Full duplex and a hub
Hi ALL, a fast Ether port on a cisco switch (2900XL) connected to a hub (3com repeater) 10/100 port reports auto-negotiated full-duplex, and works fine. How can a normal hub (no buffering!) accept full-duplex? To my undestanding this is impossible... Am I wrong? And, is there a simple way to check the duplex mode of a line by some IOS-independent method? Thanks. Alex == _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Full duplex and a hub
some 3com models include an optional uplink module which function as a
switching port... are you refering to the port?
you can use: show port capabilities {port}
correct me if i am wrong...
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Sasha
Sent: Wednesday, March 14, 2001 5:24 PM
To: [EMAIL PROTECTED]
Subject: Full duplex and a hub
Hi ALL,
a fast Ether port on a cisco switch (2900XL)
connected to a hub (3com repeater) 10/100 port
reports auto-negotiated full-duplex, and works fine.
How can a normal hub (no buffering!) accept full-duplex?
To my undestanding this is impossible...
Am I wrong?
And, is there a simple way to check the duplex mode
of a line by some IOS-independent method?
Thanks.
Alex
==
_
FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
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RE: Full duplex and a hub
oops sorry should be: show port {port}
to check the speed.
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Sasha
Sent: Wednesday, March 14, 2001 5:24 PM
To: [EMAIL PROTECTED]
Subject: Full duplex and a hub
Hi ALL,
a fast Ether port on a cisco switch (2900XL)
connected to a hub (3com repeater) 10/100 port
reports auto-negotiated full-duplex, and works fine.
How can a normal hub (no buffering!) accept full-duplex?
To my undestanding this is impossible...
Am I wrong?
And, is there a simple way to check the duplex mode
of a line by some IOS-independent method?
Thanks.
Alex
==
_
FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
_
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Full duplex and a hub
Never seen that on a hub (hubs should of course not work with duplex) However, I have seen this 'faking full-duplex' in other situations. Lights on the switch (and the routers) indicated full duplex but data transfers (in different directions at the same time) seemed slow. I cleared the counters on the interfaces then inititiated massive transfers in both directions. This was to see if any collisions showed up in "sh int" (indicating that the full-duplex lights were 'full of it' [to use a tech term]). The collision count soared. Cisco confirmed that this was an effective (albeit screwy) way to confirm duplex status (or the lack thereof) notwithstanding the status lights. Although that test is not IOS-independent, it should work. My cure was to upgrade the IOS on the routers. >From: "Sasha" <[EMAIL PROTECTED]> >Reply-To: "Sasha" <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: Full duplex and a hub >Date: Wed, 14 Mar 2001 10:24:19 +0100 > >Hi ALL, >a fast Ether port on a cisco switch (2900XL) >connected to a hub (3com repeater) 10/100 port >reports auto-negotiated full-duplex, and works fine. >How can a normal hub (no buffering!) accept full-duplex? >To my undestanding this is impossible... >Am I wrong? >And, is there a simple way to check the duplex mode >of a line by some IOS-independent method? >Thanks. >Alex >== > > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get your FREE download of MSN Explorer at http://explorer.msn.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Full duplex and a hub
>Hi ALL, >a fast Ether port on a cisco switch (2900XL) >connected to a hub (3com repeater) 10/100 port >reports auto-negotiated full-duplex, and works fine. >How can a normal hub (no buffering!) accept full-duplex? >To my undestanding this is impossible... >Am I wrong? The real problem here is that "hub" is a marketing, not a technical, term. In most technical discussions, what we mean by an Ethernet hub is a multiport repeater. If the 3Com device were defined as a multiport repeater, what you say would be completely true. Unfortunately, different vendors use "hub" in different ways. Cisco, actually, has been cleaner than most. When Cisco puts a capability into a "hub" that flatly is beyond the functionality of a multiport repeater, they tend to identify that as a distinct function, and often put that on a separate module. A good example of that is speed switching. Cabletron, as an example, tends to define "hub" as a shelf into which repeater, bridge/LAN switch, and router modules can plug. I can't say they strictly are wrong to do so, because there is no standard definition of hub. Their definition is more a logical one that it is a hubbing point for wiring, rather than phrased in terms of what happens to the bits on the wire. Interestingly, until Cabletron and Cisco got into a rather nasty and public licensing fight several years ago, Cabletron was quite possibly Cisco's largest customer for card-level IGS routers used in their hubs, and carrying a Cabletron part number. Not sure if Cabletron (or its successor companies) now makes its own router cards, or, if not, from whome they OEM them. My impression is that 3Com uses the term hub in a way fairly consistent with Cabletron. -- "What Problem are you trying to solve?" ***send Cisco questions to the list, so all can benefit -- not directly to me*** Howard C. Berkowitz [EMAIL PROTECTED] Technical Director, CertificationZone.com Senior Mgr. IP Protocols & Algorithms, Advanced Technology Investments, NortelNetworks (for ID only) but Cisco stockholder! "retired" Certified Cisco Systems Instructor (CID) #93005 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Full duplex and a hub
>From: "Howard C. Berkowitz" <[EMAIL PROTECTED]> >Reply-To: "Howard C. Berkowitz" <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: Re: Full duplex and a hub >Date: Wed, 14 Mar 2001 09:09:46 -0500 > >Interestingly, until Cabletron and Cisco got into a rather nasty and >public licensing fight several years ago, Cabletron was quite >possibly Cisco's largest customer for card-level IGS routers used in >their hubs, and carrying a Cabletron part number. Not sure if >Cabletron (or its successor companies) now makes its own router >cards, or, if not, from whome they OEM them. ACC (Now Ericsson) I believe. Rob./ _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Full duplex and a hub
Indeed, 3COM has a product called "full-duplex repeater" (what a name...). This is actually a hybrid of a switch and a repeater: it uses buffering of incoming frames and a round-robin method of forwarding them to all egress ports. However, my question concerns the common device -- no buffering. How can the port controller on cisco claim it is in full-duplex while it is in half? Is it possible that 3COM "emulates" full-duplex during autonegotiation, and, if yes, what for? == ""Howard C. Berkowitz"" <[EMAIL PROTECTED]> escribió en el mensaje news:p0500190eb6d52a4dc981@[63.216.127.100]... > >Hi ALL, > >a fast Ether port on a cisco switch (2900XL) > >connected to a hub (3com repeater) 10/100 port > >reports auto-negotiated full-duplex, and works fine. > >How can a normal hub (no buffering!) accept full-duplex? > >To my undestanding this is impossible... > >Am I wrong? > > > The real problem here is that "hub" is a marketing, not a technical, > term. In most technical discussions, what we mean by an Ethernet hub > is a multiport repeater. If the 3Com device were defined as a > multiport repeater, what you say would be completely true. > > Unfortunately, different vendors use "hub" in different ways. Cisco, > actually, has been cleaner than most. When Cisco puts a capability > into a "hub" that flatly is beyond the functionality of a multiport > repeater, they tend to identify that as a distinct function, and > often put that on a separate module. A good example of that is speed > switching. > > Cabletron, as an example, tends to define "hub" as a shelf into which > repeater, bridge/LAN switch, and router modules can plug. I can't say > they strictly are wrong to do so, because there is no standard > definition of hub. Their definition is more a logical one that it is > a hubbing point for wiring, rather than phrased in terms of what > happens to the bits on the wire. > > Interestingly, until Cabletron and Cisco got into a rather nasty and > public licensing fight several years ago, Cabletron was quite > possibly Cisco's largest customer for card-level IGS routers used in > their hubs, and carrying a Cabletron part number. Not sure if > Cabletron (or its successor companies) now makes its own router > cards, or, if not, from whome they OEM them. > > My impression is that 3Com uses the term hub in a way fairly > consistent with Cabletron. > -- > "What Problem are you trying to solve?" > ***send Cisco questions to the list, so all can benefit -- not > directly to me*** > > Howard C. Berkowitz [EMAIL PROTECTED] > Technical Director, CertificationZone.com > Senior Mgr. IP Protocols & Algorithms, Advanced Technology Investments, > NortelNetworks (for ID only) but Cisco stockholder! > "retired" Certified Cisco Systems Instructor (CID) #93005 > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
