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How To Configure Redundancy to a Cloud with a Remote IP Using a Static route with a Probe

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TitleHow To Configure Redundancy to a Cloud with a Remote IP Using a Static route with a Probe
Objective
Servers are hosted on a subnet in the cloud that has a primary and backup IP tunnel address, and the network provides a connection to each.

The two routers connect to separate default gateways and have a connection between them for redundancy.
The EOS routers are using OSPF between each other and static routing to the gateways.
Both Tunnel IP Addresses are multiple router hops away from the S-Series. The Primary Switch always uses the primary connection unless the Cloud Tunnel IP is not reachable, but The primary router does not backup the secondary router.

The primary has a static route with a probe pointing at the server subnet and using the cloud interface even though it is not a local next -hop by using recursive routing the router will forward the traffic as long as it has a route to the next-hop address.

The secondary router has a static route pointing at the server farm subnet and using the backup Cloud Tunnil IP address as a next hop. If the primary Tunnil IP stops replying to ping the probe fails, and the route is removed from the route table causing the route redistributed by the secondary router into OSPF to be populated in the route table.

The primary router does not redistribute the static and does not have a static route for the secondary tunnel which is used only when the primary tunnel is not responding to ping.
When there is no failure the Primary router will use the static route to reach the server subnet hosted in the cloud because OSPF has a higher administrative distance than a static route.
Server Subnet 192.168.52.0/24
Primary Tunnel IP Address 192.168.53.1
Secondary Tunnel IP Address 198.51.100.2
Primary default gateway 203.0.113.253
Backup default gateway 198.51.100.2
192.168.17.0 subnet between the routers
Environment
  • S-Series
  • Firmware 8.1.2.0 or higher
Procedure
Primary Router
1. Configure a probe named r52, to fail after two missed pings in five seconds and recover if less than two failed pings in five seconds.
probe r52 icmp
faildetect count 2 interval 5
passdetect count 2 interval 5
inservice
exit


2. configure a static route for the server farm subnet using the tunnel address as a next hop and tie it to the probe ( the recursive option is added automatically and does not need to be typed.
ip route 192.168.52.0/24 192.168.53.1 recursive 1 probe r52

3. Configure a static route to get to the subnet of the primary Tunnel IP address.
ip route 192.168.53.0/24 203.0.113.253 interface vlan.0.20 1


Backup router config
1. Configure static route to server farm subnet
ip route 192.168.52.0/24 198.51.100.2 interface vlan.0.51 1

2. redistribute into OSPF, the static route pointing at server subnet in the cloud
router ospf 1
router-id 1.1.1.1
network 192.168.17.0 0.0.0.255 area 0.0.0.0
redistribute static
log-adjacency
exit

!
Additional notes

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