There are four main high availability networking options for OpenStack: 1) Using external hardware gateways to offload networking HA, 2) Configuring VMs with multi-NICs on separate networks for failover, 3) Enabling a 4-second failover between network hosts, and 4) Configuring each compute host to handle networking for its own VMs to eliminate single points of failure in networking hosts.

1. High Availability Networking - Openstack

2. HA Option 1: Hardware gateway
• Benefits
– The dnsmasqservice can be configured to use an external gateway
insteadof acting as the gatewayfor the VMs
– This offloads HA to standard switching hardware and it has some
strong benefits
• Limitations
– the nova-network service is still responsible for floating IP natting and
DHCP, so some failover strategy needs to be employed for those
options

3. • Configuration
 Create a dnsmasqconfiguration file (e.g., /etc/dnsmasq-nova.conf)
that contains the IP address of the external gateway
dhcp-option=option:router,172.16.100.1
 Edit /etc/nova/nova.conf to specify the location of the dnsmasq
configuration file:
dnsmasq_config_file=/etc/dnsmasq-nova.conf
 Configure the hardware gatewayto forward metadatarequests to a
hostthat's running the nova-api service with the metadataAPI
enabled.
enabled_apis=ec2,osapi_compute,osapi_volume,metadata
 Ensure you have set up routes properly so that the subnet that you
use for virtual machines is routable.

4. HA Option 2: Multi-Nic
• Benefits
– Nova gained support for multi-nic. This allows us to bridge a given VM
into multiple networks. This gives us some more options for high
availability
– It is possible to set up two networks on separate vlans (or even
separate Ethernet devices on the host) and give the VMs a NIC and an
IPon each network
• Limitations
– this approach is it offloads managementof failure scenarios to the
guest.
– The guest needs to be aware of multiple networks and have a strategy
for switching between them. It also doesn't help with floating IPs.

5. HA Option 3: Failover
• Benefits
– The folks at NTT labs came up with a ha-linux configuration that allows
for a 4 second failover to a hot backup of the network host
• Limitation
– Not suitable for some real-time applications those having SLA less
than 4 seconds
• Configuration
– To enable this HA option, your nova.conf file mustcontain the
following option:
send_arp_for_ha=True

6. HA Option 4: Multi-host
• Benefits
– To eliminate the network host as a single point of failure, Compute can be configured to
allow each compute host to do all of the networking jobs for its own VMs.
– Each compute host does NAT, DHCP, and acts as a gateway for all of its own VMs. While
there is still a single point of failure in this scenario, it is the same point of failure that
applies to all virtualized systems.
• Configuration
– To run in HA mode, each compute host must run the following services:
• nova-compute
• nova-network
• nova-api-metadata or nova-api

7. High Availability Networking Option