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groner
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ipv6 dhcp-client failure with no retry and no errors logged

Wed May 04, 2022 11:53 pm

Hi,

I had a loss of ipv6 connectivity on my network today. Investigating (scroll for details), I found
- hosts only have fe80:: addresses
- router only has fe80:: addresses
- no ipv6 address pool
- ipv6 dhcp-client has status=error
- nothing logged by the ipv6 dhcp-client

I use a dhcp-client to request a /60 prefix for my networks. I only use SLAAC for ipv6 address assignments on my LAN. This configuration has been working reliably for several months now.

On finding the dhcp-client with status error, recovery was simply a matter of telling it to renew.

My questions are:
1. Why is nothing logged about this?
2. Shouldn't this be recoverable?

Logs show ipv4 dhcp-client errors from last night, I suspect xfinity was pushing some configuration change to my cable modem. I guess is this is what tripped up the ivp6 dhcp-client, but I don't really know because the logs don't say anything.
 03:15:01 interface,info ether1 link down
 03:15:01 dhcp,info dhcp-client on ether1 lost IP address 98.xxx.xxx.xxx - lease stopped locally
 03:15:18 interface,info ether1 link up (speed 1G, full duplex)
 03:15:24 dhcp,info dhcp-client on ether1 got IP address 192.168.100.11
 03:16:04 dhcp,critical,error dhcp-client on ether1 lost IP address 192.168.100.11 - received NAK from dhcp server 69.xxx.xxx.xxx
 03:16:04 dhcp,info dhcp-client on ether1 got IP address 98.xxx.xxx.xxx
 03:16:08 system,info,account user admin logged out from 192.168.200.33 via web
 03:17:07 interface,info ether1 link down
 03:17:07 dhcp,info dhcp-client on ether1 lost IP address 98.xxx.xxx.xxx - lease stopped locally
 03:17:25 interface,info ether1 link up (speed 1G, full duplex)
 03:17:30 dhcp,info dhcp-client on ether1 got IP address 192.168.100.11
 03:18:10 dhcp,critical,error dhcp-client on ether1 lost IP address 192.168.100.11 - received NAK from dhcp server 69.xxx.xxx.xxx
 03:18:11 dhcp,info dhcp-client on ether1 got IP address 98.xxx.xxx.xxx
Other details:

                   uptime: 14w1d17h48m2s
                  version: 7.1.1 (stable)
               board-name: RB5009UG+S+

[admin@darkness] > /system logging print 
Flags: * - DEFAULT
Columns: TOPICS, ACTION
#   TOPICS    ACTION
0 * info      memory
1 * error     memory
2 * warning   memory
3 * critical  echo                 
Diagnostic and recovery:
[admin@darkness] /ipv6> /ipv6 address print
Flags: I, D - DYNAMIC; G, L - LINK-LOCAL
Columns: ADDRESS, FROM-POOL, INTERFACE, ADVERTISE
#    ADDRESS                       FROM-POOL  INTERFACE   ADVERTISE
;;; address pool error: pool not found: XFINITYv6 (4)
0 IG ::1/64                        XFINITYv6  LOCAL-USER  yes
1 DL fe80::xxxx:xxxx:xxxx:eedf/64             ether1      no
2 DL fe80::xxxx:xxxx:xxxx:eee0/64             bridge      no
3 DL fe80::xxxx:xxxx:xxxx:eee0/64             LOCAL-USER  no
4 DL fe80::xxxx:xxxx:xxxx:eee0/64             MGMT        no

[admin@darkness] /ipv6> /ipv6 dhcp-client print detail
Flags: D - dynamic; X - disabled, I - invalid
 0    interface=ether1 status=error duid="0xabcdabcdabcdabcdabcd" dhcp-server-v6=fe80::xxxx:xxxx:xxxx:a646 request=address,prefix add-default-route=yes default-route-distance=1 use-peer-dns=no dhcp-options="" pool-name="XFINITYv6" pool-prefix-length=64 prefix-hint=::/60 dhcp-options=""

[admin@darkness] /ipv6> /ipv6 dhcp-client renew 0
[admin@darkness] /ipv6> /ipv6 dhcp-client print detail
Flags: D - dynamic; X - disabled, I - invalid
 0    interface=ether1 status=bound duid="0xabcdabcdabcdabcdabcd" dhcp-server-v6=fe80::xxxx:xxxx:xxxx:a646 request=address,prefix add-default-route=yes default-route-distance=1 use-peer-dns=no dhcp-options="" pool-name="XFINITYv6" pool-prefix-length=64 prefix-hint=::/60 dhcp-options=""
      prefix=2601:5c2:201:xxxx::/60, 3d6h4m52s address=2001:558:6036:xxxx:xxxx:xxxx:xxxx:ed73, 3d6h4m52s

[admin@darkness] /ipv6> /ipv6 address print
Flags: D - DYNAMIC; G, L - LINK-LOCAL
Columns: ADDRESS, FROM-POOL, INTERFACE, ADVERTISE
#    ADDRESS                                 FROM-POOL  INTERFACE   ADVERTISE
0  G 2601:5c2:201:xxxx::1/64                 XFINITYv6  LOCAL-USER  yes
1 DL fe80::xxxx:xxxx:xxxx:eedf/64                       ether1      no
2 DL fe80::xxxx:xxxx:xxxx:eee0/64                       bridge      no
3 DL fe80::xxxx:xxxx:xxxx:eee0/64                       LOCAL-USER  no
4 DL fe80::xxxx:xxxx:xxxx:eee0/64                       MGMT        no
5 DG 2001:558:6036:xxxx:xxxx:xxxx:xxxx:ed73/64             ether1      no

 
Sob
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Re: ipv6 dhcp-client failure with no retry and no errors logged

Sat May 07, 2022 2:53 pm

You can enable more detailed DHCP logging, but it's for all DHCP, client, server, DHCPv4, DHCPv6. So most of the time it would fill your logs with tons of useless messages. It's possible that default logging for DHCPv6 client should be revised, but it's probably low on list of priorities.
 
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Re: ipv6 dhcp-client failure with no retry and no errors logged

Sat May 07, 2022 4:17 pm

I've had this issue with Comcast as well where the DHCPv6 client doesn't auto recover on a number of different ROS versions across 6 and 7.

I suspect a packet capture would be needed to figure out which part of the conversation is missing. I've never been able to pin it down because it only happens once or twice a year - which would align with the assumption that it's happening during some kind of maintenance or upgrade.
 
mrteriyaki
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Re: ipv6 dhcp-client failure with no retry and no errors logged

Mon Jul 11, 2022 4:22 pm

I've got the same issues reported here in recent months, I've been running without issue for a couple years.
DHCPv6 client just stuck on 'error' with nothing in the logs, disable and enabling the client will bring it back up, seems to happen every few weeks (could be more frequent and I just haven't noticed).

My DHCPv6 client was in an error state tonight and I was running some packet captures to try and see what it's doing.
By chance it got stuck in the error state again after disabling/enabling the client from a working state while i was still running a capture.

I've attached the captures.
'error-to-working.pcap' - up to packet 26 are the packets while in the error state, packet 26 is the point of manual enable/disable of dhcpv6 client to restore it.
'working-to-error.pcap' - packet 3 is manual disable/enable to restore ipv6 client.

Captures were streamed to wireshark, the router's ipv6 local ip is fe80::ba69:f4ff:fe90:beb2/64 and working-to-error is filtered by dhcpv6/icmpv6.
Running routerboard 3011 w/6.49.5
I'm a pleb with how dhcpv6 works but seems like it's getting stuck if the isp doesn't respond to the last Request XID packets.
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