Is a 10gig mm fiber connection backwards compatable to a 1gig mm fiber?

[keithsauer507]

I have a trunk that is partially getting consolidated and upgraded.  I only have the parts to upgrade half of the connection at this point.  Currently its two 1gbps SFP Fiber optic mm 850nm optics.

Can I upgrade the one side with two 10gbps SFP+ fiber optic mm 850nm optics since I have this gear now, and the link would just work at 1gbps because the other side is 1 gig?

[chrihussey · Accepted solution]

No, the optics need to be the same on either side. They use the same wavelength, but need to operate at the same data rate.

Hope this helps.

[keithsauer507]

Ok thank you.

The issue is that I have an oppurtune time coming up where I can take a floor out of service and exchange two 4 SFP trays in 3750x switches with the NM-10G module, which has 2 SFP+ ports, and 2 regular SFP ports.

Perhaps I will load the existing 1 gig sfp's in the first slot on each switch, and then load the 10 gig sfp's in the last slot (4) Te2 on each switch. 

Then in a month when the core is swapped out in the data room (which will have 10 gig optics), we just have to run up to that floor and move the patch cables.

[chrihussey]

Sounds like a plan. If you have available fiber you could also have the 10G uplinks patched to the core location and just move the jumpers there. Either way will work.

[keithsauer507]

I don't have available fiber.  But I think I ran into another problem.

Upon closer inspection of the fiber cable that was put into the building years ago...  The outside jacket says 62.5/125 multimode.  I subtracted the foot marking on this third floor switch closet end and the foot marking on the first floor data center end and I get a difference of 146 ft.  That's 44.5 meters of OM1 cable.  To my understanding 10 gig is only certified up to 33 meters on OM1 cable.

I guess I can try it out, but if it doesn't link up then I can't blame the optics or the switches.  I'll have to keep that link at two * 1 gbps links.

[chrihussey]

Well it is a good thing you have done your home work. I'll bet you get link, it will just be prone to errors and I wouldn't want to rely on it.

If you absolutely want 10G you could look into the SFP-10G-LRM and would possibly also need mode conditioning patchcords. But if the Gig is sufficient that will probably be easiest and best.

http://www.andovercg.com/datasheets/cisco-sfp-10Gigabit.pdf

[keithsauer507]

Ok well I did some testing this morning.

I created a new vlan 777 in the datacenter switch, and a vlan 777 in this third floor switch stack.

I put Te3/1/1 on vlan 777 and also I picked a port, Gi3/0/2 in this case on vlan 777.

In the first floor I put Te7/1/2 in vlan 777 and also a port Gi8/0/2 in vlan 777.

I put a laptop off of each gigabit ethernet port, manually IP'd and did some SMB transfers from both machines.  Both laptops have SSD drives.  Although they are limited by the 1gig port, they appear to have very respectable throughput (upwards of 76MB/sec for big files, in the 30MB/sec for smaller files), and the one laptop is a Sony VAIO that is over 5 years old.

I'm not seeing any errors at all.  Maybe we are good after all.

3rd floor

TenGigabitEthernet3/1/1 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is f872.ea93.a6b5 (bia f872.ea93.a6b5)
MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 10Gb/s, link type is auto, media type is SFP-10GBase-SR
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:40, output 00:00:33, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 1496000 bits/sec, 780 packets/sec
5 minute output rate 47307000 bits/sec, 4354 packets/sec
371902 packets input, 86799628 bytes, 0 no buffer
Received 1822 broadcasts (1188 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 1188 multicast, 0 pause input
0 input packets with dribble condition detected
2449145 packets output, 3400103626 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

1st floor

TenGigabitEthernet7/1/2 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is f872.ea96.7eb6 (bia f872.ea96.7eb6)
MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 10Gb/s, link type is auto, media type is SFP-10GBase-SR
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:49, output 00:00:56, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 45345000 bits/sec, 4176 packets/sec
5 minute output rate 1457000 bits/sec, 752 packets/sec
2459791 packets input, 3411557052 bytes, 0 no buffer
Received 1475 broadcasts (905 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 905 multicast, 0 pause input
0 input packets with dribble condition detected
376253 packets output, 88227750 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out

Maybe I should add this interface to the port channel on both ends and have 11000 mbps

[chrihussey]

Thanks for the update. You'll probably be OK then. The specs are just what they are and not hard and fast rules. Just keep this in mind once fully in production. You could have instances where it works fine for a period of time and then flakes out or has intermittent errors. You'll know where to look first if that is the case.