| Author |
Message |
Guest
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 Posted:
Wed Aug 24, 2005 12:20 am Post subject:
autonegotiation and media converters |
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Folks,
I've got a question concerning media converters and autonegotiation.
Consider the following diagram (a fixed width font will help):
----------- tp ------ fiber ------ tp ------------
| switch1 |-------| MC1| ============== | MC2|--------| switch2 |
----------- ------ ------ ------------
tp - twisted pair
MC - media converter
Assume the media converters are not of the bridge variety. If switch1
were set to autonegotiate, but MC1 was not, would the link code word
be sent across the fiber link and on to switch2? Presumably if that
were true, it would be important that MC2 be configured similarly so
that switch2's link code word would propagate to switch1.
thanks for any clarity you can provide,
mb |
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Guest
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| Posted:
Wed Aug 24, 2005 12:20 am Post subject:
Re: autonegotiation and media converters |
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ok, trying to post with a browser is a big pain. hopefully you can
make out that the diagram shows switch1 connected via twisted pair to
MC1, which is connected via fiber to MC2 which is connected via twisted
pair to switch2. |
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JD
Guest
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| Posted:
Wed Aug 24, 2005 8:20 am Post subject:
Re: autonegotiation and media converters |
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mark.boolootian@gmail.com wrote:
| Quote: | Folks,
I've got a question concerning media converters and autonegotiation.
Consider the following diagram (a fixed width font will help):
----------- tp ------ fiber ------ tp ------------
| switch1 |-------| MC1| ============== | MC2|--------| switch2 |
----------- ------ ------ ------------
tp - twisted pair
MC - media converter
Assume the media converters are not of the bridge variety. If switch1
were set to autonegotiate, but MC1 was not, would the link code word
be sent across the fiber link and on to switch2? Presumably if that
were true, it would be important that MC2 be configured similarly so
that switch2's link code word would propagate to switch1.
thanks for any clarity you can provide,
mb
Mark, |
My limited experince says Murphy will stick his head in there. We had
varying results (Allied Telesyn) where sometimes the auto negotiation
would work, sometimes not. And we're talking about the same pair of
machines, one restart they negotiated properly, the next it didn't.
Allied makes a converter for the 100 meg that is basically a 2 port
switch - that type of converter does fairly well. If it's a fiber
switch feeding a convert to a copper host/switch, the negotiation
generally works. The configuration you ask for is ususally begging for
the settings to be forced at the swtiches.
Jay Drew |
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Manfred Kwiatkowski
Guest
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| Posted:
Wed Aug 24, 2005 4:20 pm Post subject:
Re: autonegotiation and media converters |
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In article <1124839571.549698.262990@g14g2000cwa.googlegroups.com>,
mark.boolootian@gmail.com writes:
| Quote: | Folks,
I've got a question concerning media converters and autonegotiation.
Consider the following diagram (a fixed width font will help):
----------- tp ------ fiber ------ tp ------------
| switch1 |-------| MC1| ============== | MC2|--------| switch2 |
----------- ------ ------ ------------
tp - twisted pair
MC - media converter
Assume the media converters are not of the bridge variety. If switch1
were set to autonegotiate, but MC1 was not, would the link code word
be sent across the fiber link and on to switch2? Presumably if that
were true, it would be important that MC2 be configured similarly so
that switch2's link code word would propagate to switch1.
|
As there is no autonegotiation defined on a 100BaseFX any possible
negotiation is local to the switch and its adjacent converter.
If the switches are mangeable and are set to a fixed configuration
everething is fine.
To be usefull with autonegotiating-only switches as well todays
mdiaconverters negotitiate full-duplex unconditionally. This
way the configurations kids tend to have at home will work
automagically.
On the other hand, awkward onfigurations like a n-way switch to
a fast ethernet hub will not work at all using such gear.
--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de |
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Guest
|
| Posted:
Wed Aug 24, 2005 10:00 pm Post subject:
Re: autonegotiation and media converters |
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Manfred Kwiatkowski wrote:
| Quote: | As there is no autonegotiation defined on a 100BaseFX any possible
negotiation is local to the switch and its adjacent converter.
|
This is exactly my question. Jay's yielding to Murphy aside, if the
immediately adjacent converter is not autonegotiating, isn't it true
that the autonegotiation would then happen with the remote switch?
Autonegotiation consists of sending a 16-bit link code word
adverstising
capabilities. I'm assuming, and have some empirical evidence
confirming,
that if the adjacent converter isn't autonegotiating, it is going to
just pass the link code word on, making its way to the remote switch.
One possible problem, which may have to do with Jay's observations,
is that if the remote converter is set to autonegotiate, the remote
switch will be receiving link code words from the near switch *and*
the remote converter. Worse, the link code words sent by the remote
switch will be consumed by the remote converter, leaving the near
switch to assume the neighbor isn't autonegotiating (which ends up
being true).
thanks for the responses,
mb |
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Manfred Kwiatkowski
Guest
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| Posted:
Thu Aug 25, 2005 2:56 pm Post subject:
Re: autonegotiation and media converters |
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In article <1124902841.120808.155470@g49g2000cwa.googlegroups.com>,
mark.boolootian@gmail.com writes:
| Quote: | Manfred Kwiatkowski wrote:
As there is no autonegotiation defined on a 100BaseFX any possible
negotiation is local to the switch and its adjacent converter.
This is exactly my question. Jay's yielding to Murphy aside, if the
immediately adjacent converter is not autonegotiating, isn't it true
that the autonegotiation would then happen with the remote switch?
Autonegotiation consists of sending a 16-bit link code word
adverstising
capabilities. I'm assuming, and have some empirical evidence
confirming,
that if the adjacent converter isn't autonegotiating, it is going to
just pass the link code word on, making its way to the remote switch.
|
No. The code word cannot make it to the other side as there is no
FLP defined on fiber.
| Quote: | One possible problem, which may have to do with Jay's observations,
is that if the remote converter is set to autonegotiate, the remote
switch will be receiving link code words from the near switch *and*
the remote converter. Worse, the link code words sent by the remote
switch will be consumed by the remote converter, leaving the near
switch to assume the neighbor isn't autonegotiating (which ends up
being true).
|
The autonegotiation is independent of the fiber side and soley
a matter of the hardware configuration of the MC.
There may be difficulties with link establishment (oszillations)
due to "missing link" features and/or auto-mdix specially if the
capaciators in the MC start to degrade.
--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de |
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