# Bug: When select Speed other than default to 2.5Gbps

**URL:** <https://forum.alta.inc/t/bug-when-select-speed-other-than-default-to-2-5gbps/4197>\
**Category:** Routers\
**Created:** [January 7, 2025, 12:54pm UTC](https://forum.alta.inc/t/bug-when-select-speed-other-than-default-to-2-5gbps/4197 "2025-01-07T12:54:17Z")\
**Posts on this page:** 1\
**Showing post:** 10

<div class="post-metadata">

**Author:** ![Hefty](https://forum.alta.inc/letter_avatar_proxy/v4/letter/h/ed655f/32.png) [@Hefty](https://forum.alta.inc/u/Hefty)\
**Post date:** [January 17, 2025, 11:42am UTC](https://forum.alta.inc/t/bug-when-select-speed-other-than-default-to-2-5gbps/4197/10 "2025-01-17T11:42:05Z")

</div>

I can confirm I have the same issue, not that I need to force it, just thought I’d test.

Interface negotiates fine @ 2.5gbps, however if I try and force it drops and won’t come back.

With “Default” set…

```auto
        Supported ports: [TP AUI BNC MII]
        Supported link modes: 10baseT/Full 
                                100baseT/Full 
                                1000baseT/Full 
                                2500baseT/Full 
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes: 10baseT/Full 
                                100baseT/Full 
                                1000baseT/Full 
                                2500baseT/Full 
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes: 10baseT/Half 10baseT/Full 
                                             100baseT/Half 100baseT/Full 
                                             1000baseT/Full 
                                             2500baseT/Full 
        Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 2500Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 2
        Transceiver: external
        Auto-negotiation: on
        Link detected: yes

```

When forcing to 2.5gbps…

```auto
        Supported ports: [TP AUI BNC MII]
        Supported link modes: 10baseT/Full 
                                100baseT/Full 
                                1000baseT/Full 
                                2500baseT/Full 
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes: Not reported
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Link partner advertised link modes: 10baseT/Half 10baseT/Full 
                                             100baseT/Half 100baseT/Full 
                                             1000baseT/Full 
                                             2500baseT/Full 
        Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
        Link partner advertised FEC modes: Not reported
        Speed: 2500Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 2
        Transceiver: external
        Auto-negotiation: on
        Link detected: no

```

I tried adding in just 2.5Gbps as an advertised link mode again using

`ethtool -s eth1 advertise 0x800000000000`

Still no joy, going back to “Default” in control brings it back up fine.

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_[View the full topic](https://forum.alta.inc/t/bug-when-select-speed-other-than-default-to-2-5gbps/4197)._