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ping6 - Time exceeded: Hop limit

Shadow Hawkins on Tuesday, 14 February 2017 16:35:39

I am trying to set up my new Raspberry Pi up as my IPv6 gateway, using aiccu, but when I try a test connection via: telnet ipv6.google.com 443 I get a timeout. I then try a ping6 to the same address, but get:

$ ping6 ipv6.google.com
PING ipv6.google.com(yyz08s10-in-x0e.1e100.net) 56 data bytes
From yyz08s10-in-x0e.1e100.net icmp_seq=1 Time exceeded: Hop limit
From yyz08s10-in-x0e.1e100.net icmp_seq=2 Time exceeded: Hop limit
^C
--- ipv6.google.com ping statistics ---
2 packets transmitted, 0 received, +2 errors, 100% packet loss, time 1001ms

I am not sure whether the issue is at my end or at the PoP side. What should I be examining? The settings in my /etc/aiccu.conf (masking sensitive info):

username XXXXX
password XXXXX
protocol tic
ipv6_interface sixxs
tunnel_id XXXXX
verbose false
daemonize true
automatic true
requiretls false
behindnat true

When I set daemonize false and verbose true, I see no errors in the startup sequence. My PoP is uschi02.

ping6 - Time exceeded: Hop limit

Jeroen Massar SixXS Staff

on Tuesday, 14 February 2017 16:47:13

I get a timeout. I then try a ping6 to the same address, but get:

Instead of ping, try traceroute, it will tell you what route is being taken for those packets. Do note that Google is a bad network to test connectivity towards as they use all kinds of tricks to make their performance the way it is (amongst others ignored ICMPv6 Packet Too Big, as their load balancers do not support it, and thus they guess TCP MSS instead, yes, UDP is SoL), thus misdiagnosis as one does not see their end is very possible.

The settings in my /etc/aiccu.conf (masking sensitive info):

AICCU configuration has very little to do: when the system is misconfigured before AICCU runs, it can't magically fix it. And of course, it can't fix any routing issues either. Hence, why there is a "Problems Checklist" on the contact page which is what the big yellow/orange boxes when posting point too.

ping6 - Time exceeded: Hop limit

Shadow Hawkins on Wednesday, 15 February 2017 04:51:23

The Raspberry Pi is a model 3 and both eth0 and wlan0 are connected to the local network. Output of uname: Linux balsa 4.4.34-v7+ #930 SMP Wed Nov 23 15:20:41 GMT 2016 armv7l GNU/Linux Playing around indicates the issue only happens if wlan0 is up. When both interfaces are up:

eth0      Link encap:Ethernet  HWaddr b8:27:eb:40:7e:e5  
          inet addr:192.168.2.28  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: 2001:4978:15d:feed::1/64 Scope:Global
          inet6 addr: fe80::57d6:1d7:8c17:6b2b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:65719 errors:0 dropped:1 overruns:0 frame:0
          TX packets:46200 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:50720760 (48.3 MiB)  TX bytes:45893098 (43.7 MiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:204 errors:0 dropped:0 overruns:0 frame:0
          TX packets:204 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:17264 (16.8 KiB)  TX bytes:17264 (16.8 KiB)

sit0      Link encap:IPv6-in-IPv4  
          NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

sixxs     Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet6 addr: fe80::4878:f:48:2/64 Scope:Link
          inet6 addr: 2001:4978:f:48::2/64 Scope:Global
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1280  Metric:1
          RX packets:34810 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10494 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:42924095 (40.9 MiB)  TX bytes:999427 (976.0 KiB)

wlan0     Link encap:Ethernet  HWaddr b8:27:eb:15:2b:b0  
          inet addr:192.168.2.29  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::e659:fc06:d4cd:230a/64 Scope:Link
          inet6 addr: 2001:4978:15d:feed:d3b9:b0d3:9598:655/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:631 errors:0 dropped:313 overruns:0 frame:0
          TX packets:18082 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:128977 (125.9 KiB)  TX bytes:4659397 (4.4 MiB)

/etc/network/interfaces:

source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

iface eth0 inet manual

iface eth0 inet6 static
   pre-up modprobe ipv6
   address 2001:4978:15d:feed::1
   netmask 64

allow-hotplug wlan0
iface wlan0 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1
iface wlan1 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

# IPv6
iface wlan0 inet6 static
#   pre-up modprobe ipv6
#   address 2001:4978:15d:feed::1
#   netmask 64

While only impacting radvd and not the base connectivity I also noticed that 2001:4978:15d:feed::1 wasn't being assigned and instead I needed to do this manually: sudo /sbin/ip -6 addr add 2001:4978:15d:feed::1/64 dev eth0

ping6 - Time exceeded: Hop limit

Jeroen Massar SixXS Staff

on Wednesday, 15 February 2017 06:42:13

Playing around indicates the issue only happens if wlan0 is up.

Check 'ip -6 ro show' likely you see that your Wireless is bridged to your Ethernet. Hence, eth0 on your device, announces connectivity to wlan0 through your Access Point which bridges Ethernet and Wireless. Thus, bringing up eth0 and wlan0 at the same time is a bad idea in this configuration unless you apply a lot of extra configuration.

While only impacting radvd and not the base connectivity I also noticed that 2001:4978:15d:feed::1 wasn't being assigned and instead I needed to do this manually:

sudo /sbin/ip -6 addr add 2001:4978:15d:feed::1/64 dev eth0

That is because forwarding is enabled on the interface, you should put that in /etc/network/interfaces. Also, you might be missing a 'auto eth0' line there. Instead of 'pre-up modprobe ipv6' stuff that in /etc/modules and it will load way before your networking comes up. That might resolve it too. Running a Debian based image will resolve all that, as they got IPv6 built in per default for a long long time already.

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