Connecting 2 2950G's via Fibre GBICs

Hi there - this may seem a silly question.... I have a 4507R Core Swich conncted to several 2950G Switches. We need to add in a another office location that is already connected to the distribution rack (where the 2950's are) by fibre and I was hoping I could use the second GBIC port on the 2950 to connect to a new 2950G GBIC in the new office location.

That is - the 2950G in the distribution rack will have 2 GBIC's connected - 1 to the core switch and 1 to the down stream 2950G. Is there anything special about these ports being always referred to as UPLINK ports? I have done something similar in connecting 1 2950G to another 2950 but using ethernet on a standard port - it is just that this office is conencted by fibre.

We are looking at replacing some legacy 3Com gear running on 100Mb fibre that is already in place - hence we do not want to run new Cat5e cable.

Cheers Craig

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The arrangement you propose should be fine.

Reply to
Walter Roberson

switchport mode trunk should do the trick

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More context would be appreciated...

It has been awhile since I looked at the 2950; isn't it one of the models in which ports are usually autodetect as to whether they are trunks or not? If so then just connecting the two 2950 without any special configuration would work.

Moreover: trunk mode is for VLANs, and I don't recall the OP mentioning any VLAN use.

Reply to
Walter Roberson

I strongly beleve that all of the ports on the 2950 are ceated equal other than of course the raw port speed.

As far as I can recall Cisco have never used the term uplink to indicate a port that has poorer capabilities than another port. Indeed on for example the 4500 the SE located 'uplink' ports are superior to other ports in that they have a dedicated 1G into the fabric.

IIRC some other manufacturers do use or have used the term 'uplink' to indicate an inferior or limited port.

As Walter and others say, this is the designed use for the port, go ahead.

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uplink just means that it connectc to the network, as oppose to clients. normally uplink ports are also trunk-ports, and de facto Cisco switches will negotiate this, if a switchport sees another switchport. But best practice is to set the parameters of yout trunks manually.

You can use the command "show interface status" to see which ports are trunks.

If you are not using VLANs, you will not benefit much from trunkports. There is nothing "wrong" in doing a flat vlan all over, aslong as you switch diameter isnt to wide.

HTH Martin Bilgrav

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Martin Bilgrav

Hi Craig and Wally,

the 4507R and 2950G use the GBIC (like 5484 5486 ) that is Giga only , If you want to connection with 3Com switch , you must use the 1.25G GBIC or SFP .

if you want to use the 100M FX , you can choose the Cisco 3750G or some SFP connect , they provide the Giga or 155M(100M) solutions ..

1000 can not work with 100 fiber , the speed and nego will be problem ,

Ryan Ho Form Optech ...

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GBIC /SFP provider .....

if you have any question please contact with me .

wally =E5=AF=AB=E9=81=93=EF=BC=9A

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In article , OPTECH_GBIC top-posted:

The OP did not want to connect to the 3Com switch; the 3Com switch was being replaced.

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The Cisco 1000BASE-SX GBIC (WS-G5484) operates on ordinary multimode fiber (MMF) optic link spans up to 1815 feet (550 m) long.

And if you look further down to Table 1, you will see the 1000Base-SX rated for 62.5 micron and 50 micron MMF. The 1000Base-LX/LH is also rated for 62.5 and 50 micron MMF

The SFP datasheets,

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show 100FX on MMF at 1310 nm which is the same wavelength used by the 1000Base-LX/LH.

Therefore if you are already running 100FX on MMF, then you cannot have any wavelength or distance problems in using the 1000Base-LX/LH.

And since fibre pairs have no intelligence, as long as you have the same kind of interface on both sides of the fibre, you would be good to go. Fibre doesn't care how much phase information or whatever you are extracting from the signal. There is no such thing as "100 fiber" or "1000 fiber".

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Walter Roberson

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Yes, but different distances are achievable depending on the type and quality of the fibre. 550m is only possible with 50 micron fibre; with

62.5 you may be stuck at 220m.

But ONLY with the mode conditioning patch cord - can't just plug a standard MMF patch cord into an LX/LH GBIC or SFP and expect to get 550m transmission.

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Completely untrue. 100baseFX over MMF can hit 2km with no problem. You simply can't do that with 1000baseSX or 1000baseLX on MMF. The fact that you are successfully running 100baseFX on given fibre run doesn't mean that you can therefore run any flavour of GigE over it.

Whilst that's strictly true it probably doesn't help the discussion - there are different types of fibre which can be driven in different ways by different technologies. You have to know the characteristics of each.

Sam Wilson Network Development Team, Infrastructure Services Division Computing Services, The University of Edinburgh Edinburgh, Scotland, UK

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