> Source: [sk111053](https://support.checkpoint.com/results/sk/sk111053)

# sk111053 - "RTGRTG0019  OSPF: OSPF doesn't support interfaces enabled on multiple areas without at least one of the areas being the backbone" error when configuring an interface to use an OSPF area other than the OSPF backbone area

| Property | Value |
|----------|-------|
| Solution ID | sk111053 |
| Date Created | 2016-04-16 |
| Last Modified | 2023-08-15 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R81.20, R81.10 (EOS), R81 (EOS) |
| OS | Gaia |

## Symptoms

- * "`RTGRTG0019 OSPF: OSPF doesn't support interfaces enabled on multiple areas without at least one of the areas being the backbone`" error in Gaia Clish when configuring an additional interface to use an OSPF area other than the OSPF backbone area.

* "`At least one interface must be configured on the Backbone Area if more than one area is going to be used`" error in Gaia Portal when configuring an additional interface to use an OSPF area other than the OSPF backbone area.

* *Example*:

  1. OSPF is configured on Gaia OS with a single interface *eth1* that does not belong to the OSPF backbone area.

     `
     HostName> show configuration ospf`  
     `
     set ospf area backbone on`  
     `
     set ospf interface eth1 area 0.0.0.20 on`  
     `
     set ospf interface eth1 priority 1`  
     `
     set ospf area 0.0.0.51 on`  
     `
     set ospf area 0.0.0.20 on`  
     `
     `
  2. Trying to configure an additional interface *eth2* to use an OSPF area other than the OSPF backbone area fails:

     `HostName> set ospf interface eth2 area 0.0.0.51 on`  
     `
     RTGRTG0019 OSPF: OSPF doesn't support interfaces enabled on multiple areas without at least one of the areas being the backbone. Enable OSPF on an interface on the backbone or disable OSPF on other interfaces before repeating this action. You can review the ospf configuration with "show configuration ospf"`
  3. As a result, OSPF virtual link can not be configured, because Gaia OS is not an OSPF ABR.

## Cause

This behavior is by design.

ABR without the backbone is not supported (because it is not consistent with RFC 2328).

The current design allows the following configuration options:

* Either connect Security Gateway on Gaia OS directly to the OSPF backbone - in this case, Security Gateway can become an OSPF ABR.
* Or connect Security Gateway on Gaia OS only to a single OSPF area with no option to become an OSPF ABR.

## Solution

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