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[mark zhang <1928738@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Consult with one problem: 
I'm not sure, if there already exist enhancement for such scenario.
Please help check, how to update router the new MAC by GARP with arp_responder enabled, thanks a lot.

Problem scenario openstack with neutron:
1. VM A and VM B works in active-standby mode, with one floating IP.
2. If VM A, is one active one, then the floating IP is resident on the VM A.
3. If switchover happened, the floating IP will be added into VM B, and VM B will send-out GARP to update the router, the IP resident on new MAC now.
4. But with arp_responder enabled, the GARP couldn't reach to router.


[root@overcloud-ovscompute-pl-36-4 ~]# grep -r 'arp_responder' /var/lib/config-data/neutron/
/var/lib/config-data/neutron/etc/neutron/plugins/ml2/openvswitch_agent.ini:arp_responder=True
/var/lib/config-data/neutron/etc/puppet/hieradata/ovscompute_extraconfig.json:    "neutron::agents::ml2::ovs::arp_responde ": true
/var/lib/config-data/neutron/etc/puppet/hieradata/service_configs.json:    "neutron::agents::ml2::ovs::arp_responder": true,


tcpdump in VM level when VM switchover happened; (10.0.0.7 is one floating IP, fa:16:3e:b6:d7:5c is the MAC of VM B, fa:16:3e:63:d0:39 is the MAC of VM A).
07:43:14.216913 ARP, Request who-has 10.0.0.7 (Broadcast) tell 10.0.0.7, length 28
07:43:14.216939 ARP, Reply 10.0.0.7 is-at fa:16:3e:b6:d7:5c, length 28
07:43:14.217131 ARP, Reply 10.0.0.7 is-at fa:16:3e:63:d0:39, length 28
07:43:14.217155 ARP, Reply 10.0.0.7 is-at fa:16:3e:63:d0:39, length 28


Thanks,
Mark

** Affects: neutron
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1928738

Title:
  Arp_responder: two VMs share one floating IP, but the arp table not
  updated with GARP.

Status in neutron:
  New

Bug description:
  Consult with one problem: 
  I'm not sure, if there already exist enhancement for such scenario.
  Please help check, how to update router the new MAC by GARP with arp_responder enabled, thanks a lot.

  Problem scenario openstack with neutron:
  1. VM A and VM B works in active-standby mode, with one floating IP.
  2. If VM A, is one active one, then the floating IP is resident on the VM A.
  3. If switchover happened, the floating IP will be added into VM B, and VM B will send-out GARP to update the router, the IP resident on new MAC now.
  4. But with arp_responder enabled, the GARP couldn't reach to router.

  
  [root@overcloud-ovscompute-pl-36-4 ~]# grep -r 'arp_responder' /var/lib/config-data/neutron/
  /var/lib/config-data/neutron/etc/neutron/plugins/ml2/openvswitch_agent.ini:arp_responder=True
  /var/lib/config-data/neutron/etc/puppet/hieradata/ovscompute_extraconfig.json:    "neutron::agents::ml2::ovs::arp_responde ": true
  /var/lib/config-data/neutron/etc/puppet/hieradata/service_configs.json:    "neutron::agents::ml2::ovs::arp_responder": true,

  
  tcpdump in VM level when VM switchover happened; (10.0.0.7 is one floating IP, fa:16:3e:b6:d7:5c is the MAC of VM B, fa:16:3e:63:d0:39 is the MAC of VM A).
  07:43:14.216913 ARP, Request who-has 10.0.0.7 (Broadcast) tell 10.0.0.7, length 28
  07:43:14.216939 ARP, Reply 10.0.0.7 is-at fa:16:3e:b6:d7:5c, length 28
  07:43:14.217131 ARP, Reply 10.0.0.7 is-at fa:16:3e:63:d0:39, length 28
  07:43:14.217155 ARP, Reply 10.0.0.7 is-at fa:16:3e:63:d0:39, length 28


  Thanks,
  Mark

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