Switching

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

If I am reading this right, you tried a Juniper SFP module in a HP switch? If so, that will most likely be your biggest problem. HP switches (and servers for that matter) are notoriously temperamental when it comes to what SFP modules you put in, almost as bad as Cisco. If your switches are close together like in the same or adjacent racks, you can usually get away with using HP DAC cables as I've found most Juniper switches and Dell servers will work happily with HP DAC cables. If that is not an option, you'll need a HP compatible SFP module for the HP switch end. Rather than cough up the outrageous proces for a genuine HP SFP, I use cheap units from F5 that just work with great success. Who knows, now HP bought out Juniper, maybe HP firmware will be a bit more friendly towards Juniper products... one day! 

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

Ian, can you set the port speed in the chassis configuration?

set chassis fpc 0 pic 1 port 1 speed 1g

different flavours of Juniper do this in different ways and I've never used an EX4000 before.

Craig, the 5120 does not support autonegotiation on 1G fibre optics, so you may have been running into that, from https://supportportal.juniper.net/s/article/QFX-EX-Configuring-1G-and-25G-ports-on-QFX5120-48Y-M-and-EX4650-48Y:

EX4400 EX4400-EM-4S extension module, QFX5120-48Y(M) and EX4650-48Y do not support auto-negotiation for 1 Gigabit fiber SFP transceivers. In such cases, it is recommended to disable auto-negotiation on the remote end device.

Example on how to disable auto-negotiation in Junos OS:

    set interfaces ge-0/0/0 speed 1g    set interfaces ge-0/0/0 link-mode full-duplex    set interfaces ge-0/0/0 ether-options no-auto-negotiation

Martin

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

Interesting.  I have several cases where I have this auto negotiation configured and working with no issue, including this port. However, this particular port is now connecting directly into the carrier CPE.  I also find it interesting that if you do a show interface on this port is shows:

  Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Full-duplex, Speed: 1000mbps, Source filtering: Disabled

  Link-mode: Full-duplex, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Flow control: Disabled,

  Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled, Auto-MDIX: Enabled

I would have thought that if it was not supported it would have said something other that Auto-negotiation: Enabled.

Ian, can you set the port speed in the chassis configuration?

set chassis fpc 0 pic 1 port 1 speed 1g

different flavours of Juniper do this in different ways and I've never used an EX4000 before.

Craig, the 5120 does not support autonegotiation on 1G fibre optics, so you may have been running into that, from https://supportportal.juniper.net/s/article/QFX-EX-Configuring-1G-and-25G-ports-on-QFX5120-48Y-M-and-EX4650-48Y:

EX4400 EX4400-EM-4S extension module, QFX5120-48Y(M) and EX4650-48Y do not support auto-negotiation for 1 Gigabit fiber SFP transceivers. In such cases, it is recommended to disable auto-negotiation on the remote end device.

Example on how to disable auto-negotiation in Junos OS:

    set interfaces ge-0/0/0 speed 1g    set interfaces ge-0/0/0 link-mode full-duplex    set interfaces ge-0/0/0 ether-options no-auto-negotiation

Martin

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

It looks like the link I pasted earlier was busted, I just fixed that.

That output looks like it is for a copper GBIC, in which case this probably applies (from that previous link):

QFX5120-48Y(M)/EX4650-48Y switches with 1-gigabit copper SFP transceiver support auto-negotiation, as the physical layer within the transceiver handles auto-negotiation.

Interesting.  I have several cases where I have this auto negotiation configured and working with no issue, including this port. However, this particular port is now connecting directly into the carrier CPE.  I also find it interesting that if you do a show interface on this port is shows:

  Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Full-duplex, Speed: 1000mbps, Source filtering: Disabled

  Link-mode: Full-duplex, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Flow control: Disabled,

  Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled, Auto-MDIX: Enabled

I would have thought that if it was not supported it would have said something other that Auto-negotiation: Enabled.

Ian, can you set the port speed in the chassis configuration?

set chassis fpc 0 pic 1 port 1 speed 1g

different flavours of Juniper do this in different ways and I've never used an EX4000 before.

Craig, the 5120 does not support autonegotiation on 1G fibre optics, so you may have been running into that, from https://supportportal.juniper.net/s/article/QFX-EX-Configuring-1G-and-25G-ports-on-QFX5120-48Y-M-and-EX4650-48Y:

EX4400 EX4400-EM-4S extension module, QFX5120-48Y(M) and EX4650-48Y do not support auto-negotiation for 1 Gigabit fiber SFP transceivers. In such cases, it is recommended to disable auto-negotiation on the remote end device.

Example on how to disable auto-negotiation in Junos OS:

    set interfaces ge-0/0/0 speed 1g    set interfaces ge-0/0/0 link-mode full-duplex    set interfaces ge-0/0/0 ether-options no-auto-negotiation

Martin

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

Thank you to you and the rest for your responses and suggestions.

We will test these suggestions and update you with how we got this to work.

Thanks for reading and responding.

It looks like the link I pasted earlier was busted, I just fixed that.

That output looks like it is for a copper GBIC, in which case this probably applies (from that previous link):

QFX5120-48Y(M)/EX4650-48Y switches with 1-gigabit copper SFP transceiver support auto-negotiation, as the physical layer within the transceiver handles auto-negotiation.

Interesting.  I have several cases where I have this auto negotiation configured and working with no issue, including this port. However, this particular port is now connecting directly into the carrier CPE.  I also find it interesting that if you do a show interface on this port is shows:

  Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Full-duplex, Speed: 1000mbps, Source filtering: Disabled

  Link-mode: Full-duplex, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Flow control: Disabled,

  Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled, Auto-MDIX: Enabled

I would have thought that if it was not supported it would have said something other that Auto-negotiation: Enabled.

Ian, can you set the port speed in the chassis configuration?

set chassis fpc 0 pic 1 port 1 speed 1g

different flavours of Juniper do this in different ways and I've never used an EX4000 before.

Craig, the 5120 does not support autonegotiation on 1G fibre optics, so you may have been running into that, from https://supportportal.juniper.net/s/article/QFX-EX-Configuring-1G-and-25G-ports-on-QFX5120-48Y-M-and-EX4650-48Y:

EX4400 EX4400-EM-4S extension module, QFX5120-48Y(M) and EX4650-48Y do not support auto-negotiation for 1 Gigabit fiber SFP transceivers. In such cases, it is recommended to disable auto-negotiation on the remote end device.

Example on how to disable auto-negotiation in Junos OS:

    set interfaces ge-0/0/0 speed 1g    set interfaces ge-0/0/0 link-mode full-duplex    set interfaces ge-0/0/0 ether-options no-auto-negotiation

Martin

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

------------------------------
IAN TRUNKFIELD
------------------------------

Dear All

Please see below code for solution that worked on our EX4000-48MP running JUNOS  25.2R1.9

set interfaces ge-0/1/3 native-vlan-id 1
set interfaces ge-0/1/3 speed 1g
set interfaces ge-0/1/3 link-mode full-duplex
set interfaces ge-0/1/3 ether-options no-auto-negotiation

Thank you to you and the rest for your responses and suggestions.

We will test these suggestions and update you with how we got this to work.

Thanks for reading and responding.

It looks like the link I pasted earlier was busted, I just fixed that.

That output looks like it is for a copper GBIC, in which case this probably applies (from that previous link):

QFX5120-48Y(M)/EX4650-48Y switches with 1-gigabit copper SFP transceiver support auto-negotiation, as the physical layer within the transceiver handles auto-negotiation.

Interesting.  I have several cases where I have this auto negotiation configured and working with no issue, including this port. However, this particular port is now connecting directly into the carrier CPE.  I also find it interesting that if you do a show interface on this port is shows:

  Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Link-mode: Full-duplex, Speed: 1000mbps, Source filtering: Disabled

  Link-mode: Full-duplex, BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Flow control: Disabled,

  Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled, Auto-MDIX: Enabled

I would have thought that if it was not supported it would have said something other that Auto-negotiation: Enabled.

Ian, can you set the port speed in the chassis configuration?

set chassis fpc 0 pic 1 port 1 speed 1g

different flavours of Juniper do this in different ways and I've never used an EX4000 before.

Craig, the 5120 does not support autonegotiation on 1G fibre optics, so you may have been running into that, from https://supportportal.juniper.net/s/article/QFX-EX-Configuring-1G-and-25G-ports-on-QFX5120-48Y-M-and-EX4650-48Y:

EX4400 EX4400-EM-4S extension module, QFX5120-48Y(M) and EX4650-48Y do not support auto-negotiation for 1 Gigabit fiber SFP transceivers. In such cases, it is recommended to disable auto-negotiation on the remote end device.

Example on how to disable auto-negotiation in Junos OS:

    set interfaces ge-0/0/0 speed 1g    set interfaces ge-0/0/0 link-mode full-duplex    set interfaces ge-0/0/0 ether-options no-auto-negotiation

Martin

Boy, does THIS sound familiar....

I work in a similar environment and have run into this issue a few times.  In my case it was a QFX 5120 connecting into an HP 5120, so that really set the stage for confusion when you work 100% remote.  
I see you went down the speed/duplex/auto negotiate route already, however, you didn't state if you disabled auto negotiation on one or both sides of the link? In my specific case, if I disabled the QFX  side and hard set duplex full, it would work.  Since Juniper is new to this shop, and the rest of the engineering staff are unfamiliar/uncomfortable with Juniper, this immediately made it a Juniper issue.  I was unable to convince them to allow me to move the auto negotiation from the HP side, reset the QFX interface to auto, and try again to prove out the problem.  Understand that the HP side of this link is a switch with 12 YEARS of up time, with software at least that old.  Being an old dude, I remembered SEVERAL vendors having the problem with auto neg in the early days of gigabit ethernet (Juniper and Cisco included, and was in the late 1990's early 2000's).  This eventually got corrected with updated optics and firmware on the switches.  This could still be your problem here.  One other thing to consider -- when you say "cannot be seen," are you referring to LLDP, or the actual VLAN traffic between the switches?  Is this link a trunk or a single VLAN (access link)? This can be an issue depending on the configuration of the HP side of the switch.  I am pretty sure that Juniper is the ONLY vendor that does NOT "define" VLAN1 everywhere.  HP will default to this as the "native" VLAN on a trunk link unless you remove it.  Since VLAN 1 is technically present on the Juniper side, but not defined, thus not listed as the native VLAN or in the list of allowed VLANS on the trunk, you could be discarding that inbound traffic. (VLAN 1 IS there, but if not explicitly defined, you cannot explicitly assign it to a trunk or access port.)
This last item is pretty tough to get your head around if you are new to Juniper -- lord knows I have spent multiple years trying to get my HP/Cisco co-workers to understand this.  Frankly, this is the reason I prefer Juniper to other vendors -- you have 100% control of what traverses the trunk without truly thinking about it. However, it does take some getting used to.

------------------------------
CRAIG DALRYMPLE

Original Message:
Sent: 10-20-2025 03:06
From: IAN TRUNKFIELD
Subject: Uplink issue

Hello,

I'm new to using Juniper EX switches and have run into an odd issue.

I have EX4000-48MP and wanted to connect an HP J9626A switch. we only need to connect via 1Gbps fibre. We bought Juniper SFP-1G-SX-C for use in the Juniper switch.

Problem is the HP cannot be seen by the Juniper switch, we have tested from Juniper to Juniper via the SFP-1G-SX-C and that works, but not between Juniper and HP.

We have manually set the SFP speed and duplex rate to match the HP and have tried both GE-0/1/2 and GE-0/1/3 SFTP uplink ports.

Does anyone in the community experienced this or knows how to resolve?

Thanks for reading.

Ian

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IAN TRUNKFIELD
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