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Any Help Appreciated... CCNA Question
|
|
| Karim M Ladhu 2002-08-28, 2:28 pm |
| Hello,
I am studying for CCNA and was confused after reading
about Half Duplex and Duplex network configurations...
When 2 nodes are connected back to back this is duplex, I
understand that fine... my actual question was regarding the
Bus network topology which is Half Duplex... when multiple
devices are connected to a HUB is this classed as Half
Duplex or Full Duplex - is this a practical form of A Bus
topology? - Does this differ when devices are connected to a
Switch... if so - how?
My other question was about network communication, from
what I can gather, IP addresses are only required to resolve
MAC addresses and Hostnames and to cross over from one
lan to the other through a gateway. Actual communication
within a LAN uses MAC addresses which are stored in cache
on the individual computers so that each time communication
takes place it need not start with an ARP broadcast to reduce
network traffic... now if you connect devices using a hub -
everytime you begin communicating... will you not always have
to start with a broadcast? How will the computer know which
port the destination computer is connected to on the hub? If you
connect devices using a switch how is this different?
.... As you can see I am totally lost and probably more confused
than I think I am!
Please Advise!
Thanking you in advance, Karim.
| |
| Mark M. Reed 2002-08-28, 2:28 pm |
| in regards to your second question:
Mac addresses are stored locally in ARP cache..yes... they remain there for
e predetermined timeframe then timeout if no communication is made to that
host.
When all the hosts start up..for example at a business at 8am... there are
no arp entries... whenever comm needs to occur between a host, an ARP
broadcast is made... WHO HAS (X)? it is picked up by each host on that
physical media and they each examine it for a reply... if they are not X,
they drop it ...X however responds.. I AM X. This response is what allows
the requesting host to make an ARP entry.
You mention a hub... remeber a hub is just a multiport repeater..broadcasts
flow thru a hub. It works basically the same way with a switch..but a
switch will learn the MACs just like a host to build its switching tables.
The switch does not have a table entry for MAC X... it sends it to all and
waits for the owner to reply..it them makes its entry.
You can also physically enter ARP mappings under the windows DOS CLI.
Do an ARP /? and look at all the options.
Another great way to visualize this is to download the sniffer ETHEREAL and
watch the packets on your network... you will see this process in
realtime...that is very helpful. Do a search on ETHEREAL.. its a shareware
sniffer.
Mark M. Reed
"Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
> My other question was about network communication, from
> what I can gather, IP addresses are only required to resolve
> MAC addresses and Hostnames and to cross over from one
> lan to the other through a gateway. Actual communication
> within a LAN uses MAC addresses which are stored in cache
> on the individual computers so that each time communication
> takes place it need not start with an ARP broadcast to reduce
> network traffic... now if you connect devices using a hub -
> everytime you begin communicating... will you not always have
> to start with a broadcast? How will the computer know which
> port the destination computer is connected to on the hub? If you
> connect devices using a switch how is this different?
>
> ... As you can see I am totally lost and probably more confused
> than I think I am!
>
> Please Advise!
>
> Thanking you in advance, Karim.
>
>
>
| |
| Karim M Ladhu 2002-08-28, 2:28 pm |
| Thanks for your reply...
If a switch has already learned the MAC addresses for each node connected
to each of its interfaces... how is this used by PC's ? - is it used ?
If you use a Hub will you need to broadcast before each communication
attempt to recognise the port on the hub... ?
How does a switch work with PC's to reduce network traffic?
From what somebody else told me, when communicating via a Hub you
must broadcast each time to identify the destination computer information,
when using a switch, the switch stores this information so it is not
necessary
to broadcast... is this true? if so does the switch prevent the broadcast by
replying itself? Is this an ARP broadcast which it prevents?
Thanks again, Karim
"Mark M. Reed" <mreed@reedassociates.com> wrote in message
news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
> in regards to your second question:
>
> Mac addresses are stored locally in ARP cache..yes... they remain there
for
> e predetermined timeframe then timeout if no communication is made to that
> host.
>
> When all the hosts start up..for example at a business at 8am... there are
> no arp entries... whenever comm needs to occur between a host, an ARP
> broadcast is made... WHO HAS (X)? it is picked up by each host on that
> physical media and they each examine it for a reply... if they are not X,
> they drop it ...X however responds.. I AM X. This response is what allows
> the requesting host to make an ARP entry.
>
> You mention a hub... remeber a hub is just a multiport
repeater..broadcasts
> flow thru a hub. It works basically the same way with a switch..but a
> switch will learn the MACs just like a host to build its switching tables.
>
> The switch does not have a table entry for MAC X... it sends it to all and
> waits for the owner to reply..it them makes its entry.
>
> You can also physically enter ARP mappings under the windows DOS CLI.
>
> Do an ARP /? and look at all the options.
>
> Another great way to visualize this is to download the sniffer ETHEREAL
and
> watch the packets on your network... you will see this process in
> realtime...that is very helpful. Do a search on ETHEREAL.. its a
shareware
> sniffer.
>
> Mark M. Reed
>
>
>
>
> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>
> > My other question was about network communication, from
> > what I can gather, IP addresses are only required to resolve
> > MAC addresses and Hostnames and to cross over from one
> > lan to the other through a gateway. Actual communication
> > within a LAN uses MAC addresses which are stored in cache
> > on the individual computers so that each time communication
> > takes place it need not start with an ARP broadcast to reduce
> > network traffic... now if you connect devices using a hub -
> > everytime you begin communicating... will you not always have
> > to start with a broadcast? How will the computer know which
> > port the destination computer is connected to on the hub? If you
> > connect devices using a switch how is this different?
> >
> > ... As you can see I am totally lost and probably more confused
> > than I think I am!
> >
> > Please Advise!
> >
> > Thanking you in advance, Karim.
> >
> >
> >
>
>
| |
| Mark M. Reed 2002-08-28, 2:28 pm |
| See comments per line below:
"Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
> Thanks for your reply...
>
> If a switch has already learned the MAC addresses for each node
> connected to each of its interfaces... how is this used by PC's ? - is
> it used ?
a switch creates virtual circuits between two communicating devices rather
than sending out to everyone.
The PC sends it traffic to the destination... the switch takes that and
imagine it making a pass thru connection from the source port to the
destination port... no other ports on the switch see the traffic...
unlike a hub that is 'dumb'..it gets traffic and shoots it out all
ports...it knows nothing....
imagine a hub like a PA Intercom system... everyone hears it...and only
those that the message relates to pay attention.
Imagine a switch like a telephone operator... it takes a caller and
connects them to another person... no one else gets involved or hears it.
ROUGH ANALOGY! grin
>
> If you use a Hub will you need to broadcast before each communication
> attempt to recognise the port on the hub... ?
No... a broadcast will occur if the PC does not have an ARP entry... it it
does, no broadcast is needed...the data is sent on the wire... if a hub is
used...all PCs will see it, but only the destination will take it.
A switch will take it and send it out only the wire to the destination.
>
> How does a switch work with PC's to reduce network traffic?
Creates virtual circuits that stop the traffic from flowing on all parts of
the medium.
>
> From what somebody else told me, when communicating via a Hub you
> must broadcast each time to identify the destination computer
> information, when using a switch, the switch stores this information
> so it is not necessary
> to broadcast... is this true? if so does the switch prevent the
> broadcast by replying itself? Is this an ARP broadcast which it
> prevents?
No.. the above should explain why this is not true.
>
> Thanks again, Karim
>
> "Mark M. Reed" <mreed@reedassociates.com> wrote in message
> news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
>> in regards to your second question:
>>
>> Mac addresses are stored locally in ARP cache..yes... they remain
>> there
> for
>> e predetermined timeframe then timeout if no communication is made to
>> that host.
>>
>> When all the hosts start up..for example at a business at 8am...
>> there are no arp entries... whenever comm needs to occur between a
>> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
>> each host on that physical media and they each examine it for a
>> reply... if they are not X, they drop it ...X however responds.. I AM
>> X. This response is what allows the requesting host to make an ARP
>> entry.
>>
>> You mention a hub... remeber a hub is just a multiport
> repeater..broadcasts
>> flow thru a hub. It works basically the same way with a switch..but
>> a switch will learn the MACs just like a host to build its switching
>> tables.
>>
>> The switch does not have a table entry for MAC X... it sends it to
>> all and waits for the owner to reply..it them makes its entry.
>>
>> You can also physically enter ARP mappings under the windows DOS CLI.
>>
>> Do an ARP /? and look at all the options.
>>
>> Another great way to visualize this is to download the sniffer
>> ETHEREAL
> and
>> watch the packets on your network... you will see this process in
>> realtime...that is very helpful. Do a search on ETHEREAL.. its a
> shareware
>> sniffer.
>>
>> Mark M. Reed
>>
>>
>>
>>
>> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>>
>> > My other question was about network communication, from
>> > what I can gather, IP addresses are only required to resolve
>> > MAC addresses and Hostnames and to cross over from one
>> > lan to the other through a gateway. Actual communication
>> > within a LAN uses MAC addresses which are stored in cache
>> > on the individual computers so that each time communication
>> > takes place it need not start with an ARP broadcast to reduce
>> > network traffic... now if you connect devices using a hub -
>> > everytime you begin communicating... will you not always have
>> > to start with a broadcast? How will the computer know which
>> > port the destination computer is connected to on the hub? If you
>> > connect devices using a switch how is this different?
>> >
>> > ... As you can see I am totally lost and probably more confused
>> > than I think I am!
>> >
>> > Please Advise!
>> >
>> > Thanking you in advance, Karim.
>> >
>> >
>> >
>>
>>
>
>
>
| |
| Karim M Ladhu 2002-08-28, 3:28 pm |
| Thanks for your reply...
If a switch has already learned the MAC addresses for each node connected
to each of its interfaces... how is this used by PC's ? - is it used ?
If you use a Hub will you need to broadcast before each communication
attempt to recognise the port on the hub... ?
How does a switch work with PC's to reduce network traffic?
From what somebody else told me, when communicating via a Hub you
must broadcast each time to identify the destination computer information,
when using a switch, the switch stores this information so it is not
necessary
to broadcast... is this true? if so does the switch prevent the broadcast by
replying itself? Is this an ARP broadcast which it prevents?
Thanks again, Karim
"Mark M. Reed" <mreed@reedassociates.com> wrote in message
news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
> in regards to your second question:
>
> Mac addresses are stored locally in ARP cache..yes... they remain there
for
> e predetermined timeframe then timeout if no communication is made to that
> host.
>
> When all the hosts start up..for example at a business at 8am... there are
> no arp entries... whenever comm needs to occur between a host, an ARP
> broadcast is made... WHO HAS (X)? it is picked up by each host on that
> physical media and they each examine it for a reply... if they are not X,
> they drop it ...X however responds.. I AM X. This response is what allows
> the requesting host to make an ARP entry.
>
> You mention a hub... remeber a hub is just a multiport
repeater..broadcasts
> flow thru a hub. It works basically the same way with a switch..but a
> switch will learn the MACs just like a host to build its switching tables.
>
> The switch does not have a table entry for MAC X... it sends it to all and
> waits for the owner to reply..it them makes its entry.
>
> You can also physically enter ARP mappings under the windows DOS CLI.
>
> Do an ARP /? and look at all the options.
>
> Another great way to visualize this is to download the sniffer ETHEREAL
and
> watch the packets on your network... you will see this process in
> realtime...that is very helpful. Do a search on ETHEREAL.. its a
shareware
> sniffer.
>
> Mark M. Reed
>
>
>
>
> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>
> > My other question was about network communication, from
> > what I can gather, IP addresses are only required to resolve
> > MAC addresses and Hostnames and to cross over from one
> > lan to the other through a gateway. Actual communication
> > within a LAN uses MAC addresses which are stored in cache
> > on the individual computers so that each time communication
> > takes place it need not start with an ARP broadcast to reduce
> > network traffic... now if you connect devices using a hub -
> > everytime you begin communicating... will you not always have
> > to start with a broadcast? How will the computer know which
> > port the destination computer is connected to on the hub? If you
> > connect devices using a switch how is this different?
> >
> > ... As you can see I am totally lost and probably more confused
> > than I think I am!
> >
> > Please Advise!
> >
> > Thanking you in advance, Karim.
> >
> >
> >
>
>
| |
| Mark M. Reed 2002-08-28, 3:28 pm |
| See comments per line below:
"Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
> Thanks for your reply...
>
> If a switch has already learned the MAC addresses for each node
> connected to each of its interfaces... how is this used by PC's ? - is
> it used ?
a switch creates virtual circuits between two communicating devices rather
than sending out to everyone.
The PC sends it traffic to the destination... the switch takes that and
imagine it making a pass thru connection from the source port to the
destination port... no other ports on the switch see the traffic...
unlike a hub that is 'dumb'..it gets traffic and shoots it out all
ports...it knows nothing....
imagine a hub like a PA Intercom system... everyone hears it...and only
those that the message relates to pay attention.
Imagine a switch like a telephone operator... it takes a caller and
connects them to another person... no one else gets involved or hears it.
ROUGH ANALOGY! grin
>
> If you use a Hub will you need to broadcast before each communication
> attempt to recognise the port on the hub... ?
No... a broadcast will occur if the PC does not have an ARP entry... it it
does, no broadcast is needed...the data is sent on the wire... if a hub is
used...all PCs will see it, but only the destination will take it.
A switch will take it and send it out only the wire to the destination.
>
> How does a switch work with PC's to reduce network traffic?
Creates virtual circuits that stop the traffic from flowing on all parts of
the medium.
>
> From what somebody else told me, when communicating via a Hub you
> must broadcast each time to identify the destination computer
> information, when using a switch, the switch stores this information
> so it is not necessary
> to broadcast... is this true? if so does the switch prevent the
> broadcast by replying itself? Is this an ARP broadcast which it
> prevents?
No.. the above should explain why this is not true.
>
> Thanks again, Karim
>
> "Mark M. Reed" <mreed@reedassociates.com> wrote in message
> news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
>> in regards to your second question:
>>
>> Mac addresses are stored locally in ARP cache..yes... they remain
>> there
> for
>> e predetermined timeframe then timeout if no communication is made to
>> that host.
>>
>> When all the hosts start up..for example at a business at 8am...
>> there are no arp entries... whenever comm needs to occur between a
>> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
>> each host on that physical media and they each examine it for a
>> reply... if they are not X, they drop it ...X however responds.. I AM
>> X. This response is what allows the requesting host to make an ARP
>> entry.
>>
>> You mention a hub... remeber a hub is just a multiport
> repeater..broadcasts
>> flow thru a hub. It works basically the same way with a switch..but
>> a switch will learn the MACs just like a host to build its switching
>> tables.
>>
>> The switch does not have a table entry for MAC X... it sends it to
>> all and waits for the owner to reply..it them makes its entry.
>>
>> You can also physically enter ARP mappings under the windows DOS CLI.
>>
>> Do an ARP /? and look at all the options.
>>
>> Another great way to visualize this is to download the sniffer
>> ETHEREAL
> and
>> watch the packets on your network... you will see this process in
>> realtime...that is very helpful. Do a search on ETHEREAL.. its a
> shareware
>> sniffer.
>>
>> Mark M. Reed
>>
>>
>>
>>
>> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>>
>> > My other question was about network communication, from
>> > what I can gather, IP addresses are only required to resolve
>> > MAC addresses and Hostnames and to cross over from one
>> > lan to the other through a gateway. Actual communication
>> > within a LAN uses MAC addresses which are stored in cache
>> > on the individual computers so that each time communication
>> > takes place it need not start with an ARP broadcast to reduce
>> > network traffic... now if you connect devices using a hub -
>> > everytime you begin communicating... will you not always have
>> > to start with a broadcast? How will the computer know which
>> > port the destination computer is connected to on the hub? If you
>> > connect devices using a switch how is this different?
>> >
>> > ... As you can see I am totally lost and probably more confused
>> > than I think I am!
>> >
>> > Please Advise!
>> >
>> > Thanking you in advance, Karim.
>> >
>> >
>> >
>>
>>
>
>
>
| |
| Karim M Ladhu 2002-08-28, 3:28 pm |
| Thanks alot Mark,
That really clears up my second question...
Kind Regards, Karim
Note: Now im only 1/2 as confused as before :-) ...and yes, I did
like your analogy!
"Mark M. Reed" <mreed@reedassociates.com> wrote in message
news:Xns9278A4E4882A5mreedreed
associatesc@216.168.3.40...
> See comments per line below:
>
>
> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
>
> > Thanks for your reply...
> >
> > If a switch has already learned the MAC addresses for each node
> > connected to each of its interfaces... how is this used by PC's ? - is
> > it used ?
>
> a switch creates virtual circuits between two communicating devices rather
> than sending out to everyone.
>
> The PC sends it traffic to the destination... the switch takes that and
> imagine it making a pass thru connection from the source port to the
> destination port... no other ports on the switch see the traffic...
>
> unlike a hub that is 'dumb'..it gets traffic and shoots it out all
> ports...it knows nothing....
>
> imagine a hub like a PA Intercom system... everyone hears it...and only
> those that the message relates to pay attention.
>
> Imagine a switch like a telephone operator... it takes a caller and
> connects them to another person... no one else gets involved or hears it.
>
> ROUGH ANALOGY! grin
>
> >
> > If you use a Hub will you need to broadcast before each communication
> > attempt to recognise the port on the hub... ?
>
> No... a broadcast will occur if the PC does not have an ARP entry... it it
> does, no broadcast is needed...the data is sent on the wire... if a hub is
> used...all PCs will see it, but only the destination will take it.
> A switch will take it and send it out only the wire to the destination.
>
> >
> > How does a switch work with PC's to reduce network traffic?
>
> Creates virtual circuits that stop the traffic from flowing on all parts
of
> the medium.
>
> >
> > From what somebody else told me, when communicating via a Hub you
> > must broadcast each time to identify the destination computer
> > information, when using a switch, the switch stores this information
> > so it is not necessary
> > to broadcast... is this true? if so does the switch prevent the
> > broadcast by replying itself? Is this an ARP broadcast which it
> > prevents?
>
> No.. the above should explain why this is not true.
>
> >
> > Thanks again, Karim
> >
> > "Mark M. Reed" <mreed@reedassociates.com> wrote in message
> > news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
> >> in regards to your second question:
> >>
> >> Mac addresses are stored locally in ARP cache..yes... they remain
> >> there
> > for
> >> e predetermined timeframe then timeout if no communication is made to
> >> that host.
> >>
> >> When all the hosts start up..for example at a business at 8am...
> >> there are no arp entries... whenever comm needs to occur between a
> >> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
> >> each host on that physical media and they each examine it for a
> >> reply... if they are not X, they drop it ...X however responds.. I AM
> >> X. This response is what allows the requesting host to make an ARP
> >> entry.
> >>
> >> You mention a hub... remeber a hub is just a multiport
> > repeater..broadcasts
> >> flow thru a hub. It works basically the same way with a switch..but
> >> a switch will learn the MACs just like a host to build its switching
> >> tables.
> >>
> >> The switch does not have a table entry for MAC X... it sends it to
> >> all and waits for the owner to reply..it them makes its entry.
> >>
> >> You can also physically enter ARP mappings under the windows DOS CLI.
> >>
> >> Do an ARP /? and look at all the options.
> >>
> >> Another great way to visualize this is to download the sniffer
> >> ETHEREAL
> > and
> >> watch the packets on your network... you will see this process in
> >> realtime...that is very helpful. Do a search on ETHEREAL.. its a
> > shareware
> >> sniffer.
> >>
> >> Mark M. Reed
> >>
> >>
> >>
> >>
> >> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> >> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
> >>
> >> > My other question was about network communication, from
> >> > what I can gather, IP addresses are only required to resolve
> >> > MAC addresses and Hostnames and to cross over from one
> >> > lan to the other through a gateway. Actual communication
> >> > within a LAN uses MAC addresses which are stored in cache
> >> > on the individual computers so that each time communication
> >> > takes place it need not start with an ARP broadcast to reduce
> >> > network traffic... now if you connect devices using a hub -
> >> > everytime you begin communicating... will you not always have
> >> > to start with a broadcast? How will the computer know which
> >> > port the destination computer is connected to on the hub? If you
> >> > connect devices using a switch how is this different?
> >> >
> >> > ... As you can see I am totally lost and probably more confused
> >> > than I think I am!
> >> >
> >> > Please Advise!
> >> >
> >> > Thanking you in advance, Karim.
> >> >
> >> >
> >> >
> >>
> >>
> >
> >
> >
>
| |
| Karim M Ladhu 2002-08-28, 4:28 pm |
| Thanks alot Mark,
That really clears up my second question...
Kind Regards, Karim
Note: Now im only 1/2 as confused as before :-) ...and yes, I did
like your analogy!
"Mark M. Reed" <mreed@reedassociates.com> wrote in message
news:Xns9278A4E4882A5mreedreed
associatesc@216.168.3.40...
> See comments per line below:
>
>
> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
>
> > Thanks for your reply...
> >
> > If a switch has already learned the MAC addresses for each node
> > connected to each of its interfaces... how is this used by PC's ? - is
> > it used ?
>
> a switch creates virtual circuits between two communicating devices rather
> than sending out to everyone.
>
> The PC sends it traffic to the destination... the switch takes that and
> imagine it making a pass thru connection from the source port to the
> destination port... no other ports on the switch see the traffic...
>
> unlike a hub that is 'dumb'..it gets traffic and shoots it out all
> ports...it knows nothing....
>
> imagine a hub like a PA Intercom system... everyone hears it...and only
> those that the message relates to pay attention.
>
> Imagine a switch like a telephone operator... it takes a caller and
> connects them to another person... no one else gets involved or hears it.
>
> ROUGH ANALOGY! grin
>
> >
> > If you use a Hub will you need to broadcast before each communication
> > attempt to recognise the port on the hub... ?
>
> No... a broadcast will occur if the PC does not have an ARP entry... it it
> does, no broadcast is needed...the data is sent on the wire... if a hub is
> used...all PCs will see it, but only the destination will take it.
> A switch will take it and send it out only the wire to the destination.
>
> >
> > How does a switch work with PC's to reduce network traffic?
>
> Creates virtual circuits that stop the traffic from flowing on all parts
of
> the medium.
>
> >
> > From what somebody else told me, when communicating via a Hub you
> > must broadcast each time to identify the destination computer
> > information, when using a switch, the switch stores this information
> > so it is not necessary
> > to broadcast... is this true? if so does the switch prevent the
> > broadcast by replying itself? Is this an ARP broadcast which it
> > prevents?
>
> No.. the above should explain why this is not true.
>
> >
> > Thanks again, Karim
> >
> > "Mark M. Reed" <mreed@reedassociates.com> wrote in message
> > news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
> >> in regards to your second question:
> >>
> >> Mac addresses are stored locally in ARP cache..yes... they remain
> >> there
> > for
> >> e predetermined timeframe then timeout if no communication is made to
> >> that host.
> >>
> >> When all the hosts start up..for example at a business at 8am...
> >> there are no arp entries... whenever comm needs to occur between a
> >> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
> >> each host on that physical media and they each examine it for a
> >> reply... if they are not X, they drop it ...X however responds.. I AM
> >> X. This response is what allows the requesting host to make an ARP
> >> entry.
> >>
> >> You mention a hub... remeber a hub is just a multiport
> > repeater..broadcasts
> >> flow thru a hub. It works basically the same way with a switch..but
> >> a switch will learn the MACs just like a host to build its switching
> >> tables.
> >>
> >> The switch does not have a table entry for MAC X... it sends it to
> >> all and waits for the owner to reply..it them makes its entry.
> >>
> >> You can also physically enter ARP mappings under the windows DOS CLI.
> >>
> >> Do an ARP /? and look at all the options.
> >>
> >> Another great way to visualize this is to download the sniffer
> >> ETHEREAL
> > and
> >> watch the packets on your network... you will see this process in
> >> realtime...that is very helpful. Do a search on ETHEREAL.. its a
> > shareware
> >> sniffer.
> >>
> >> Mark M. Reed
> >>
> >>
> >>
> >>
> >> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
> >> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
> >>
> >> > My other question was about network communication, from
> >> > what I can gather, IP addresses are only required to resolve
> >> > MAC addresses and Hostnames and to cross over from one
> >> > lan to the other through a gateway. Actual communication
> >> > within a LAN uses MAC addresses which are stored in cache
> >> > on the individual computers so that each time communication
> >> > takes place it need not start with an ARP broadcast to reduce
> >> > network traffic... now if you connect devices using a hub -
> >> > everytime you begin communicating... will you not always have
> >> > to start with a broadcast? How will the computer know which
> >> > port the destination computer is connected to on the hub? If you
> >> > connect devices using a switch how is this different?
> >> >
> >> > ... As you can see I am totally lost and probably more confused
> >> > than I think I am!
> >> >
> >> > Please Advise!
> >> >
> >> > Thanking you in advance, Karim.
> >> >
> >> >
> >> >
> >>
> >>
> >
> >
> >
>
| |
| Colin Bailey 2002-08-28, 4:28 pm |
| On Wed, 28 Aug 2002 20:54:06 GMT, "Karim M Ladhu"
<contactme@karimladhu.co.uk> wrote:
Another point to note:
Switch as described here , Layer 2.
Hub, layer 1, as good as purely electrical repetition.
Don`t think a switch a like a more complex hub, it isn`t and it can
get confusing if you think of it that away.
The analogy of PA vs Telephone is a good one, yet don`t think they are
in anyway the same. They are very very different and shouldn`t be
considered similar at all.
You are best grouping switches/bridges and routers
and keeping hubs totally separate in your thought process.
Think hub, think electrical. Think no protocol understanding at all,
think purely electrical repetition/amplification.
>Thanks alot Mark,
>
>That really clears up my second question...
>
>Kind Regards, Karim
>
>Note: Now im only 1/2 as confused as before :-) ...and yes, I did
> like your analogy!
>
>"Mark M. Reed" <mreed@reedassociates.com> wrote in message
> news:Xns9278A4E4882A5mreedreed
associatesc@216.168.3.40...
>> See comments per line below:
>>
>>
>> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
>>
>> > Thanks for your reply...
>> >
>> > If a switch has already learned the MAC addresses for each node
>> > connected to each of its interfaces... how is this used by PC's ? - is
>> > it used ?
>>
>> a switch creates virtual circuits between two communicating devices rather
>> than sending out to everyone.
>>
>> The PC sends it traffic to the destination... the switch takes that and
>> imagine it making a pass thru connection from the source port to the
>> destination port... no other ports on the switch see the traffic...
>>
>> unlike a hub that is 'dumb'..it gets traffic and shoots it out all
>> ports...it knows nothing....
>>
>> imagine a hub like a PA Intercom system... everyone hears it...and only
>> those that the message relates to pay attention.
>>
>> Imagine a switch like a telephone operator... it takes a caller and
>> connects them to another person... no one else gets involved or hears it.
>>
>> ROUGH ANALOGY! grin
>>
>> >
>> > If you use a Hub will you need to broadcast before each communication
>> > attempt to recognise the port on the hub... ?
>>
>> No... a broadcast will occur if the PC does not have an ARP entry... it it
>> does, no broadcast is needed...the data is sent on the wire... if a hub is
>> used...all PCs will see it, but only the destination will take it.
>> A switch will take it and send it out only the wire to the destination.
>>
>> >
>> > How does a switch work with PC's to reduce network traffic?
>>
>> Creates virtual circuits that stop the traffic from flowing on all parts
>of
>> the medium.
>>
>> >
>> > From what somebody else told me, when communicating via a Hub you
>> > must broadcast each time to identify the destination computer
>> > information, when using a switch, the switch stores this information
>> > so it is not necessary
>> > to broadcast... is this true? if so does the switch prevent the
>> > broadcast by replying itself? Is this an ARP broadcast which it
>> > prevents?
>>
>> No.. the above should explain why this is not true.
>>
>> >
>> > Thanks again, Karim
>> >
>> > "Mark M. Reed" <mreed@reedassociates.com> wrote in message
>> > news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
>> >> in regards to your second question:
>> >>
>> >> Mac addresses are stored locally in ARP cache..yes... they remain
>> >> there
>> > for
>> >> e predetermined timeframe then timeout if no communication is made to
>> >> that host.
>> >>
>> >> When all the hosts start up..for example at a business at 8am...
>> >> there are no arp entries... whenever comm needs to occur between a
>> >> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
>> >> each host on that physical media and they each examine it for a
>> >> reply... if they are not X, they drop it ...X however responds.. I AM
>> >> X. This response is what allows the requesting host to make an ARP
>> >> entry.
>> >>
>> >> You mention a hub... remeber a hub is just a multiport
>> > repeater..broadcasts
>> >> flow thru a hub. It works basically the same way with a switch..but
>> >> a switch will learn the MACs just like a host to build its switching
>> >> tables.
>> >>
>> >> The switch does not have a table entry for MAC X... it sends it to
>> >> all and waits for the owner to reply..it them makes its entry.
>> >>
>> >> You can also physically enter ARP mappings under the windows DOS CLI.
>> >>
>> >> Do an ARP /? and look at all the options.
>> >>
>> >> Another great way to visualize this is to download the sniffer
>> >> ETHEREAL
>> > and
>> >> watch the packets on your network... you will see this process in
>> >> realtime...that is very helpful. Do a search on ETHEREAL.. its a
>> > shareware
>> >> sniffer.
>> >>
>> >> Mark M. Reed
>> >>
>> >>
>> >>
>> >>
>> >> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> >> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>> >>
>> >> > My other question was about network communication, from
>> >> > what I can gather, IP addresses are only required to resolve
>> >> > MAC addresses and Hostnames and to cross over from one
>> >> > lan to the other through a gateway. Actual communication
>> >> > within a LAN uses MAC addresses which are stored in cache
>> >> > on the individual computers so that each time communication
>> >> > takes place it need not start with an ARP broadcast to reduce
>> >> > network traffic... now if you connect devices using a hub -
>> >> > everytime you begin communicating... will you not always have
>> >> > to start with a broadcast? How will the computer know which
>> >> > port the destination computer is connected to on the hub? If you
>> >> > connect devices using a switch how is this different?
>> >> >
>> >> > ... As you can see I am totally lost and probably more confused
>> >> > than I think I am!
>> >> >
>> >> > Please Advise!
>> >> >
>> >> > Thanking you in advance, Karim.
>> >> >
>> >> >
>> >> >
>> >>
>> >>
>> >
>> >
>> >
>>
>
---------------------
Colin Bailey
colin@sysol.demon.co.uk
MS messenger account - colinbailey_uk@hotmail.com
Mobile: 07XXX XXXXXX
| |
| Colin Bailey 2002-08-28, 5:28 pm |
| On Wed, 28 Aug 2002 20:54:06 GMT, "Karim M Ladhu"
<contactme@karimladhu.co.uk> wrote:
Another point to note:
Switch as described here , Layer 2.
Hub, layer 1, as good as purely electrical repetition.
Don`t think a switch a like a more complex hub, it isn`t and it can
get confusing if you think of it that away.
The analogy of PA vs Telephone is a good one, yet don`t think they are
in anyway the same. They are very very different and shouldn`t be
considered similar at all.
You are best grouping switches/bridges and routers
and keeping hubs totally separate in your thought process.
Think hub, think electrical. Think no protocol understanding at all,
think purely electrical repetition/amplification.
>Thanks alot Mark,
>
>That really clears up my second question...
>
>Kind Regards, Karim
>
>Note: Now im only 1/2 as confused as before :-) ...and yes, I did
> like your analogy!
>
>"Mark M. Reed" <mreed@reedassociates.com> wrote in message
> news:Xns9278A4E4882A5mreedreed
associatesc@216.168.3.40...
>> See comments per line below:
>>
>>
>> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> news:iu9b9.144061$Aw4.5976257@bin2.nnrp.aus1.giganews.com:
>>
>> > Thanks for your reply...
>> >
>> > If a switch has already learned the MAC addresses for each node
>> > connected to each of its interfaces... how is this used by PC's ? - is
>> > it used ?
>>
>> a switch creates virtual circuits between two communicating devices rather
>> than sending out to everyone.
>>
>> The PC sends it traffic to the destination... the switch takes that and
>> imagine it making a pass thru connection from the source port to the
>> destination port... no other ports on the switch see the traffic...
>>
>> unlike a hub that is 'dumb'..it gets traffic and shoots it out all
>> ports...it knows nothing....
>>
>> imagine a hub like a PA Intercom system... everyone hears it...and only
>> those that the message relates to pay attention.
>>
>> Imagine a switch like a telephone operator... it takes a caller and
>> connects them to another person... no one else gets involved or hears it.
>>
>> ROUGH ANALOGY! grin
>>
>> >
>> > If you use a Hub will you need to broadcast before each communication
>> > attempt to recognise the port on the hub... ?
>>
>> No... a broadcast will occur if the PC does not have an ARP entry... it it
>> does, no broadcast is needed...the data is sent on the wire... if a hub is
>> used...all PCs will see it, but only the destination will take it.
>> A switch will take it and send it out only the wire to the destination.
>>
>> >
>> > How does a switch work with PC's to reduce network traffic?
>>
>> Creates virtual circuits that stop the traffic from flowing on all parts
>of
>> the medium.
>>
>> >
>> > From what somebody else told me, when communicating via a Hub you
>> > must broadcast each time to identify the destination computer
>> > information, when using a switch, the switch stores this information
>> > so it is not necessary
>> > to broadcast... is this true? if so does the switch prevent the
>> > broadcast by replying itself? Is this an ARP broadcast which it
>> > prevents?
>>
>> No.. the above should explain why this is not true.
>>
>> >
>> > Thanks again, Karim
>> >
>> > "Mark M. Reed" <mreed@reedassociates.com> wrote in message
>> > news:Xns927899A7256BDmreedreed
associatesc@216.168.3.40...
>> >> in regards to your second question:
>> >>
>> >> Mac addresses are stored locally in ARP cache..yes... they remain
>> >> there
>> > for
>> >> e predetermined timeframe then timeout if no communication is made to
>> >> that host.
>> >>
>> >> When all the hosts start up..for example at a business at 8am...
>> >> there are no arp entries... whenever comm needs to occur between a
>> >> host, an ARP broadcast is made... WHO HAS (X)? it is picked up by
>> >> each host on that physical media and they each examine it for a
>> >> reply... if they are not X, they drop it ...X however responds.. I AM
>> >> X. This response is what allows the requesting host to make an ARP
>> >> entry.
>> >>
>> >> You mention a hub... remeber a hub is just a multiport
>> > repeater..broadcasts
>> >> flow thru a hub. It works basically the same way with a switch..but
>> >> a switch will learn the MACs just like a host to build its switching
>> >> tables.
>> >>
>> >> The switch does not have a table entry for MAC X... it sends it to
>> >> all and waits for the owner to reply..it them makes its entry.
>> >>
>> >> You can also physically enter ARP mappings under the windows DOS CLI.
>> >>
>> >> Do an ARP /? and look at all the options.
>> >>
>> >> Another great way to visualize this is to download the sniffer
>> >> ETHEREAL
>> > and
>> >> watch the packets on your network... you will see this process in
>> >> realtime...that is very helpful. Do a search on ETHEREAL.. its a
>> > shareware
>> >> sniffer.
>> >>
>> >> Mark M. Reed
>> >>
>> >>
>> >>
>> >>
>> >> "Karim M Ladhu" <contactme@karimladhu.co.uk> wrote in
>> >> news:6T8b9.270954$2p2.10842291@bin4.nnrp.aus1.giganews.com:
>> >>
>> >> > My other question was about network communication, from
>> >> > what I can gather, IP addresses are only required to resolve
>> >> > MAC addresses and Hostnames and to cross over from one
>> >> > lan to the other through a gateway. Actual communication
>> >> > within a LAN uses MAC addresses which are stored in cache
>> >> > on the individual computers so that each time communication
>> >> > takes place it need not start with an ARP broadcast to reduce
>> >> > network traffic... now if you connect devices using a hub -
>> >> > everytime you begin communicating... will you not always have
>> >> > to start with a broadcast? How will the computer know which
>> >> > port the destination computer is connected to on the hub? If you
>> >> > connect devices using a switch how is this different?
>> >> >
>> >> > ... As you can see I am totally lost and probably more confused
>> >> > than I think I am!
>> >> >
>> >> > Please Advise!
>> >> >
>> >> > Thanking you in advance, Karim.
>> >> >
>> >> >
>> >> >
>> >>
>> >>
>> >
>> >
>> >
>>
>
---------------------
Colin Bailey
colin@sysol.demon.co.uk
MS messenger account - colinbailey_uk@hotmail.com
Mobile: 07XXX XXXXXX
|
|
|
|
|