Re: [Openstack-operators] Neutron DHCP agent local routes
Hi Neil, Well that explains... My networking setup does not conform to the commit message in such a way that there are multiple subnets on the network, however the instance does not have an IP address in all of them but only in one. I guess the only option for now is to patch this code, as a workaround.The reason for having multiple subnets on the same L2 segment is a migration scenario. So I guess I'll just patch this as the situation will disappear in the near future as normally subnets are separated by L2 domains (vlans) in our setup. Thanks! Remco On Fri, Apr 22, 2016 at 1:16 PM, Neil Jerram wrote: > On 22/04/16 12:03, Remco wrote: > > Hi Neil, > > > > Thanks. > > The ip route output is as following, i guess the 0.0.0.0 gateway is only > > listed by cloud-init: > > > > debian@instance:/$ ip route > > default via 192.168.10.1 dev eth0 > > 192.168.10.0/24 <http://192.168.10.0/24> dev eth0 scope link > > 169.254.169.254 via 192.168.10.1 dev eth0 > > 192.168.11.0/24 <http://192.168.11.0/24> dev eth0 scope link > > 192.168.12.0/24 <http://192.168.12.0/24> dev eth0 proto kernel scope > > link src 192.168.10.2 > > > > (ip addresses are altered for security reasons). > > Thanks for these clarifications. > > > I'm not sure what creates these routes. I have two suspects: cloud-init > > and DHCP. As the same issue is observed on instances without cloud-init > > this rules out cloud-init. > > We see the same issue on both Windows and Linux instances. > > OK, I think you're seeing the effect of this DHCP agent code, from > neutron/agent/linux/dhcp.py: > > host_routes.extend(["%s,0.0.0.0" % (s.cidr) for s in > self.network.subnets > if (s.ip_version == 4 and > s.cidr != subnet.cidr)]) > > AFAICS there is no obvious knob for suppressing this logic. > > The code was added in commit 6dce817c7c2, and the commit message says: > > =8<= > Provide routes for neighbor IPv4 subnets > > Network may contain several Subnets. In this case all these subnets are > accessible via same link and two VMs with addresses from different > Subnets may talk to each other directly, bypassing default router. For > this to work, "neighbour Subnets" should have entry in VM's routing > tables. RFC3442 describes this situation: > > In some cases more than one IP subnet may be configured on a link. > In such cases, a host whose IP address is in one IP subnet in the > link could communicate directly with a host whose IP address is in a > different IP subnet on the same link. In cases where a client is > being assigned an IP address on an IP subnet on such a link, for each > IP subnet in the link other than the IP subnet on which the client > has been assigned the DHCP server MAY be configured to specify a > router IP address of 0.0.0.0. > > When network contains more that one IPv4 subnets, report these subnets > in 'classless-static-routes' DHCP option. > > DocImpact > > Change-Id: Ifcf1d99e0f0136bf52b8d13675b7ccfd48005fab > Closes-Bug: #1372885 > =8<= > > So I guess the next question is: in what way does your networking setup > not conform to the assumptions in that commit message? > > Regards, > Neil > > ___ OpenStack-operators mailing list OpenStack-operators@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
Re: [Openstack-operators] Neutron DHCP agent local routes
Hi Neil, Thanks. The ip route output is as following, i guess the 0.0.0.0 gateway is only listed by cloud-init: debian@instance:/$ ip route default via 192.168.10.1 dev eth0 192.168.10.0/24 dev eth0 scope link 169.254.169.254 via 192.168.10.1 dev eth0 192.168.11.0/24 dev eth0 scope link 192.168.12.0/24 dev eth0 proto kernel scope link src 192.168.10.2 (ip addresses are altered for security reasons). I'm not sure what creates these routes. I have two suspects: cloud-init and DHCP. As the same issue is observed on instances without cloud-init this rules out cloud-init. We see the same issue on both Windows and Linux instances. We do not have host routes in the subnet config. Thanks, Remco. On Fri, Apr 22, 2016 at 12:06 PM, Neil Jerram wrote: > On 22/04/16 10:59, Remco wrote: > > Hi, > > Hi Remco, > > > We are running Liberty, with provider networks. We use the Neutron DHCP > > agent to configure IPv4 and IPv6 addresses for instances. This is all > > working great, however we sometimes need to put multiple subnets on one > > VLAN interface (for legacy reasons). This is in fact also working, > > however it configures some unwanted routes. > > > > For example, the following subnets exist in a Neutron network: > > > > 192.168.10.0/24 <http://192.168.10.0/24> > > 192.168.11.0/24 <http://192.168.11.0/24> > > 192.168.12.0/24 <http://192.168.12.0/24> > > > > I.e. if the IP address obtained is 192.168.10.8/24 > > <http://192.168.10.8/24>, the following routes are inserted: > > Do you mean on the instance? > > > 192.168.10.0/24 <http://192.168.10.0/24> with gateway 0.0.0.0 > > 192.168.11.0/24 <http://192.168.11.0/24> with gateway 0.0.0.0 > > 192.168.12.0/24 <http://192.168.12.0/24> with gateway 0.0.0.0 > > Does 'with gateway 0.0.0.0' mean directly connected? What precisely > does 'ip r' show? > > (I've never seen, e.g., '192.168.10.0/24 via 0.0.0.0' before, and don't > know how I would interpret that. So guessing you mean '192.168.10.0/24 > dev eth0'.) > > > The first route is obviously not an issue, as this route is directly > > connected, but the other routes are plain wrong and stop traffic from > > being routed to the default gateway. > > > > Does anyone know how to disable this behavior? I only want a default > > gateway obtained from DHCP and I do not need any further routes. > > Do you know what is creating the .11 and .12 routes? Unless you have > host routes in your subnet config, I would expect the instance only to > create a route for its DHCP-issued address, and hence only for .10. > > Neil > > > ___ OpenStack-operators mailing list OpenStack-operators@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
[Openstack-operators] Neutron DHCP agent local routes
Hi, We are running Liberty, with provider networks. We use the Neutron DHCP agent to configure IPv4 and IPv6 addresses for instances. This is all working great, however we sometimes need to put multiple subnets on one VLAN interface (for legacy reasons). This is in fact also working, however it configures some unwanted routes. For example, the following subnets exist in a Neutron network: 192.168.10.0/24 192.168.11.0/24 192.168.12.0/24 I.e. if the IP address obtained is 192.168.10.8/24, the following routes are inserted: 192.168.10.0/24 with gateway 0.0.0.0 192.168.11.0/24 with gateway 0.0.0.0 192.168.12.0/24 with gateway 0.0.0.0 The first route is obviously not an issue, as this route is directly connected, but the other routes are plain wrong and stop traffic from being routed to the default gateway. Does anyone know how to disable this behavior? I only want a default gateway obtained from DHCP and I do not need any further routes. Thanks, Remco ___ OpenStack-operators mailing list OpenStack-operators@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
