> Source: [sk183529](https://support.checkpoint.com/results/sk/sk183529)

# sk183529 - Traffic that relies on the IS-IS protocol is interrupted or does not pass

| Property | Value |
|----------|-------|
| Solution ID | sk183529 |
| Date Created | 2025-06-04 |
| Last Modified | 2025-06-05 |
| Technical Level | Advanced |
| Products | Security Gateway, Scalable Platforms |
| Versions | R82.10, R82, R81.20, R81.10 (EOS), R81 (EOS), R82.10, R82, R81.20, R81.10 (EOS), R81 (EOS) |
| OS | Gaia |

## Symptoms

- * Traffic that relies on the IS-IS protocol is interrupted or does not pass.

* The `/var/log/routed.log` file on the Security Gateway contains this line:

  `ERROR: isis_interface_parse_config(<X>): IS-IS currently only supports interfaces with an interface index less than or equal to 255. Configured logical <Name of Interface> has index <Number Greater than 255>. Cannot run IS-IS on this logical interface.`
* The `/var/log/dump/usermode/` directory on the Security Gateway contains core dump files for the "`routed`" process.

## Cause

By design, the IS-IS protocol supports interfaces only with a Linux kernel index value of less than or equal to 255.

To see the Linux kernel index values for interfaces, run: `fw ctl iflist`

## Solution

This solution requires authentication. Please log in to view the full solution.

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