Revision history [back]

click to hide/show revision 1
initial version

Hello. So let me shed some light on this for you!

Neutron has no built-in mechanism for HA routers in Icehouse and below (Juno has experimental VRRP support). When you schedule a router, it schedules to an l3_agent. You can run multiple l3_agents, but a router can only associate with a single l3_agent.

Again, there is _no_ built-in mechanism to transfer routers from l3_agent to another. This means when an l3_agent is down, the routers are down until that agent comes back up. Period. To solve this problem, there are 3rd party scripts designed to move these routers at the database level from one l3_agent to a seperate l3_agent. At&t has one I would recommend, it works very well.

So the procedure would look like this.

network01 and network02 both have active _different_ l3_agents.
EVENT: network01 l3_agent goes down
TRIGGERS: failover script to tweak the database, moves routers from one agent to a different agent
EVENT: network01 l3_agent comes back up
(Trigger or don't it depends on your configuration)

Also, you can and should run multiple dhcp_agents for the same network. They can be natively HA due to the nature of DHCP and the fact leases are both race to return stored in a database.

Do you have any additional questions on this confusing subject?

Hello. So let me shed some light on this for you!

Neutron has no built-in mechanism for HA routers in Icehouse and below (Juno has experimental VRRP support). When you schedule a router, it schedules to an l3_agent. You can run multiple l3_agents, but a router can only associate with a single l3_agent.

Again, there is _no_ built-in mechanism to transfer routers from l3_agent to another. This means when an l3_agent is down, the routers are down until that agent comes back up. Period. To solve this problem, there are 3rd party scripts designed to move these routers at the database level from one l3_agent to a seperate l3_agent. At&t has one I would recommend, it works very well.

So the procedure would look like this.

network01 and network02 both have active _different_ l3_agents.
EVENT: network01 l3_agent goes down
TRIGGERS: failover script to tweak the database, moves routers from one agent to a different agent
EVENT: network01 l3_agent comes back up
(Trigger or don't it depends on your configuration)

Also, you can and should run multiple dhcp_agents for the same network. They can be natively HA due to the nature of DHCP and the fact leases are stored in a database. The both race to return stored in a database. the same address, so no conflict.

Do you have any additional questions on this confusing subject?