Adding a less preffered default route?

Routers
1

I have a WAN which is learning a default route via BGP. All good

I want to add a secondary static route for 0.0.0.0/0 pointing to an IP on the inside of the device as a secondary backup route should BGP go down. Basically a higher cost default route

If I try to create a static route with 0.0.0.0/0 as the destination I get an error “**Please enter a valid IP and subnet size”
**
How do I simply create a less preffered static default route? thanks

2

I wonder if you could create two routes (each for half the internet) to accomplish the same goal, using 0.0.0.0/1 and 128.0.0.0/1 and then give higher metric than the 0.0.0.0/0 route learned from BGP?

3

Unfortunately that wouldn’t work. ‘Specificity always wins’

Which means if you created two routes then they would always have preference over the default route regardless of cost.

4

Totally didn’t even think about that, good point!

I think you’ll have to do it via CLI then, as they don’t allow the 0.0.0.0/0 as a route option in the GUI.

5

The reason default routes are forbidden as static routes is how traffic ends up policy routed by mwan3 underneath. Each default route must have associated mwan3 configuration, which is always associated with a WAN interface. Even if you added a higher cost default route, traffic from clients would never follow it as they strictly get PBRed per the mwan3 config.

The way to achieve that is to make the network where your second default route resides into a WAN interface. That means it won’t act as a LAN (no DHCP/DHCPv6 server, no DNS for clients, etc.). There are other complications in LAN vs. WAN interface handling with Route10 and most all comparable products, like firewall and NAT config, potential problems from asymmetry on the return traffic, among other possible complications. Mixing LAN-type and WAN-type functionality is generally undesirable for those reasons.

Probably the best workaround, if Route10 needs to handle clients on the network where your second default is reachable, would be to create a separate interconnect network strictly used for reaching the internet. Set that up as a WAN interface with a higher metric than your BGP-obtained interface’s metric. Then mwan3 will handle failover when the preferred WAN fails. Could just be a /30 between Route10 and your other router.