SFP Card connectivity issue

[santosh kumar]

Hi,

I have cisco ASR 1002 X router with 1000Base SX SFP MMF and

          Cisco 3850  switch with 10GBase SR SFP+ MMF

Now, I want to connect router to switch with the use of this modules. when I connect I am unable to see link status up.

what are the possibilities to make the connectivity up.

Need some suggestion.

Regards,
Santosh

[Matt Delony]

Hello santosh kumar,

Please try using same optic on both sides of link. Either both 1000Base-SX. Or both 10Gbase-SR.

Using different speed optics on both sides of link would not allow for link up in this situation.

[santosh kumar]

Let me try this.

[Sumant Mali]

Santosh Kumar,

Try to use same speed and same type SFP on each side. On 3850 you seem to have used 10G SFP. If you are bringing up 1G connection with ASR1002-X built-in interfaces, please use 1G SFP on either side.

Thank you,
Sumant

[santosh kumar]

Hi Summant,

I connected 1000Base SX SPF MMF card on both cisco ASR 1002 x and Cisco 3850 switch. But still, ports are showing down.

Also, it's observed that at the switch end its showing as not connected.

I changed speed 1000 but no luck.

Regards,

Santosh

[Sumant Mali]

Please see if following helps:
- Observe syslogs on both ends when you enable interfaces using 'no shut' CLI.
- If transceiver are not showing any error pointing towards unsupported Transceiver or so, we should be good from SFP point of view.
- See if the 'link' is down or 'line protocol' is down on either side. (assuming cable is not at fault).

Share exact SFP PIDs from 'show inventory' and current running configuration for Gig interfaces on either side if you still see the issue.

Cheers,
Sumant

[santosh kumar]

Hi Sumanth,

I connected the same kind of modules at cisco 1002x and cisco 3850 switch (its has 1gig and 10gig support) but link isnot coming up.
At switch end, it is down down (not connected) and media type is not showing anything. On router end its good.

I also tested by connected cisco 1002x to my other switch 4958 its working good.
I am not understanding in cisco 3850 whether I need to configure anything.
I am using the same kind of modules at both sides.

Regards,
Santosh

[Sumant Mali]

Hi Santosh,

When you 'no shut' interfaces on both sides, what exact logs do you see for interface bring up? Please enable console logging and share syslogs from both sides while interface bring up. Need to know what is the configuration on both side as well. 

When you are saying 3850 side shows 'down/down' that means it is not even receiving any signal- link is down. But at same time the ASR1K side if showing as 'up/up' per your confirmation, it doesn't seem logical. See if there is negotiation disabled on ASR1k side (assuming this is Copper connection you are trying?) Else, this would not be the case. 

More details on logs would help. Also, try using same cable you used on working connection if possible to rule out cable issue.

Additional things that you can try:

- Connect both SFPs on two interfaces on ASR1K side only (loop on same spa 2 interfaces, e.g. Gi0/0/0 --- Gi0/0/1). And check if link comes up properly on both interfaces.

- Try above same test by using the same SFPs on 3850 side on two interfaces there. See if the external cable loop brings back the links on 3850 side. 

This way you can isolate which side configuration has problem. And in all of the tests listed, syslogs are the key thing to observe. They will hint you towards root cause. 

Good luck! 

Cheers,

Sumant

[santosh kumar]

Hi Sumanth,
My Observations :
1. Both sides showing down / down but on cisco 3850 its showing down/down not connected.
2. When i connect the same ports in other switch and cisco ASR 1002x its working fine.
3. I Tested with fiber meter and observed that when cisco 1 gig SFP connected to cisco 3850 the reading is zero. Also tried with Curvature 1gig SFP module same the reading is zero.
Whereas on cisco router the reading on the meter is good with both the fiber modules.
Anyway i will share sys logs for further troubleshooting.

I connected the SFP on the 2 cisco routers and tested they are working fine. I am facing issue only with Cisco 3850. When I connect 10gig module to cisco 3850 some power is showing whereas when i connect 1 gig module no power is showing.
I need to try looping in switch end but they are in production. Need to check.

[Matt Delony]

Hello santosh kumar,

Down/down (notconnect) usually indicates problem with physical layer.

Make sure of the following:

• Interfaces on both sides are admin up
• Interfaces support the optic that is being used
  • On 3850 it may have expansion module on the right side that is used for plugging in SFP. If you're using this, make sure the port you're using supports the optic. It should have small letters above each port indicating supported speed
• Make sure you're using proper cable. This is multi-mode optic, so you should be using multi-mode cable
• Make sure that transmit and receive strands are connected properly. Sometimes they could be reversed and it could cause link to stay down.
• If there is patch panel in use, make sure that the patching has been connected to the right devices.

[Giuseppe Larosa]

Hello Santosh,

as explained by other colleagues optics SFP have no speed negotiation capabilities as we can see on a RJ-45 connection.

so a 1 Gbps SFP is not compatible with a 10 Gbps SFP+ and the second one is not able to fall back to 1 Gbps speed.

Physical layer is different , different modulation schemas are used for 1 Gbps over fiber and for 10 Gbps over fiber.

So even if the two SFPs may be working at the same wavelength they are not able to inter-operate.

The C3850 port may be able to support both SFP or SFP+ so you just need to put a matching SFP on the C3850 to achieve a working link.

Hope to help

Giuseppe

[paul driver]

Hello

The interoperability between these two sfp's wont work, as suggested try using the same optical speed sfps for a successful connection