SFP speed in MS225

[jphipps]

We are replacing some Cisco 2960's with Meraki MS225's. These connect up to our core switches, Cisco 3750-X's, through a Cisco SFP-10G-SR that worked fine when they were in the 2960's.

The MS225's are configured, updated, and ready to go. I put the SFP into the Meraki and while it shows connected and auto-negotiate it never connects up to the 3750. It appears that the 3750 is hard-set to 10000 speed and Full Duplex, no auto-negotiation option and while that port is enabled and working when connected to the 2960 the 3750 SFP link light shows disabled when connected to the MS225.

I've looked to hard-set the speed and duplex on the MS225 but the only options are Auto, 1G auto and 1G forced. There are no 10G options to set. Why would there be no 10G options under Link Negotiation?

[MarcP]

Seems to be normal, never looked into it till now.

when you select the port, whats written in the status segment?

Maybe the SFP from the cisco classic switch is not compatible to the Meraki? So you only can use 1G?

Did you try to set your Core to auto/auto as well? Even though it should work with auto auto on Meraki side.

[jphipps]

Thanks for the quick responses.

Yes, the MS225's are in a stack. Three MS225-48-FP all connected with stacking cables. Currently, I have one ethernet cable connected to the core for internet connectivity but if I unplug that there is no internet connection for these devices. The SFP is in port 49 of one of the switches and I have tried the SFP port on another of the MS225's.

The SFP module shows as a Cisco SFP device at 10.3 Gbps so that appears to be correct.
On the core, it appears that it is hard-set Full Duplex and I found a Cisco support page that said that 10G ports do not support speed or duplex features and only operate at 10,000Mb/s and in full-duplex mode.

[cmr]

@jphipps we have MS225s links to Cisco 3850s via 10GbE transceivers in port 49, though we are using the Meraki ones:

Are the ports both side set to trunk mode native VLAN1 allow all VLANs (or at least matching)?  Have you got any port channels configured on the 3750-Xs?

Finally, I am sure you are aware, but just in case, the 3750-Xs are EOL in 6 months time as far as I know.

[jphipps]

@cmrWe are using a Cisco branded SFP and I did find it as a Meraki supported SFP.

It appears that both sides are set to trunk mode and VLAN1 with all VLANs allowed.

While I do some networking I'm more of a generalist since I have to support many different things and normally call in an expert once it goes above my head or I can't find any answer online. That being said I can't say for sure but I just pulled this from the config if that will help answer this question.

interface TenGigabitEthernet5/1/1
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 3 mode active

As for EOL, yeah, these MS225s are replacing the 2960's that were EOL last year and once we get these going we replace the 3750's next year.

Thanks for your help.

[GIdenJoe]

Hmm are you sure both ends use the same SFP kind?
Most SFP's are NOT multi speed, so usually a 10G SFP cannot transmit 1G.  Yes there are exceptions but the standard SFP's are not that 🙂

SFP's adhering to the same standard like 10G SR should linkup just fine independent of the brand used.

Only some DAC cables of other vendors can give trouble on some devices (usually not Meraki).

So there is no link negotiation on these SFP's.

Are you sure the MS225 is detecting the 10G-SR SFP correctly?

Also are you sure you're not using a stackmember that is an MS210 instead of an MS225 to uplink?

[jphipps]

@GIdenJoe  I haven't looked specifically at the SFP in the 3750 but I'm pretty sure all of these SFP were Cisco branded 10G SFPs. Researching this I did find where I could not set the speed or duplex for the SFP which is why I found it strange that the Meraki gave the 1G options.

When we had this core (3750's) and these 2960's installed a couple of years ago it was an all Cisco install and if I plug this SFP back into the 2960 I'm replacing it comes back online but when I put it in the Meraki, the Meraki shows it connected but the 3750 shows it as disconnected or actually "line protocol is down (suspended)".

It's possible that there is a setting on the 3750 port that's causing this but according to the MSP we got these from, they went through the configs and said everything seemed ok.

I checked the MS225 that the SFP is plugged into and it is showing as a 10.3 Gbps Cisco SFP-10G-SR and all three switches of the stack are MS225's.

Thanks for your help.

[cmr]

@jphipps this line, channel-group 3 mode active, means that the port is part of an etherchannel (or port channel).  I'm guessing you have one cable from the 3750X to the MS225, if so you don't want that line.  However before removing it look at the part of the Cisco config for the channel-group.  There might be a different mode there or different VLANs in the trunk etc. which can stop it coming up.

[jphipps]

@cmrThere is an entry for the channel group 3, I'll put it below but it looks to be the same as the actual port.

interface Port-channel3
description PortChannel to Mezz Switches
switchport trunk encapsulation dot1q
switchport mode trunk

As far as cables, the local tech wanted to hook this stack up to the core and put a couple of cables over from the 2960 into the stack to test and make sure everything was ok before we completely removed the (4) 2960's. When I first hooked everything up I got the MS225's in the stack, put one ethernet cable from the core in to get the stack on the internet and upgraded the firmware and did all the setup. I then pulled the SFP from one of the 2960's that I freed up and was going to get that connection as the main link between the core and MS225's then one that communication was working I was going to start moving a handful of workstations over to the MS225 and make sure all was well there.

When you say "you don't want that line" are you taking about the SFP connection or the ethernet back to the other Cisco switches?

Thanks for your help.

[cmr]

@jphipps I was referring to the channel-mode line, if you only have one link from the 3750Xs to the MS225s then this is redundant and *could* be causing an issue.

[jphipps]

@cmr  My apologies but I'm not clear (my lack of knowledge) on why we would not have the 3750 stack and the MS225 stack connected. Currently, the 3750 stack and the 2960 stack are connected with fiber links through these SFP's. My understanding was this was for redundant connections between the stacks and faster links for any traffic between the stacks.

Would the MS225 stack not also be connected the same way to the 3750 stack?

Thanks

[cmr · Accepted solution]

@jphipps are you intending on connecting the 3750X stack to the MS225 stack with two links bonded together?

If so then leave the config line there and connect both fibres, if not and you are only going to use a single connection then you don't need the port-channel config on the 3750X side.

I am not saying that they should not be connected, just trying to clarify how many connections there will be between the stacks.

Out of interest, you haven't taken one cable from the 2960 stack and moved it to the 225s have you, leaving the other one still plugged into the 2960s?  If so that is the issue as both cables from a port-channel pair must be plugged into the same stack at each end, i.e. both in the 3750Xs <-> both in the 2960s OR both in the 3750Xs <-> both in the MS225s 

[jphipps]

@cmrThat's exactly what is going on! I ran this the other day when researching this and now it makes sense.

Number of channel-groups in use: 3
Number of aggregators: 3

Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
1 Po1(SU) LACP Te1/1/1(P) Te2/1/1(P)
3 Po3(SU) LACP Te3/1/1(P) Te5/1/1(P)
4 Po4(SU) LACP Te3/1/2(P) Te4/1/2(P)

Channel 3 is two links coming down from the 3750's to two of the 2960's in their own stack.

So it sounds like as long as I get both SFP's from the existing 2960 stacks moved down to the MS225 then the SFP's on the 3750's will enable and allow that traffic.

Thanks so much for the help!

[cmr]

@jphipps you'll also need to make sure the two ports on the 225 stack are aggregated:

[jphipps]

This is great @cmr thanks again.

I'll get these aggregated for the two EtherChannels (two pairs or two) coming down from the 3750 and we should be good to go.

[MarcP]

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@jphipps wrote:

@GIdenJoe  I haven't looked specifically at the SFP in the 3750

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"sh inv" and you can check the SFP through CLI

[jphipps]

Thanks for the info. It appears to be the same model number as the one that I moved from to 2960 to MS225, SFP-10GBase-SR.