MX250 WAN port 100Mb Copper SFP

[dqsg22]

Short Version: Can the MX250 operate at 100mb/half-duplex with a copper SFP in the WAN port?

Long Version:

We ran into an issue recently installing a new MX250. We overlooked that the dedicated WAN ports are SFP only in this model, and as such did not have a Meraki SFP handy. We ordered one, but to get it working in the meantime we used a Cisco GLC-TE SFP. I've never had an issue using these with Meraki devices in the past, but we were unable to even get a link light using this.

I turned out the problem was the SFP would not auto-negotiate to 100Mb (The MX is plugged directly into the ISP, and through tests with another switch we observed the ISP router is 100Mb/half-duplex). The setting could not be changed to less than 1Gb in the hardware.

In order to actually make it work we were forced to insert a switch in between the MX and the ISP to basically act like a glorified media converter (still using the cisco SFP in the meraki). This switch cannot stay, and we hope to remove it when we get the Meraki SFP.

I will not be back at the remote branch where this was installed for some weeks, and I have some concerns about the MA-SFP-1GB-TX that we ordered. In the specs it lists it's operating speed as 1Gbps, where Cisco's GLC-TE actually lists it's speeds as 10/100/1000. I am worried that the problem is not with the SFP, but with the MX250 itself not being able to set it's WAN ports to less than 1Gbps. If this is the case we are hosed.

Can anyone confirm this?

Thank you

[BrandonS]

I think you can.  Log into the local web interface on the MX to check.  You should see something like:

[BrandonS]

I would get that router fixed or replaced though.  100-half is not cool.

[dqsg22]

It was provided by the ISP. From my experience it's fairly common with smaller branches.

[BrandonS]

You should know auto <> 100-Full is a no no. They might actually have hard coded 100-Full and you leaving the MX at Auto causes a mismatch: https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/17053-46.html#auto...

[dqsg22]

My only option to hard-code the speed were AUTO, 1Gbps SX, or 1Gbps LX.

[benny]

Hi dqsg22, 

We have rolled out 50 odd MX's into branches all with Ethernet handoff from our MPLS provider. I've always known on our 100M links that our provider hardcodes the link to 100 / FULL. We had a issue at one site whereby one MX had not been set with manual speed and duplex and the router had negotiated 100 / Half. 

Like others have pointed out it is critical that you either have Auto to Auto or Manual to Manual with matching settings on each end. 

[PhilipDAth]

To enable auto speed duplex/negotiation both sides of the link have to have it enabled.

If one end is configured for auto/auto and the other is not then the standard says the auto/auto end has to assume it is half duplex.

So it is very common for a provider to configure a link 100/full - and if you leave your end auto/auto will will fall back to 100/half.

So make sure you configure your end 100 full to [almost certainly] match what your provider has configured.

Also note that SFPs don't usually support speed negotiation.  However I am not sure in the case of this specific SFP - but I would not have high hopes.

It is pretty rare to get routers with actual 100Mb/s ports these days.  You could ask your provider if the port is Gigabit capable, and if so, could they change it to auto/auto. This would make your life much easier.

[Slider]

Hi Philip,

Just to confirm again, the MX250 WAN port supports a 1 Gbe SFP copper Module if the ISP provides a 1Gbps ethernet handoff correct?

[dqsg22]

Thanks for adding your experience. It looks like I should probably give the ISP a call.