This is a very specific question - hopefully someone has tested this or run into this scenario...
I was trying to connect a Cisco 3845 router to a 100 Mbps circuit. Specifically, I was trying to connect this circuit to the on-board Gigabit Ethernet port (Gig 0/0). This is the port that can be used as either an RJ45 or SFP slot. The only SFP I had was a multi-mode 100 Mbps SFP. When I hooked it up to Gi0/0, I got a message saying the SFP type wasn't supported on the chassis.
I was able to deploy the 3845 and since then I haven't had the correct hardware to recreate the exact scenario. Has anyone experienced this? Is it simply because Gigabit interface on a 3845 won't support a Fast Ethernet (100 Mbps) SFP?
Not all SFP's will just plug in and work. Here are the SFP's that are considered compatible with the 3800 series ISR's.
GLC-LH-SM= Gigabit Ethernet SFP, LC connector, LX/LH transceiver
GLC-SX-MM= Gigabit Ethernet SFP, LC connector, SX transceiver
GLC-ZX-SM= 1000BASE-ZX SFP
CWDM-SFP-1470= Coarse wavelength-division multiplexing (CWDM) 1470-nm SFP Gigabit Ethernet and 1G/2G Fibre Channel (FC)
CWDM-SFP-1490= CWDM 1490-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1510= CWDM 1510-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1530= CWDM 1530-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1550= CWDM 1550-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1570= CWDM 1570-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1590= CWDM 1590-nm SFP Gigabit Ethernet and 1G/2G FC
CWDM-SFP-1610= CWDM 1610-nm SFP Gigabit Ethernet and 1G/2G FC
Hi, better late than never I suppose, we have had the same issue. Unfortunately your experience is correct, the 3845 will not support a 100Mbps SFP in the onboard G0/0 SFP slot. It is impossible.
2900/3900's can do this, but only with a the GLC-GE-100FX type SFP. No other SFP's will work in the onboard Gigabit slots while running 100Mbps.