SFP Issue

[Adjara Group]

Hello,

We have 3 old cisco WS-C3750X-24S-E - in stack, also in every switch we have inserted C3KX-NM-10G module.

This C3KX-NM-10G module has G1, G2/Te1, G3, G4/Te2 Ports. 

I have inserted 10G sfp to the G2/Te1, G4/Te2 ports in the first switch module and they works good. But when I try inset 1Gb copper sfp (brand is cisco) to the G1 or G3 ports - it shored as a "Not Presented".

In second switch module there is no any 10G sfp inserted and when I insert 1Gb copper sfp to this switch it showed and works correctly. 

How I can use in this C3KX-NM-10G module 10Gb sfp and 1Gb sfp simultaneous? 

[Jan Rolny · Accepted solution]

Hi Adjara,

I think you can use 10G and 1G together just in some combinations. Its described in Module documentation. 

C3KX-NM-10G (Figure 2)

The module has four slots. Two slots support only 1-Gigabit SFP modules. Two slots support either 1-Gigabit SFP or 10-Gigabit SFP+ modules. Note  The GLC-T SFP is not supported on the SFP+ slots of C3KX-NM-10G. The four slots are grouped as two pairs, with each pair consisting of one SFP slot and one SFP+ slot. Each pair supports either two 1-Gigabit SFP modules or one 10-Gigabit SFP+ module. A 10-Gigabit SFP+ module cannot operate at the same time as the corresponding 1-Gigabit SFP module in the pair. Supported combinations of SFP and SFP+ modules: Slots 1, 2, 3, and 4 with 1-Gigabit SFP modules Slots 1 and 2 with 1-Gigabit SFP modules and Slot 4 with one 10-Gigabit SFP+ module Slot 2 with one 10-Gigabit SFP+ module and Slots 3 and 4 with 1-Gigabit SFP modules Slot 2 and Slot 4 each with 10-Gigabit SFP+ modules A 10-Gigabit SFP+ module takes precedence over a 1-Gigabit SFP module except when an SFP module is first inserted in Slot 1 and has link. When you insert an SFP+ module in Slot 2, the SFP in Slot 1 retains link. The SFP+ module in Slot 2 does not operate. When the SFP module in Slot 1 is shutdown, loses link, or is removed, the SFP+ module in Slot 2 turns on. The SFP module in Slot 1 does not work as long as an SFP+ module is in Slot 2, whether it has link up or not. The same precedence applies to Slots 3 and 4.

You can check it here 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/hardware/install/notes/net_mod_note.html#wp129397

Best regards,

Jan

[Adjara Group]

"The GLC-T SFP is not supported on the SFP+ slots of C3KX-NM-10G" - strange, I have inserted 10G copper SFP (GLC-T) and it works...

[Ramblin Tech]

' "The GLC-T SFP is not supported on the SFP+ slots of C3KX-NM-10G" - strange, I have inserted 10G copper SFP (GLC-T) and it works...'

FWIW... In Cisco-speak, "not supported" means TAC will not work on the issue, most likely because Engineering did not dev-test the function. It does not mean that the function does not actually work.

[Joseph W. Doherty]

Also, sometimes support is added in later IOS releases, which should be documented in release notes not original documentation.

Also, also, I believe later IOS releases might now allow unsupported transceivers to work, without having to use earlier hidden configuration commands.  But as Jim notes, if unsupported, TAC will not work on issues if they are being used.

BTW, I believe I've noticed the copper SFPs seems to be often unsupported on later series switches.  My guess would be, with copper gig ports being so common, as would be the case for a 3750X, Cisco doesn't want to support them on such switches.

[Joseph W. Doherty · Accepted solution]

"How I can use in this C3KX-NM-10G module 10Gb sfp and 1Gb sfp simultaneous?"

You can only use two of the four ports, and only either one port of each gig/10g pair.  So, you can have one gig and one 10g, or two gig or two 10g.

@Jan Rolny 's reply has the details.

If it helps any, think of each pair of gig/10g ports as a single SPF+ port.

[Adjara Group]

Thanks for your reply,

Looks like I cant use  this combination 1gb SFP (G1 Port), 10gb SFP (G2/Te1 port), 1gb SFP(G3 port), 10 gb SFP (G4/Te2)? 

[Reza Sharifi]

Correct. Ports 1 and 3 are 1Gig (SFP) and ports 2 and 4 are 10Gig (SFP+).

HTH

[Joseph W. Doherty]

"Correct. Ports 1 and 3 are 1Gig (SFP) and ports 2 and 4 are 10Gig (SFP+)."

I thought SPF+ ports support gig or 10g, but ports 2 and 4 are only 10g SFP.(?)

Otherwise if module only can support 2 active 10g ports, you would only need two SFP+ ports to provide like gig/10g combos.

BTW, this module's approach isn't new.  I recall some switches providing a pair of RJ45 uplink ports, one MDI and the other MDI-X (only one of the pair could be used).  Or, when copper FE first came on the scene, I recall some switches having, again, a pair RJ45 uplink ports (only one at a time could be used), one Ethernet the other FE, but for later switches there was a single dual speed 10/100 port.

[Joseph W. Doherty]

Correct.