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Re: Gateway disappears on IPv6



Am Montag, 10. Juli 2017, 10:24:43 CEST schrieb Rainer Dorsch:

> Hi,

>

> I added a IPv6 support to a KVM virtualized Jessie system following the

> instructions by the hoster

>

> https://www.netcup-wiki.de/wiki/Zus

> %c3%a4tzliche_IP_Adresse_konfigurieren#IPv6%7C

>

> I my case, I added

>

> (for me it looks a little weird that IPv4 gets configured via dhcp and IPv6

> is a static configuration, but that is how I read the information in the

> wiki.

>

> After rebooting the system works nicely and shows ipv6 addresses and a

> routing table

>

> root@netcup:~# ip -6 addr show

> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536

> inet6 ::1/128 scope host

> valid_lft forever preferred_lft forever

> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000

> inet6 2a03:4000:6:52b6::/64 scope global

> valid_lft forever preferred_lft forever

> inet6 fe80::5054:9cff:fe31:f1e0/64 scope link

> valid_lft forever preferred_lft forever

> root@netcup:~# /sbin/route -6

> Kernel IPv6 routing table

> Destination Next Hop Flag Met Ref Use

> If

> ::1/128 :: U 256 0 0

> ::lo

>

> 2a03:4000:6:52b6::/64 :: U 256 0 0

> eth0

> fe80::/64 :: U 256 0 0

> eth0

>

> ::/0 fe80::1 UGDAe 1024 3 0

>

> eth0

>

> ::/0 :: !n -1 1 163

> ::lo

> ::1/128 :: Un 0 1 36

> ::lo

>

> 2a03:4000:6:52b6::/128 :: Un 0 7 14

> lo fe80::5054:9cff:fe31:f1e0/128 :: Un 0 1

> 5 lo ff00::/8 :: U 256 10

> 0 eth0

>

> ::/0 :: !n -1 1 163

> ::lo

>

> root@netcup:~#

>

> After some time (at least hours) the server is not reachable anymore on its

> IPv6 address, when connecting on the IPv4 address it seems that the gateway

> fe80::1 got lost:

>

> root@netcup:~# ip -6 addr show

> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536

> inet6 ::1/128 scope host

> valid_lft forever preferred_lft forever

> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000

> inet6 2a03:4000:6:52b6::/64 scope global

> valid_lft forever preferred_lft forever

> inet6 fe80::5054:9cff:fe31:f1e0/64 scope link

> valid_lft forever preferred_lft forever

> root@netcup:~# /sbin/route -6

> Kernel IPv6 routing table

> Destination Next Hop Flag Met Ref Use

> If

> ::1/128 :: U 256 0 0

> ::lo

>

> 2a03:4000:6:52b6::/64 :: U 256 0 0

> eth0

> fe80::/64 :: U 256 0 0

> eth0

>

> ::/0 :: !n -1 1 3321

> ::lo

> ::1/128 :: Un 0 1 270

> ::lo

>

> 2a03:4000:6:52b6::/128 :: Un 0 2 670

> lo fe80::5054:9cff:fe31:f1e0/128 :: Un 0 1

> 34 lo ff00::/8 :: U 256 12

> 0 eth0

>

> ::/0 :: !n -1 1 3321

> ::lo

>

> root@netcup:~#

>

> Rebooting restores the routing table and makes IPv6 working again.

>

> Has anybody an idea what is going wrong here? Any hint is welcome.

>

 

I wrote a script to detect when the unexpected route change happens:

 

rd@netcup:~$ cat ip6-test.sh
#!/bin/sh

while :
do
   if ! ping6 -c1 -W1 home.bokomoko.de > /dev/null; then
       echo `date`, connection lost >> /tmp/ipv6.log
   else
       echo `date`, connection ok >> /tmp/ipv6.log
   fi
   sleep 30
done
rd@netcup:~$

Interesting enough around the time when the ipv6 network becomes unreachable

 

Wed Jul 12 23:03:59 CEST 2017, connection ok

Wed Jul 12 23:04:29 CEST 2017, connection ok

Wed Jul 12 23:04:59 CEST 2017, connection lost

Wed Jul 12 23:05:29 CEST 2017, connection lost

Wed Jul 12 23:05:59 CEST 2017, connection lost

 

there is no remotely relevant entry (except spam scanner, clamav, etc) in /var/log/syslog

 

Jul 12 23:03:35 netcup spamd[1413]: spamd: connection from localhost [127.0.0.1]:51620 to port 783, fd 5
Jul 12 23:03:35 netcup spamd[1413]: spamd: setuid to Debian-exim succeeded
Jul 12 23:03:35 netcup spamd[1413]: spamd: checking message <CABVU7+sMc6LOR6hm==OF6LDP+qFBVGO9qcC0O2VEfLq6DnGzwg@mail.gmail.com> for Debian-exim:101
Jul 12 23:03:38 netcup spamd[1413]: spamd: clean message (-1.3/5.0) for Debian-exim:101 in 3.2 seconds, 62490 bytes.
Jul 12 23:03:38 netcup spamd[1413]: spamd: result: . -1 - FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_MED,RP_MATCHES_RCVD,T_DKIM_INVALID,U
RIBL_BLOCKED,URIBL_SBL,URIBL_SBL_A scantime=3.2,size=62490,user=Debian-exim,uid=101,required_score=5.0,rhost=localhost,raddr=127.0.0.1,rport=51620,mid=<CABVU7+sMc6LOR6hm==OF6LDP+q
FBVGO9qcC0O2VEfLq6DnGzwg@mail.gmail.com>,autolearn=ham autolearn_force=no
Jul 12 23:03:38 netcup spamd[1326]: prefork: child states: II
Jul 12 23:05:01 netcup CRON[2310]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)
Jul 12 23:07:31 netcup spamd[1413]: spamd: connection from localhost [127.0.0.1]:51651 to port 783, fd 5
Jul 12 23:07:31 netcup spamd[1413]: spamd: setuid to Debian-exim succeeded
Jul 12 23:07:31 netcup spamd[1413]: spamd: checking message <CABVU7+uS=VgisZxrRAQ5Z9UL2TonvcAjhHFbVNOMGY6sVCkmQQ@mail.gmail.com> for Debian-exim:101
Jul 12 23:07:34 netcup spamd[1413]: spamd: clean message (-2.1/5.0) for Debian-exim:101 in 2.7 seconds, 7870 bytes.
Jul 12 23:07:34 netcup spamd[1413]: spamd: result: . -2 - FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_MED,RP_MATCHES_RCVD,T_DKIM_INVALID,U
RIBL_BLOCKED scantime=2.7,size=7870,user=Debian-exim,uid=101,required_score=5.0,rhost=localhost,raddr=127.0.0.1,rport=51651,mid=<CABVU7+uS=VgisZxrRAQ5Z9UL2TonvcAjhHFbVNOMGY6sVCkmQ
Q@mail.gmail.com>,autolearn=ham autolearn_force=no
Jul 12 23:07:34 netcup spamd[1326]: prefork: child states: II

I am surprised that a route change does not show up in syslog, is there any other logfile where a log entry is expected? If not, is it possible to add a log entry by changing a log verbosity level, if yes, in which configuration file?

 

Many thanks again

Rainer

 

 

 

 

 

--

Rainer Dorsch

http://bokomoko.de/


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