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Cat 3550 Switch GBIC connection question

Unanswered Question
Jun 19th, 2006
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I was wondering if you can connect a Cat 3550 GBIC port(using ws-g5483) to a CAT 3750 10/100/1000 port as a trunk port. I have tried this setup, but it seems that there may be a speed/duplex issue. I never get a link light between the 3550 GBIC and the 3750, but do get connectivity between the same 3550 GBIC and a 2950 10/100/1000 port. Both the 3550 and the 3750 are set to auto negotiate the port speed.

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vladrac-ccna Mon, 06/19/2006 - 12:08
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this is from cisco cat3550:

"You can configure interface speed on Fast Ethernet (10/100-Mbps) and Gigabit Ethernet (10/100/1000-Mbps) interfaces; you cannot configure speed on Gigabit Interface Converter (GBIC) interfaces. You can configure duplex mode on any Fast Ethernet or Gigabit Ethernet interfaces that are not set to autonegotiate; you cannot configure duplex mode on GBIC interfaces.




DJCanuck1_2 Tue, 06/20/2006 - 10:47
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This still does not explain why the GBIC, which runs at 1000 MB by default (auto-negotiation) does not link up with a 10/100/1000 ethernet port which is set to aut-negotiate. Does the GBIC have to communicate with another GBIC?

jstoecker Thu, 06/22/2006 - 13:58
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You might try seeing what flow-control is set on both ends. To get a cat5000 supe with 5484 GBICs to work with a Dell switch with 5484 GBICs, and a 2950T (UTP 10/100/1000) to work with the Dell with a cisco 5483 1000BaseT gbic, I ended up having to play with these until the link would work.

e.g. try on both ends

conf t

int gi#/#

flowcontrol receive off

flowcontrol send off

(or whatever)

Also (you probably have checked this, but in case you haven't - and if this works with the 2950 I can't imagine why it wouldn't work with the 3550) verify you have all four pairs in your crossover cable correct -

1, 2 to 3, 6;

3, 6 to 1, 2;

4, 5 to 7, 8,

7, 8 to 4, 5



Roberto Salazar Thu, 06/22/2006 - 16:37
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Hi, 2950 and 3750 have different ASIC, so the behavior might not be the same. However, this sounds like the link negotiation issue, have you tried the following on the 3750:

speed nonegotiate

This should bring the link up.

Please rate all posts.


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