[openstack-dev] [neutron] neutron ipv6 radvd sends out link-local or nothing as def gw (L3 HA issue?)

Tobias Urdin tobias.urdin at binero.se
Mon Aug 20 09:50:44 UTC 2018


Ok, so the issue here seems to be that I have a L3 HA router with SLAAC, 
both the active and standby router will
configure the SLAAC obtained address causing a conflict since both side 
share the same MAC address.

Is there any workaround for this? Should SLAAC even be enabled for 
interfaces on the standby router?

Best regards
Tobias

On 08/20/2018 11:37 AM, Tobias Urdin wrote:
> Forgot [neutron] tag.
>
> On 08/20/2018 11:36 AM, Tobias Urdin wrote:
>> Hello,
>>
>> Note: before reading, this router was a regular router but was then 
>> disable, changed ha=true so it's now a L3 HA router, then it was 
>> enabled again.
>> CC openstack-dev for help or feedback if it's a possible bug.
>>
>> I've been testing around with IPv6 and overall the experience has 
>> been positive but I've met some weird issue that I cannot put my head 
>> around.
>> So this is a neutron L3 router with an outside interface with a ipv4 
>> and ipv6 from the provider network and one inside interface for ipv4 
>> and one inside interface for ipv6.
>>
>> The instances for some reason get's there default gateway as the ipv6 
>> link-local (in fe80::/10) from the router with SLAAC and radvd.
>>
>> (1111.2222 is provider network, 1111.4444 is inside network, they are 
>> masked so don't pay attention to the number per se)
>>
>> *interfaces inside router:*
>> 15: ha-9bde1bb1-bd: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc 
>> noqueue state UNKNOWN group default qlen 1000
>>     link/ether fa:16:3e:05:80:32 brd ff:ff:ff:ff:ff:ff
>>     inet 169.254.192.7/18 brd 169.254.255.255 scope global ha-9bde1bb1-bd
>>        valid_lft forever preferred_lft forever
>>     inet 169.254.0.1/24 scope global ha-9bde1bb1-bd
>>        valid_lft forever preferred_lft forever
>>     inet6 fe80::f816:3eff:fe05:8032/64 scope link
>>        valid_lft forever preferred_lft forever
>> 19: qg-86e465f6-33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc 
>> noqueue state UNKNOWN group default qlen 1000
>>     link/ether fa:16:3e:3b:8b:a5 brd ff:ff:ff:ff:ff:ff
>>     inet 1.2.3.4/22 scope global qg-86e465f6-33
>>        valid_lft forever preferred_lft forever
>>     inet6 1111:2222::f/64 scope global nodad
>>        valid_lft forever preferred_lft forever
>>     inet6 fe80::f816:3eff:fe3b:8ba5/64 scope link nodad
>>        valid_lft forever preferred_lft forever
>> 1168: qr-5be04815-68: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 
>> qdisc noqueue state UNKNOWN group default qlen 1000
>>     link/ether fa:16:3e:c3:85:bd brd ff:ff:ff:ff:ff:ff
>>     inet 192.168.99.1/24 scope global qr-5be04815-68
>>        valid_lft forever preferred_lft forever
>>     inet6 fe80::f816:3eff:fec3:85bd/64 scope link
>>        valid_lft forever preferred_lft forever
>> 1169: qr-7fad6b1b-c9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 
>> qdisc noqueue state UNKNOWN group default qlen 1000
>>     link/ether fa:16:3e:66:de:a8 brd ff:ff:ff:ff:ff:ff
>>     inet6 1111:4444:0:1::1/64 scope global nodad
>>        valid_lft forever preferred_lft forever
>>     inet6 fe80::f816:3eff:fe66:dea8/64 scope link
>>        valid_lft forever preferred_lft forever
>>
>> I get this error messages in dmesg on the network node:
>> [581085.858869] IPv6: qr-5be04815-68: IPv6 duplicate address 
>> 1111:4444:0:1:f816:3eff:fec3:85bd detected!
>> [581085.997497] IPv6: qr-7fad6b1b-c9: IPv6 duplicate address 
>> 1111:4444:0:1:f816:3eff:fe66:dea8 detected!
>> [581142.869939] IPv6: qr-5be04815-68: IPv6 duplicate address 
>> 1111:4444:0:1:f816:3eff:fec3:85bd detected!
>> [581143.182371] IPv6: qr-7fad6b1b-c9: IPv6 duplicate address 
>> 1111:4444:0:1:f816:3eff:fe66:dea8 detected!
>>
>> *radvd:*
>> interface qr-7fad6b1b-c9
>> {
>>    AdvSendAdvert on;
>>    MinRtrAdvInterval 30;
>>    MaxRtrAdvInterval 100;
>>
>>    AdvLinkMTU 1450;
>>
>>    RDNSS  2001:4860:4860::8888  {};
>>
>>    prefix 1111:4444:0:1::/64
>>    {
>>         AdvOnLink on;
>>         AdvAutonomous on;
>>    };
>> };
>>
>> *inside instance:*
>> ipv4 = 192.168.199.7
>> ipv6 = 1111:4444:0:1:f816:3eff:fe29:723d/64 (from radvd SLAAC)
>>
>> I can ping ipv4 gateway 192.168.199.1 and internet over ipv4.
>> I can ping ipv6 gateway 1111:4444:0:1::1 but I can't ping the internet
>>
>> checking the ipv6 routing table on my instance I either get no 
>> default gateway at all or I get a default gateway to a fe80::/10 
>> link-local address.
>> IIRC this worked before I changed the router to a L3 HA router.
>>
>> Appreciate any feedback!
>>
>> Best regards
>> Tobias
>

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