100mb SFP Module in Gigabit Cisco 3850

[lccairns69489]

Hi, 

I'm trying to simplify my network cabinet of historical works. The hardware is involved 

Contemporary Controls Copper/Fibre switch - EISK8-100T/FC (lets say SW1 and SW2) 

Cisco Catalyst C3850 12port fibre, with secondary copper rack. (call it SW3)

Currently setup is

SW1>fibre>SW2>copper>SW3

I would like to remove SW2 and go straight into SW3 to remove junk from my cabinet. so it would be SW1>fibre>SW3

Everything is MM, Full-duplex

I believe the issue as due to the speeds, SW1/2 is 10/100Base, and SW3 is Gigabit ports. 

I have found a 100mb SFP module lying around but cannot for the life of me get the cisco switch to recognise the 100mb speed. 

GigabitEthernet1/0/8

Full-duplex, 1000Mb/s, link type is auto, media type is DWDM-3819 SFP

the Module is

Westermo 1100-013 1/3

Multimode/155mbps/1310nm

So the I think the questions are

- what SFP module so I need?

- Do I need to configure it or does it recognise the SFP module automatically?

- Or  do I need to upgrade SW1 to 1000mb aswell? 

I have tried to config both 7 an 8 as below, setting the port to negotiate on 7 with no luck

Thanks 

Core.2#show interface giga1/0/8
GigabitEthernet1/0/8 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is 0c11.6731.9408 (bia 0c11.6731.9408)
Description: DISABLED
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 1000Mb/s, link type is auto, media type is DWDM-3819 SFP
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)

interface GigabitEthernet1/0/7
description Wannac 4
switchport access vlan 15
switchport mode access
macro description Disabled-Port | Disabled-Port
spanning-tree portfast
spanning-tree bpduguard enable
!
interface GigabitEthernet1/0/8
description DISABLED
switchport access vlan 15
switchport mode access
switchport nonegotiate
macro description Disabled-Port
spanning-tree portfast
spanning-tree bpduguard enable
!

[kubn2]

Hi,

This really depends on the SFP modules that you have, some modules like 100/1000BASE-LX SFP support 2 speeds however most popular SFPs are single speed only, you can try setting speed on the gigabit interface to 100Mb/s and try then but again it might not be supported.

[Marvin Rhoads]

The DWDM-3819 SFP is a 1 Gbps-only transceiver that requires single mode fiber and a matching same-wavelength transceiver at the other end. While compatible with your 12-fiber-port Catalyst 3850, it is not a general purpose transceiver that's interoperable with just any other 1 Gbps transceiver. It is specialized for use with systems where your upstream device is using Dense Wave Division Multiplexing (DWDM) for transport. It can also only operate at 1 Gbps. To operate at 100 Mbps, you would need something like a GLC-GE-100FX at the Catalyst end.

Here are the references I used to answer your question:

https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/dwdm-transceiver-modules/datasheet-c78-382891.html

https://tmgmatrix.cisco.com/?npf=112