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upgrading-lan

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Anonymous
March 3, 2005 5:14:14 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello,

I need some quick advice on upgrading our lan as I am a bit unsure on
a couple of things. We are intending to buy netgear 4 24 10/100
switches and 2 24 gbit port switches to replace our old ones. The
switches I believe all have stack ports and 2 2gbit uplink ports and
was told I can stack up to 4 of them.

I have a couple of questions

1) Someone was suggesting not to use the stack ports but just connect
the gbit ports from the 4 10/100 switches to the gbit switches. I am a
bit wary of this and I think this could cause bottleneck - I am
correct? If 10 machines were trying to talk thorugh the gbit port to
the other switches then wouldnt that saturate the link? - whereas if
you used the stackable ports to interconnect the switches this would
not happen?

2) If you do 'stack the switches' then isnt there a redundancy problem
in that in effect the stack ports are daisy chained so if the middle
switch broke this would affect communication between switch 1 and
switch 4? So for redundancy if you elimetaed the stack method but
connecting each switch to the gbit backplane switch, if one of the
10/100 switches died - it would not affect any of the others?


Thanks for any advice.

More about : upgrading lan

Anonymous
March 4, 2005 3:00:42 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <9607ea95.0503031414.79b0d65e@posting.google.com>,
chris-c <cconnell_1@lycos.com> wrote:
:I need some quick advice on upgrading our lan as I am a bit unsure on
:a couple of things. We are intending to buy netgear 4 24 10/100
:switches and 2 24 gbit port switches to replace our old ones.

If you intend these to be high utilization devices, then it would be
a good idea to buy 1 first and stress test it in your environment.
Different Netgear switch models have different quality levels.
The further you get from Netgear's traditional consumer-level device,
the more caution is advised.

:1) Someone was suggesting not to use the stack ports but just connect
:the gbit ports from the 4 10/100 switches to the gbit switches. I am a
:bit wary of this and I think this could cause bottleneck - I am
:correct? If 10 machines were trying to talk thorugh the gbit port to
:the other switches then wouldnt that saturate the link? - whereas if
:you used the stackable ports to interconnect the switches this would
:not happen?

Switches that are directly stacked will use the local stacking bus
to exchange data. The speed of that will depend upon the speed of
the stacking bus and upon how it is used [some stacks are sychronous,
alloting time for each stacked device in turn, even if they have
nothing to say!].

If you have two switches without uplink ports that could stack together
but you connect them by way of a different switch, then the latency
will be the latency of serializing the data out of switch 1, receiving
it and switching it in the core switch, serializing it out of the
core switch, and receiving it in the destination switch; the maximum
throughput for this operation will be the minimum of speed of the
links involved. In the case of the 24-port 10/100 switches, that's
going to be a maximum throughput rate of 100 Mbit/s, with
latency of two switches serializing for transmission and two switches
receiving transmission and one switch switching between ports; add
a tinsy bit for the actual wire speed between the devices.

If you stack the two switches together instead, then the latency would
be the latency of serializing to the parallel shared bus, and of
receiving at the other end of the parallel shared bus, plus an
itsy bitsy teeny weeny time for transmission over the 1 metre bus cable.
Throughput would be whatever the rate the bus ran at, taking into
account parallel transmission rather than serial (e.g., 100 MHz of
parallel 8-bit data is equivilent to 800 MHz of bit-at-a-time serial data.)

Stacking busses are usually noticably faster than the fastest port.
For example, on the 24 port 10/1000 switch, the stacking bus might
run at 1 Gbit/s.


:2) If you do 'stack the switches' then isnt there a redundancy problem
:in that in effect the stack ports are daisy chained so if the middle
:switch broke this would affect communication between switch 1 and
:switch 4? So for redundancy if you elimetaed the stack method but
:connecting each switch to the gbit backplane switch, if one of the
:10/100 switches died - it would not affect any of the others?

It depends on how the manufacturer impliments stacking. Nortel and
Cisco use ring topologies (last device is connected to the first) so
there is always a way to get to a device if something in the middle
breaks. The better switches automatically manage around failures.
For example, Cisco's new "StackWise Technology" is fully able to have
a new switch step in quickly as the new master if the master switch fails.

In the star topology you haven't eliminated single points of failure:
you've just made the gigabit switch your single point of failure.
Considering that gigabit is newer technology that hasn't had as much
time to smoke out the bugs, you could be -reducing- your reliability
by going star topology instead of stacking well-developed 10/100 switches.
--
Suppose there was a test you could take that would report whether
you had Free Will or were Pre-Destined. Would you take the test?
March 4, 2005 11:32:44 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"chris-c" <cconnell_1@lycos.com> wrote in message
news:9607ea95.0503031414.79b0d65e@posting.google.com...
> Hello,
>
> I need some quick advice on upgrading our lan as I am a bit unsure on
> a couple of things. We are intending to buy netgear 4 24 10/100
> switches and 2 24 gbit port switches to replace our old ones. The
> switches I believe all have stack ports and 2 2gbit uplink ports and
> was told I can stack up to 4 of them.

nortel stacking used to support more than 4 devices so i am not sure if this
is correct - but you dont specify which switches.

also, nortel tend to have several models that can be in the same stack.

the golden rule is to work with accurate info. i suggest you look at the web
site and work out what the boxes can do: http://www.nortelnetworks.com/
>
> I have a couple of questions
>
> 1) Someone was suggesting not to use the stack ports but just connect
> the gbit ports from the 4 10/100 switches to the gbit switches. I am a
> bit wary of this and I think this could cause bottleneck - I am
> correct? If 10 machines were trying to talk thorugh the gbit port to
> the other switches then wouldnt that saturate the link? - whereas if
> you used the stackable ports to interconnect the switches this would
> not happen?

depends on the aggregate traffic. If your network only has 1 or 2 main
servers connected at Gigabit speeds, then the servers will form the
practical limit to throughput rather than the switch ports no matter how you
interconnect the switches.

if the switches have built in stacking, then stack cables are probably
cheaper than GBICs (assuming they dont come with the switches as standard
anyway).

Stacking has always been designed to be faster than Gigabit - high capacity
between the switches is one of the major selling points.
>
> 2) If you do 'stack the switches' then isnt there a redundancy problem
> in that in effect the stack ports are daisy chained so if the middle
> switch broke this would affect communication between switch 1 and
> switch 4? So for redundancy if you elimetaed the stack method but
> connecting each switch to the gbit backplane switch, if one of the
> 10/100 switches died - it would not affect any of the others?

nortel stacks usually support a "ring" of stack cables - the idea is you can
loose a cable or a switch, and the rest of the stack isnt affected.

the main drawback to stacking is that the switches in the stack end up very
closely linked, so there may be sortware version constraints, and the risk
of a software bug affecting the stack is probably greater than if you just
linked devices together via Gigabit - the switches in the stack are
logically more like blades in a chassis than standalone boxes.

having said that nortel have been stacking switches for a long time, and it
has worked well for me.
>
>
> Thanks for any advice.
--
Regards

Stephen Hope - return address needs fewer xxs
Anonymous
March 7, 2005 2:36:21 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

chris-c wrote:
> Hello,
>
> I need some quick advice on upgrading our lan as I am a bit unsure on
> a couple of things. We are intending to buy netgear 4 24 10/100
> switches and 2 24 gbit port switches to replace our old ones. The
> switches I believe all have stack ports and 2 2gbit uplink ports and
> was told I can stack up to 4 of them.
>
> I have a couple of questions
>
> 1) Someone was suggesting not to use the stack ports but just connect
> the gbit ports from the 4 10/100 switches to the gbit switches. I am a
> bit wary of this and I think this could cause bottleneck - I am
> correct? If 10 machines were trying to talk thorugh the gbit port to
> the other switches then wouldnt that saturate the link? - whereas if
> you used the stackable ports to interconnect the switches this would
> not happen?

Definitely connect the gig ports on the 10/100 switches to the gig
switch directly. You'll get much better overall bandwidth - think about
it - if you stack them and then run from just one gig port, you only
have 1/4 the bandwidth going to the gig switch.

>
> 2) If you do 'stack the switches' then isnt there a redundancy problem
> in that in effect the stack ports are daisy chained so if the middle
> switch broke this would affect communication between switch 1 and
> switch 4? So for redundancy if you elimetaed the stack method but
> connecting each switch to the gbit backplane switch, if one of the
> 10/100 switches died - it would not affect any of the others?
>

Yes. The way netgear stacks, yes. Other switches can stack in a ring -
top and bottom of stack connect - so they are tolerant of a link failure
in the stack. But not netgear.
>
> Thanks for any advice.


MY biggest suggestion, after sturggling to get netgear switches to work
as advertised over the last year and a half, is AVOID NETGEAR HIGH END
SWITCHES AT ALL COST.

I have had VERY bad luck with the following:

GSM712, FSM726s - bad handling of multicats packets - very easy to lock
up a port with multicast traffic.

GSM7312-GSM7324 - The ospf implementaion is so bug ridden as to be
almost completely unusable.
Anonymous
March 8, 2005 10:43:24 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"T. Sean Weintz" <strap@hanh-ct.org> wrote in message news:<112p0o65vlp0560@news.supernews.com>...
> chris-c wrote:
> > Hello,
> >
> > I need some quick advice on upgrading our lan as I am a bit unsure on
> > a couple of things. We are intending to buy netgear 4 24 10/100
> > switches and 2 24 gbit port switches to replace our old ones. The
> > switches I believe all have stack ports and 2 2gbit uplink ports and
> > was told I can stack up to 4 of them.
> >
> > I have a couple of questions
> >
> > 1) Someone was suggesting not to use the stack ports but just connect
> > the gbit ports from the 4 10/100 switches to the gbit switches. I am a
> > bit wary of this and I think this could cause bottleneck - I am
> > correct? If 10 machines were trying to talk thorugh the gbit port to
> > the other switches then wouldnt that saturate the link? - whereas if
> > you used the stackable ports to interconnect the switches this would
> > not happen?
>
> Definitely connect the gig ports on the 10/100 switches to the gig
> switch directly. You'll get much better overall bandwidth - think about
> it - if you stack them and then run from just one gig port, you only
> have 1/4 the bandwidth going to the gig switch.
>
> >
> > 2) If you do 'stack the switches' then isnt there a redundancy problem
> > in that in effect the stack ports are daisy chained so if the middle
> > switch broke this would affect communication between switch 1 and
> > switch 4? So for redundancy if you elimetaed the stack method but
> > connecting each switch to the gbit backplane switch, if one of the
> > 10/100 switches died - it would not affect any of the others?
> >
>
> Yes. The way netgear stacks, yes. Other switches can stack in a ring -
> top and bottom of stack connect - so they are tolerant of a link failure
> in the stack. But not netgear.
> >
> > Thanks for any advice.
>
>
> MY biggest suggestion, after sturggling to get netgear switches to work
> as advertised over the last year and a half, is AVOID NETGEAR HIGH END
> SWITCHES AT ALL COST.
>
> I have had VERY bad luck with the following:
>
> GSM712, FSM726s - bad handling of multicats packets - very easy to lock
> up a port with multicast traffic.
>
> GSM7312-GSM7324 - The ospf implementaion is so bug ridden as to be
> almost completely unusable.


Thanks for all the help here.

We looked at 3COM stacking solution but I find with 3COM switches you
need to buy every single module e.g. stack kits, gb cards, which is
not so straight forward.

We had quite a good solution from HP which looked as follows 2 pairs
of switches connected to 2 GB switches. The servers would be on the GB
SWITCH1 and the clients on the 10/100 switch.

switcha(10/100) GB1 GB2
| | Trunked 2GB to GB switch1 --2GB---> GB
SWITCH1
switchb(10/100) GB1 GB2 |-----------^ |
| |8GB
TRUNK
switchc(10/100) GB1 GB2 | |
| | Trunked 2GB to GB switch1 GB
SWITCH2
switchd(10/100) GB1 GB2

The GB SWITCH2 would act as a cold failover.

Has anyone had any experience with HP switches? ie any good/bad
references?

Thanks
Anonymous
March 8, 2005 4:03:17 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

chris-c wrote:

>
> Thanks for all the help here.
>
> We looked at 3COM stacking solution but I find with 3COM switches you
> need to buy every single module e.g. stack kits, gb cards, which is
> not so straight forward.
>
> We had quite a good solution from HP which looked as follows 2 pairs
> of switches connected to 2 GB switches. The servers would be on the GB
> SWITCH1 and the clients on the 10/100 switch.
>
> switcha(10/100) GB1 GB2
> | | Trunked 2GB to GB switch1 --2GB---> GB
> SWITCH1
> switchb(10/100) GB1 GB2 |-----------^ |
> | |8GB
> TRUNK
> switchc(10/100) GB1 GB2 | |
> | | Trunked 2GB to GB switch1 GB
> SWITCH2
> switchd(10/100) GB1 GB2
>
> The GB SWITCH2 would act as a cold failover.
>
> Has anyone had any experience with HP switches? ie any good/bad
> references?
>
> Thanks

As you can see from above, your ascii diagram got clobbered upon
posting, or at least I THINK it did -- either way I cannot make sense of it.

Whay HP model switches are you looking at? The one thing I can about
switches is if you buy cheap stuff, you always get what you pay for (ie:
cheaply made equipment)

I have heard good things about some of the HP switches.
I have also heard mostly only good about Extreme. I have used Nortel
quite a lt and had good luck with them.

But you can't really do it by brand - you need to look at each specific
model seperately.
Anonymous
March 8, 2005 9:14:01 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <9607ea95.0503080743.5964c2a2@posting.google.com>,
cconnell_1@lycos.com (chris-c) writes:
>
>We looked at 3COM stacking solution but I find with 3COM switches you
>need to buy every single module e.g. stack kits, gb cards, which is
>not so straight forward.
>
>We had quite a good solution from HP which looked as follows 2 pairs
>of switches connected to 2 GB switches. The servers would be on the GB
>SWITCH1 and the clients on the 10/100 switch.
>
>switcha(10/100) GB1 GB2
> | | Trunked 2GB to GB switch1 --2GB---> GB
>SWITCH1
>switchb(10/100) GB1 GB2 |-----------^ |
> | |8GB
>TRUNK
>switchc(10/100) GB1 GB2 | |
> | | Trunked 2GB to GB switch1 GB
>SWITCH2
>switchd(10/100) GB1 GB2
>
>The GB SWITCH2 would act as a cold failover.
>
>Has anyone had any experience with HP switches? ie any good/bad
>references?

The current series are not as outstandanding as the 4000M series
where back then but we still buy them for their lifetime warranty.
Personally, I try to avoid stacks in one rack for management,
performance and reliability reasons. Even if it is not the
cheapest solution, I would go for a chassis switch. With HP
I would buy the bundles, put the modules and the power supplies
in one chassis and even have a cold failover chassis.

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de
!