topic Re: ICX 7450 won't pass traffic to a Mellanox SN3420M in ICX Switches

ICX 7450 won't pass traffic to a Mellanox SN3420M

abedard_wolf — Sun, 09 Nov 2025 00:00:10 GMT

Installing a pair of new Mellanox SN3420M switches

Cross connecting them to an existing stack of ICX 7450 using an LACP etherchannel of 2x 10gb fiber links

Etherchannel comes up, but won't pass any traffic.

Ruckus T1 + nvidia support confirm the configuration is correct, VLAN settings are the same on both sides, LAG group comes up active/active, packets are flowing but can't get any VLAN traffic over the link.

Tried a single non-etherchannel link, same issue.

Anyone run into this before?

Can anyone confirm if there's a firmware upgrade to fix this before we call another weekend outage?

Re: ICX 7450 won't pass traffic to a Mellanox SN3420M

Chandini — Tue, 11 Nov 2025 10:19:29 GMT

Hi Abedard_wolf

Thank you for reaching us

Below is what I understand about the issue

Mellanox SN3420M switches cross-connected to a RUCKUS ICX 7450 stack via LACP EtherChannel (2×10Gb fiber).
The LAG comes up active/active, VLANs match, and packets flow — but no VLAN traffic passes.
Even a single non-LAG link shows the same behavior.

Could you verify the below setting on both sides

Verify VLAN tagging:
- On ICX: Use "show vlan br <eth/lag> <port number>" to confirm VLANs are tagged/ untagged correctly on the LAG.
- On Mellanox: Confirm VLANs are tagged/untagged with same config.
Test with native VLAN only:
- Temporarily remove all tagged VLANs and test with a single untagged VLAN to isolate the issue.

Thank you

Re: ICX 7450 won't pass traffic to a Mellanox SN3420M

abedard_wolf — Mon, 17 Nov 2025 15:29:51 GMT

VLAN tagging on both sides is identical

Attempted a single cable with a single untagged VLAN on both sides and it still won't pass traffic.

Port counters for sent and received packets increments on both sides, but all frames seem to be dropped.

Spanning tree is not blocking the port.

Re: ICX 7450 won't pass traffic to a Mellanox SN3420M

Chandini — Thu, 20 Nov 2025 14:56:48 GMT

Hi Abedard_wolf

Thank you for reaching us

Is the single link configured as a non-LAG link meaning does not have any LAG configuration and is the issue still seen ?

Thank you

Re: ICX 7450 won't pass traffic to a Mellanox SN3420M

abedard_wolf — Thu, 20 Nov 2025 16:23:18 GMT

Yes, correct

We fixed the issue last night. The issue was that Spanning-tree was enabled on the Brocade but was off on the Mellanox. Once it was enabled on the Mellanox traffic started to flow.

This despite the ports showing as 'forwarding' in Spanning-tree and all interfaces being up/up