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Forum Discussion
GSM7328FS / GSM7328S 10 gig ports
Our core switches are a stack consisting of a GSM7328FS and a GSM7328S.
The GSM7328FS is a blue v1, the GSM7328S a silver v2 (replacement for a v1 under the excellent lifetime warranty).
They are stacked via the rear module bays.
My query relates to the 10 gig ports. The blue GSM7328FS has AX743 (SFP+) modules in the front bays, and of course the silver GSM7328S has two 10 gig SFP+ ports.
I tried connecting both switches in turn to a 1 gig fibre switch with a DAC cable. The AX743 modules show a link light, the GSM7328S SFP+ ports do not.
In neither case do I get any connectivity. I read somewhere that the 10 gig ports can't negotiate down to 1 gig. Is this correct? Or is there another reason they won't connect?
We are updating our backend hosts and the aim is to connect them in at 10 gig to the core switches. Unfortunately we don't have any other 10 gig switches to test the connection with. Any advice much appreciated.
2 Replies
There are 2 things: Yes it is absolutely possible that SFP+ ports don't support SFP or 1GE. While many devices with SFP+ slots do work with slower 1G SFP modules it can happen that they do not. The AX743 module doesn't explicitely mention SFP support. Though I have used them in the past I have never used them with 1G fiber.
However I think there is a chance that one or both ends are not running in the same port mode. Usually these module ports and some 10G ports like on the GSM7328S can run in ethernet or stacking mode. You'll have to decide if you want /can stack them (I don't know if those 2 can be stacked) or simply use the 10G ports as regular ethernet-based uplink.
Check out the the CLI manual for both switches. They should have a "show stack-port" command where you can identify the port mode of all ports that can actually be run in either of both modes. I'm certain the module slots are configurable and most of these module slots on the GSM73xx series were defaulting to stacking mode.
You can switch them between ethernet and stacking mode, however a switch has to reboot in order to actually switch the port mode. (Still valid on the current M4300 switches).
Many thanks for the reply and sensible suggestions msi.
The ports were already in ethernet mode (this is also visible and configurable) through the browser based interface).
We have a Synology box with 10 gig cards and (lightbulb moment) with a bit of temporary re-configuration I was able to test connectivity to the 10 gig ports on the Netgear switches - and they work fine.
So I guess the problem was that the 10 gig modules can't talk to 1 gig. I hope this helps someone in the future (this is ports 25 and 26 on each switch, 27 and 28 being the rear module bays).
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