metric 256  expires -66sec mtu 1500 advmss 1440 hoplimit 4294967295

Firewall is disabled:

root@Fonera:~# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
root@Fonera:~# ip6tables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
root@Fonera:~# ping6 aaaa:0000:0000:0000:0250:c2a8:c3d4:a645
PING aaaa:0000:0000:0000:0250:c2a8:c3d4:a645 (aaaa::250:c2a8:c3d4:a645): 56 data bytes

--- aaaa:0000:0000:0000:0250:c2a8:c3d4:a645 ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss
Maxim Osipov
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  • Can you please paste the routing table of the target machine too? (ip -6 route), btw, global addresses shoudl start with a 2 or a 3, so it's possible there is a 2000::/3 set for 'default route' – mulaz May 16 '12 at 15:20
  • Thank you! Routing table shows only link local addresses, so there must be something else, I think. – Maxim Osipov May 16 '12 at 17:14
  • Maybe a firewall problem? Can you ping the link local addresses of other hosts? – AndreasM May 16 '12 at 18:35
  • And doesn't look like a firewall - at least iptables are clean and nice... Common, any ideas how to debug it further!? :) – Maxim Osipov May 16 '12 at 19:44
  • You did check with `ip6tables`, did you? – AndreasM May 17 '12 at 20:19
  • Yes, I did (at is up there just below iptables output). Anyway, the problem was fixed by changing router firmware to bleeding edge OpenWRT. Thank you! – Maxim Osipov May 18 '12 at 22:47

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