This article explains an issue where the default route pushed by MIST is not seen in the SRX routing table

On running "show route" command from the SRX CLI, default route pushed by MIST is not seen.

When a WAN link is configured on SRX from MIST portal, a default route pointing towards that interface gets pushed to the device, along-with RPM and IP-monitoring policies to monitor the link health. The target-address in the RPM policy is set to 8.8.8.8 by default. However, this default route pushed by MIST will not be seen in the routing table in case there is no reachability to internet via the respective WAN interface, as the RPM probes will fail and the device will disregard the default route pushed by MIST.