This article contains information related to the error "Invalid JSON format" when we use loopback interface for Juniper secure connect

When using the Juniper secure connect with the Lo0 interface, user may encounter an "Invalid JSON format" error on JSC client.

When using the JSC with the Lo0 interface and having only the loopback interface in the "system services web-management interface," user may encounter an "Invalid JSON format" error when accessing the JSC.

To make it work you will need to remove the loopback interface from all the VPN JSC configuration and an external interface must be added instead

Please apply the same under "system services web-management interface." Remove the Lo0 interface and add an External Interface.

However, if user add the external interface to "system services web-management interface," the JWEB will be accessible via the external interface as well. To prevent JWEB from being accessible via the external interface, ensure that the configuration for “security zones security-zone test interfaces <external interface> host-inbound-traffic system-services” does not include HTTPS. This means that “host-inbound-traffic system-services https” should be disabled for the external interface.

If you follow the above, then your JSC will work, and JWeb will also work with the external interface (which cannot be stopped even by deleting “web-management management-url”). 

However there are some cases where the SRX will work with External and Loopback interfaces configured under "system services web-management https"

Example config:-
Assume reth0.0 is external interface,

[edit system services web-management https]
+     interface [ reth0.0 lo0.0 ];
[edit security zones security-zone Untrust interfaces reth0.0]
+      host-inbound-traffic {
+          system-services {
+              ike;
+              ping;
+              tcp-encap;
+              ssh;
+          }
+      }
[edit security zones security-zone Untrust interfaces lo0.0]
+      host-inbound-traffic {
+          system-services {
+              https;
+              ike;
+              ping;
+              tcp-encap;
+              ssh;
+          }
+      }

2024-11-02 : Article Created

2026-05-18: Modified product categories.