> Source: [sk184536](https://support.checkpoint.com/results/sk/sk184536)

# sk184536 - After upgrading Security Gateways (1600 Series) with CPAC-2-100/25F line cards to R81.10 or R81.20, some interfaces fail to establish a physical link

| Property | Value |
|----------|-------|
| Solution ID | sk184536 |
| Date Created | 2026-01-29 |
| Last Modified | 2026-02-04 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R81.20, R81.10 (EOS) |
| Platform | 16000 |

## Symptoms

- * After upgrading Quantum Security Gateways (CP16200) with CPAC-2-100/25F line cards to R81.10 or R81.20, some interfaces fail to establish a physical link.

* The affected interfaces:

  * Appear `UP` in the WebUI
  * Report auto-negotiation as enabled when checked with ethtool
  * Show `link-state link up` in the CLI output
* Example output of the `show interface` command:

  `
  clish> show interface eth1-01
  `  
  `
  state on
  `  
  `
  mac-addr `   
  type ethernet   
  link-state link up   
  mtu 1500   
  auto-negotiation Not configured   
  speed 25G   
  ipv6-autoconfig Not configured   
  monitor-mode Not configured   
  duplex full   
  link-speed 25G/full   
  comments {plalfm23313 eth1/2}   
  ipv4-address Not Configured   
  ipv6-address Not Configured   
  ipv6-local-link-address Not Configured

## Cause

The issue occurs because of legacy interface configurations inherited from deployments originally installed on R80.40.

In these configurations, some interfaces were configured with a fixed link speed (for example, `link-speed 25G/full`) instead of using auto-negotiation.

Example configuration observed on affected systems:

`set interface eth1-01 link-speed 25G/full`  
`set interface eth1-01 state on`  
`set interface eth1-02 link-speed 25G/full`  
`set interface eth1-02 state on`  
`set interface eth2-01 auto-negotiation on`  
`set interface eth2-01 state on`

<br />

## Solution

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