Public bug reported: Bug originally reported for RHOSP: https://bugzilla.redhat.com/show_bug.cgi?id=1651647 by Alex Stupnikov. Original description:
It is possible to create two subnets for single external network and it looks like we support such kind of setup. However, it doesn't work properly: every DVR will have a single on-link route for ONLY ONE external subnet and will not have on-link route for another one. As a result, there are two scenarios when routing doesn't work as it should: - two instances with FIPs from different external subnets will have asymmetric traffic flows: if there is an on-link route for DST packet, it will be routed directly to another DVR. If not, packet will be routed to external router. As a result, if there is a stateful firewall on external router, this communication will be blocked. - two instances with FIPs from the same external subnet could have suboptimal traffic flows if there are no on-link routes for this subnet. As a result, traffic will always go through external router, which could cause issues if router has protection against such kind of flows. Here is an example output of routing table in fip-* namespace on compute node where single external network has two subnets: 10.0.0.0/24 and 10.0.1.0/24: default via 10.0.0.1 dev fg-83ec5f16-be table 2852022899 10.0.0.0/24 dev fg-83ec5f16-be proto kernel scope link src 10.0.0.225 10.0.0.218 via 169.254.106.114 dev fpr-789f245b-1 10.0.0.219 via 169.254.106.114 dev fpr-789f245b-1 10.0.1.15 via 169.254.106.114 dev fpr-789f245b-1 As we can see, there are host routes for local FIPs, a single on-link route for 10.0.0.0/24 subnet and default route. Additional information: An upstream bug for legacy routers [1] was solved long time ago. [1] https://bugs.launchpad.net/neutron/+bug/1312467 ** Affects: neutron Importance: Medium Assignee: Slawek Kaplonski (slaweq) Status: Confirmed ** Tags: l3-dvr-backlog -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to neutron. https://bugs.launchpad.net/bugs/1805456 Title: [DVR] Neutron doesn't configure multiple external subnets for one network properly Status in neutron: Confirmed Bug description: Bug originally reported for RHOSP: https://bugzilla.redhat.com/show_bug.cgi?id=1651647 by Alex Stupnikov. Original description: It is possible to create two subnets for single external network and it looks like we support such kind of setup. However, it doesn't work properly: every DVR will have a single on-link route for ONLY ONE external subnet and will not have on-link route for another one. As a result, there are two scenarios when routing doesn't work as it should: - two instances with FIPs from different external subnets will have asymmetric traffic flows: if there is an on-link route for DST packet, it will be routed directly to another DVR. If not, packet will be routed to external router. As a result, if there is a stateful firewall on external router, this communication will be blocked. - two instances with FIPs from the same external subnet could have suboptimal traffic flows if there are no on-link routes for this subnet. As a result, traffic will always go through external router, which could cause issues if router has protection against such kind of flows. Here is an example output of routing table in fip-* namespace on compute node where single external network has two subnets: 10.0.0.0/24 and 10.0.1.0/24: default via 10.0.0.1 dev fg-83ec5f16-be table 2852022899 10.0.0.0/24 dev fg-83ec5f16-be proto kernel scope link src 10.0.0.225 10.0.0.218 via 169.254.106.114 dev fpr-789f245b-1 10.0.0.219 via 169.254.106.114 dev fpr-789f245b-1 10.0.1.15 via 169.254.106.114 dev fpr-789f245b-1 As we can see, there are host routes for local FIPs, a single on-link route for 10.0.0.0/24 subnet and default route. Additional information: An upstream bug for legacy routers [1] was solved long time ago. [1] https://bugs.launchpad.net/neutron/+bug/1312467 To manage notifications about this bug go to: https://bugs.launchpad.net/neutron/+bug/1805456/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : [email protected] Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
