Mailing List Archive

EX4300 and full-duplex-only
Does anyone know the backstory to this? We just found out this platform
doesn't support half-duplex - at all - and it was an unpleasant
surprise, as it means some old SCADA and instrumentation can't link-up
against an EX4300.

I'm assuming they skimped and left out the hardware for detecting RX and
queueing TX, but wonder if there's something I'm missing.

Cheers,
Phil
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Re: EX4300 and full-duplex-only [ In reply to ]
Really? So you can't use EX4300 at 10 Mbps (I don't know of any
devices that support 10/Full)? If this is true, it is a
purchase-stopper for us.

On Wed, Sep 23, 2015 at 01:58:36PM +0100, Phil Mayers wrote:
> Does anyone know the backstory to this? We just found out this
> platform doesn't support half-duplex - at all - and it was an
> unpleasant surprise, as it means some old SCADA and instrumentation
> can't link-up against an EX4300.
>
> I'm assuming they skimped and left out the hardware for detecting RX
> and queueing TX, but wonder if there's something I'm missing.
>
> Cheers,
> Phil
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Re: EX4300 and full-duplex-only [ In reply to ]
> On 23 Sep 2015, at 15:30, Chuck Anderson <cra@WPI.EDU> wrote:
>
> Really? So you can't use EX4300 at 10 Mbps (I don't know of any
> devices that support 10/Full)? If this is true, it is a
> purchase-stopper for us.
>
> On Wed, Sep 23, 2015 at 01:58:36PM +0100, Phil Mayers wrote:
>> Does anyone know the backstory to this? We just found out this
>> platform doesn't support half-duplex - at all - and it was an
>> unpleasant surprise, as it means some old SCADA and instrumentation
>> can't link-up against an EX4300.
>>
>> I'm assuming they skimped and left out the hardware for detecting RX
>> and queueing TX, but wonder if there's something I'm missing.

On the link:
http://www.juniper.net/documentation/en_US/junos13.2/topics/task/configuration/ex-series-gigabit-interfaces-cli-els.html#jd0e111

There is only a note of duplex, not about the speed:
Note: On EX4300 switches, the interfaces operate in full duplex mode only.

I do see on a EX4300 some links in 100Mb and 1000Mb, don’t have 10Mb devices attached.

Not sure why this is.


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Re: EX4300 and full-duplex-only [ In reply to ]
On 23/09/15 14:30, Chuck Anderson wrote:
> Really? So you can't use EX4300 at 10 Mbps (I don't know of any
> devices that support 10/Full)? If this is true, it is a
> purchase-stopper for us.

10/full works fine.

10/half (or 100/half) does NOT work:

http://www.juniper.net/documentation/en_US/junos13.2/topics/task/configuration/ex-series-gigabit-interfaces-cli-els.html

"""
Note: On EX4300 switches, the interfaces operate in full duplex mode only.
"""

We've confirmed this by inspecting the autoneg caps advertised from the
device; all half-duplex modes are absent.
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Re: EX4300 and full-duplex-only [ In reply to ]
On 23/09/15 14:38, Peter Tavenier wrote:

> There is only a note of duplex, not about the speed:

Indeed.

> Note: On EX4300 switches, the interfaces operate in full duplex mode only.
>
> I do see on a EX4300 some links in 100Mb and 1000Mb, don’t have 10Mb devices attached.
>
> Not sure why this is.

If you mean "why it's only duplex limitations", I'm guessing the device
is missing the collision-detect/retransmit hardware for cost reasons.
10/half is pretty rare these days and, in theory, they're pitched as a
datacentre device (though we have an IBM tape library which is 10/half
on it's management port).

You can force the link up by disabling autoneg, but that comes up
duplex-mismatched - 10/full at the EX end, 10/half at the device end.

All very disappointing; we did not think to specify "must comply with
IEEE 802.3" in the RFP :o/
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Re: EX4300 and full-duplex-only [ In reply to ]
On 09/23/2015 09:47 AM, Phil Mayers wrote:
> If you mean "why it's only duplex limitations", I'm guessing the device is
> missing the collision-detect/retransmit hardware for cost reasons. 10/half is
> pretty rare these days and, in theory, they're pitched as a datacentre device
> (though we have an IBM tape library which is 10/half on it's management port).

When I first saw the details about the EX4300, my initial reaction was that it
was built as a low cost 1Gb dongle for QFabric.

> You can force the link up by disabling autoneg, but that comes up
> duplex-mismatched - 10/full at the EX end, 10/half at the device end.
>
> All very disappointing; we did not think to specify "must comply with IEEE
> 802.3" in the RFP :o/


Even putting it in wouldn't have helped unless you verified it yourself anyway
- they list 802.3 support on page 19 of the data sheet:

http://www.juniper.net/assets/us/en/local/pdf/datasheets/1000467-en.pdf

That said, does anyone know if the EX3300 switches suffer from this same
design decision?

--
Frank Sweetser fs at wpi.edu | For every problem, there is a solution that
Manager of Network Operations | is simple, elegant, and wrong.
Worcester Polytechnic Institute | - HL Mencken
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Re: EX4300 and full-duplex-only [ In reply to ]
The ex3300 does not have this limitation.


William Jackson

Gibtelecom
Email: william.jackson@gibtele.com

-----Original Message-----
From: juniper-nsp [mailto:juniper-nsp-bounces@puck.nether.net] On Behalf Of Frank Sweetser
Sent: 23 September 2015 18:05
To: juniper-nsp@puck.nether.net
Subject: Re: [j-nsp] EX4300 and full-duplex-only

On 09/23/2015 09:47 AM, Phil Mayers wrote:
> If you mean "why it's only duplex limitations", I'm guessing the
> device is missing the collision-detect/retransmit hardware for cost
> reasons. 10/half is pretty rare these days and, in theory, they're
> pitched as a datacentre device (though we have an IBM tape library which is 10/half on it's management port).

When I first saw the details about the EX4300, my initial reaction was that it was built as a low cost 1Gb dongle for QFabric.

> You can force the link up by disabling autoneg, but that comes up
> duplex-mismatched - 10/full at the EX end, 10/half at the device end.
>
> All very disappointing; we did not think to specify "must comply with
> IEEE 802.3" in the RFP :o/


Even putting it in wouldn't have helped unless you verified it yourself anyway
- they list 802.3 support on page 19 of the data sheet:

http://www.juniper.net/assets/us/en/local/pdf/datasheets/1000467-en.pdf

That said, does anyone know if the EX3300 switches suffer from this same design decision?

--
Frank Sweetser fs at wpi.edu | For every problem, there is a solution that
Manager of Network Operations | is simple, elegant, and wrong.
Worcester Polytechnic Institute | - HL Mencken
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Re: EX4300 and full-duplex-only [ In reply to ]
On 28/09/15 11:52, Jackson, William wrote:
> The ex3300 does not have this limitation.
>

FWIW, Juniper have come back and said this is a firmware limitation in
the PHY. Apparently it's some sort of feature conflict or code space
issue w.r.t. MACSEC, and there is some vague possibility of a release
with an either/or MACSEC/half-duplex in the future.

:o/

Agree the 3300 has no such limitation.
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