Centos 6.7 Unable to ping local ipv6

Conz · 11-19-2015, 05:55 AM

I am trying to figure out ipv6 so as a start I am just trying to set up a local ipv6 lan with dhcp and a dns server (no gateways etc)
The machine I'm using is a Centos 6.7 machine that *used* to have ipv6 disabled.

I'm not entirely sure where the problem is as I have very little experience with ipv6. I *think* I have the subnetting correct in the dhcp, I picked an fd40 range as that is supposed to be the ipv6 local subnets.

I configured the dhcpd6 with:

Quote:

subnet6 fd40:9dc7:b528::/48 {
range6 fd40:9dc7:b528::1 fd40:9dc7:b528::FFFF;
# option dhcp6.name-servers fd40:9dc7:b528::1:1;
}

fd40:9dc7:b528::1:1 is the ip6 of my centos machine.

Quote:

eth0 Link encap:Ethernet HWaddr 00:50:56:83:35

F
inet addr:z.y.x.a Bcast:z.y.x.255 Mask:255.255.255.0
inet6 addr: fd40:9dc7:b528::1:1/64 Scope:Global
inet6 addr: fe80::250:56ff:fe83:35df/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:486474 errors:0 dropped:0 overruns:0 frame:0
TX packets:478646 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:45119824 (43.0 MiB) TX bytes:45596010 (43.4 MiB)

A client pc *does* get an ipv6 address from the server but I am unable to ping6 those ip's.
'ip neigh show' shows the ip6 ip's as STALE.
I cannot ping6 fd40:9dc7:b528::1:1 from the machine itself.

So now I'm slightly confused and any pointers would be appreciated :-)

Ser Olmy · 11-20-2015, 09:43 AM

Your DHCP setup looks correct, and you've selected a valid IPv6 address range.

When you say:

Quote:

Originally Posted by Conz

I cannot ping6 fd40:9dc7:b528::1:1 from the machine itself.

...do you mean the server is actually unable to ping its own IPv6 address? If so, you should check your ip6tables ruleset to make sure it's not blocking localhost traffic.

As long as the MAC addresses reported by ip -6 neigh show are correct, the fact that they're marked as STALE does not necessarily indicate a problem. Neighbor entries are supposed to have a very limited lifetime, and will be refreshed as soon as traffic starts flowing between the hosts in question. If an ip -6 neigh show command is run immediately after a ping6, it should show the entry as REACHABLE.

Conz · 11-20-2015, 11:54 AM

Quote:

Originally Posted by Ser Olmy

Your DHCP setup looks correct, and you've selected a valid IPv6 address range.

When you say:

...do you mean the server is actually unable to ping its own IPv6 address? If so, you should check your ip6tables ruleset to make sure it's not blocking localhost traffic.

Initially ip6tables was on and blocking dhcpd, that started working after I turned iptables off so it's not that blocking ping6.
And yes it's unable to ping fd40:9dc7:b528::1:1, so slightly confused here.