[Dnsmasq-discuss] dnsmasq 2.78 is failing to respond to dhcpv6 requests forwarded via relay agent

Sandeep K M sandeep.matada at gmail.com
Mon Jan 7 07:39:11 GMT 2019


Hi,

As you suggested I added the IPv6 address 2020::2/120 manually to my client
using the below command:

*ip -6 addr add 2020::2/120 dev eth1*

when I pinged the server it failed :




*root at Ubuntu3481:~# ping6 -I 2020::2 1040::2PING 1040::2(1040::2) from
2020::2 : 56 data bytesping: sendmsg: Network is unreachableping: sendmsg:
Network is unreachale*

Then I added a default route:






*root at Ubuntu3481:~# ip -6 route add default via 2020::1root at Ubuntu3481:~#
ip -6 route2020::/120 dev eth1  proto kernel  metric 256fe80::/64 dev eth0
proto kernel  metric 256fe80::/64 dev eth1  proto kernel  metric 256default
via 2020::1 dev eth1  metric 1024*

I see the ping is working fine now:





*root at Ubuntu3481:~# ping6 -I 2020::2 1040::2PING 1040::2(1040::2) from
2020::2 : 56 data bytes64 bytes from 1040::2: icmp_seq=1 ttl=63 time=0.278
ms64 bytes from 1040::2: icmp_seq=2 ttl=63 time=0.178 ms64 bytes from
1040::2: icmp_seq=3 ttl=63 time=0.172 ms*

But when I remove the manually configured IPv6 address and try to get a new
IPv6 using "dhclient -6 eth1" again it fails. I see the same log lines in
dnsmasq log:

Jan  7 07:19:54 dnsmasq-dhcp[3815]: DHCPSOLICIT(m1s1p7)
00:01:00:01:23:c5:ba:1b:00:50:56:96:d1:7c
Jan  7 07:19:54 dnsmasq-dhcp[3815]: DHCPADVERTISE(m1s1p7) 2020::19
00:01:00:01:23:c5:ba:1b:00:50:56:96:d1:7c
Jan  7 07:19:55 dnsmasq-dhcp[3815]: DHCPSOLICIT(m1s1p7)
00:01:00:01:23:c5:ba:1b:00:50:56:96:d1:7c
Jan  7 07:19:55 dnsmasq-dhcp[3815]: DHCPADVERTISE(m1s1p7) 2020::19
00:01:00:01:23:c5:ba:1b:00:50:56:96:d1:7c

When we have enable-ra configured wont dnsmasq advertise the gateway IP's ?
Do we need to enable RA even in the switch where relay agent is running ?
can we configure default gateway to the clients via dhcpv6 options similar
to IPv4 ?


*PS: If I replace dnsmasq server with ISC DHCP server everything works
fine.*

Thanks
-Sandeep




On Fri, Jan 4, 2019 at 7:32 PM Geert Stappers <stappers at hendrikx-itc.nl>
wrote:

> On Fri, Jan 04, 2019 at 05:34:03PM +0530, Sandeep K M wrote:
> > Hi,
> >
> > On Fri, Jan 4, 2019 at 3:59 PM Geert Stappers wrote:
> > > On Fri, Jan 04, 2019 at 02:47:11PM +0530, Sandeep K M wrote:
> > > > On Fri, Jan 4, 2019 at 2:30 PM Geert Stappers wrote:
> > > > > On Fri, Jan 04, 2019 at 11:55:49AM +0530, Sandeep K M wrote:
> > > > > > [ .... ]
> > > > > > Please let me know if any other information is required.
> > > > >
> > > > > At the server
> > > > >   ip link       # what interfaces are there
> > > > >   ip -6 address
> > > > >   ip -6 route
> > > >
> > > > Here are the output of the commands:
> > > >
> > > > root at 8320:~# *ip -6 addr*
> > > > 49: m1s1p7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UNKNOWN
> qlen 1000
> > > >     inet6 1040::2/120 scope global
> > > >        valid_lft forever preferred_lft forever
> > > >     inet6 fe80::480f:cf00:7af:8444/64 scope link
> > > >        valid_lft forever preferred_lft forever
> > >
> > > Based upon that: there is only 1 interface
>
> But it are about sixty
>
>
> > > > root at 8320:~# *ip -6 route*
> > > > 1040::/120 dev m1s1p7  proto kernel  metric 256  pref medium
> > > > 2020::/120 via 1040::1 dev m1s1p7  proto static  metric 512  pref
> medium
> > >
> > > So there is some kind of routing information where the 2020::/120
> network
> > > is ...
> > >
>
> In the non-stripped version
> > fe80::/64 dev bridge-vrf  proto kernel  metric 256  pref medium
> > fe80::/64 dev tap0  proto kernel  metric 256  pref medium
> > fe80::/64 dev tap-br0  proto kernel  metric 256  pref medium
> > fe80::/64 dev m1s1p7  proto kernel  metric 256  pref medium
> (do notice there is no default route)
>
> > > > Sorry forgot to capture "ip link" output. The setup is disassembled
> as of
> > > > now but if it is required then I will recreate the setup and send
> you the
> > > > output.
> > >
> > > Come again?
> > > As in: "How was the output of `ip -6 addr` and `ip -6 route`
> generated?"
> > >
> > These command output is what I have captured previously for my reference
> > before dissembling the setup.
>
> OK. Thanks for explaining.
>
> > *I have recreated the setup and attached (ip-command-output.txt) is the
> > output of the commands that you have requested in full*.
>
> > Please let me know if any other information is needed.
>
> Not yet mentioned in this thread is working connectity between "server"
> and "client".  This will require temporary manual configuration
> of an IPv6 address at client. Let say it is 2020::2/120.
> Then verify with more than "ping". Example given:  `ssh 1040::2`
>
> It shall reveal how well router ( with the odd name 'Switch' ) is
> configured for routing between 1040::/120 and 2020::/120.
> Also if the ssh deamon is able to send packets out on the right
> interface.
>
> I do know that it might seem a detour. And we also known that
> original poster is already stuck with current setup. So the "detour"
> could be a step forward.   Good luck.
>
>
> Groeten
> Geert Stappers
>
>
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>
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