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#1 2020-01-05 23:53:33

freshscaped
Member
From: West Yorkshire
Registered: 2015-08-29
Posts: 60

Not picking up SLAAC allocated IPv6 address

Hi Folks,

Having been allocated an IPv6 address by SLAAC (from server host) and installing dhcpcd, started and enabled the latter I think correctly, couldn't ping out so decided to look at whether there is an ip6 address on the interface enp1s0.

What came out looks to me like it may be produced from two DUIDs with neither producing the allocated IPv6 address. How could this be and what can I do to correct matters?

~]# systemctl start dhcpcd@enp1s0.service
~]# systemctl enable dhcpcd@enp1s0.service 
Created symlink /etc/systemd/system/multi-user.target.wants/dhcpcd@enp1s0.service -> /usr/lib/systemd/system/dhcpcd@.service.

~]# ping -6 archlinux.org
PING archlinux.org(apollo.archlinux.org (2a01:4f8:172:1d86::1)) 56 data bytes
^C
--- archlinux.org ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5072ms


~]# ip -6 a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 2001:bc8:6005:127:81d3:52dc:d872:f854/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 2591997sec preferred_lft 604797sec
    inet6 2001:bc8:6005:127:99ea:ac0f:7162:10b5/64 scope global dynamic noprefixroute 
       valid_lft 2591997sec preferred_lft 604797sec
    inet6 fe80::cfdc:cf53:3945:166f/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

TIA,

Mike

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#2 2020-01-06 03:36:11

rsmarples
Member
Registered: 2009-05-12
Posts: 234

Re: Not picking up SLAAC allocated IPv6 address

You suggest the IP is allocated via DUID. This implies DHCPv6, but you have no /128 addresses which would only come from DHCPv6.
Both addresses look fine though and I assume you have a default route as 6 packets were transmitted.
Can you ping your IPv6 router?

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#3 2020-01-06 14:31:30

freshscaped
Member
From: West Yorkshire
Registered: 2015-08-29
Posts: 60

Re: Not picking up SLAAC allocated IPv6 address

Hi rsmarples and thank you for the response. I have to confess to being way out of my depth here. Having searched for how to find a router address without success I resorted to guessing.

In the response to

ip -6 route

the first line after the lo address (::1), which some kind of logic suggests should be the router being at the first stop on the way out, the answer is that this responded to ping from my desktop (i.e. remote) but not from the server (local).

The DUID was a suggestion rather than a statement of fact. Going from the ArchWiki dhcpcd page the part under the heading DHCP Client Identifier appears to emphasise it. But the construction of a DUID looks similar to that of a MAC address, though the MAC is shorter. So I don't know how the addresses were derived.

Neither of the shown IPs responded to ping.

Does any of this shed any further light?

TIA,

Mike

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#4 2020-01-06 16:18:58

rsmarples
Member
Registered: 2009-05-12
Posts: 234

Re: Not picking up SLAAC allocated IPv6 address

$ ip -6 route show  | grep default
default via fe80::1 dev enp1s0 metric 2003  mtu 1492

You should see something like that. fe80::1 is the address of your router.
Your router may also have a public ip address - 2001:bc8:6005:127::1 is likely but not certain. Try and ping that if you can.
If both work then the issue is not with your network setup - could be an issue on the router or firewall.
If either fail, please post your whole routing table.

For what it's worth, I cannot access NetBSD machines from my network using a HE IPv6 tunnel. The rest of the IPv6 connections to the internet work fine though - maybe your issue is simillar to mine. Can you ping known IPv6 hosts such as ipv6.google.com?

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#5 2020-01-06 16:37:36

freshscaped
Member
From: West Yorkshire
Registered: 2015-08-29
Posts: 60

Re: Not picking up SLAAC allocated IPv6 address

Close. I got 2001:bc8:2::5:127:1 as the IP with the initial enquiry, which was pinged successfully from the desktop but not the server.

# ip -6 route show  | grep default
default via fe80::2c8:8bff:fee2:d687 dev enp1s0 proto ra metric 202 mtu 1500 pref medium
default via fe80::2c8:8bff:fee2:d687 dev enp1s0 proto ra metric 20100 pref medium

 ~]# ping fe80::2c8:8bff:fee2:d687
PING fe80::2c8:8bff:fee2:d687(fe80::2c8:8bff:fee2:d687) 56 data bytes
ping: sendmsg: Invalid argument
ping: sendmsg: Invalid argument
ping: sendmsg: Invalid argument
ping: sendmsg: Invalid argument
^C
--- fe80::2c8:8bff:fee2:d687 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3051ms

then from my desktop, similar:

[mike@duke ~]$ ping fe80::2c8:8bff:fee2:d687
PING fe80::2c8:8bff:fee2:d687(fe80::2c8:8bff:fee2:d687) 56 data bytes
ping: sendmsg: Invalid argument
ping: sendmsg: Invalid argument
ping: sendmsg: Invalid argument
^C
--- fe80::2c8:8bff:fee2:d687 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2024ms

So tried G:

~]# ping ipv6.google.com
PING ipv6.google.com(par21s17-in-x0e.1e100.net (2a00:1450:4007:808::200e)) 56 data bytes
^C
--- ipv6.google.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2027ms

No joy there either so route:

~]# ip -6 route
::1 dev lo proto kernel metric 256 pref medium
2001:bc8:2::5:127:1 dev enp1s0 proto ra metric 100 pref medium
2001:bc8:6005:127::/64 dev enp1s0 proto ra metric 100 pref medium
2001:bc8:6005:127::/64 dev enp1s0 proto ra metric 202 mtu 1500 pref medium
fe80::/64 dev enp1s0 proto kernel metric 100 pref medium
default via fe80::2c8:8bff:fee2:d687 dev enp1s0 proto ra metric 202 mtu 1500 pref medium
default via fe80::2c8:8bff:fee2:d687 dev enp1s0 proto ra metric 20100 pref medium

[edit] Since posting I've been running searches to see if I can find what all this means, let alone a solution! The nearest I've come to anything which makes sense (to me, at least) is that the route is incomplete and needs an address or range adding. But what is the address or range to add? And how to do it with v6? All I've seen so far is IPv4. [/edit]

Last edited by freshscaped (2020-01-06 17:33:29)

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#6 2020-01-06 17:53:52

progandy
Member
Registered: 2012-05-17
Posts: 3,650

Re: Not picking up SLAAC allocated IPv6 address

To ping a link-local (fe80::) address, you'll have to add an interface specifier. The kernel doesn't know which interface/link it should use to reach such an address.

ping fe80::2c8:8bff:fee2:d687%enp1s0

Last edited by progandy (2020-01-06 17:54:15)


| alias CUTF='LANG=en_XX.UTF-8@POSIX ' |

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#7 2020-01-06 21:50:19

freshscaped
Member
From: West Yorkshire
Registered: 2015-08-29
Posts: 60

Re: Not picking up SLAAC allocated IPv6 address

Thanks progandy. That's the local working then. And another item added to my growing list of networking tools and tool clip-ons. Very much appreciated.

Mike

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