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Connecting Cisco 3548XL and Cisco 3750 Switches

Hi there.

I have a Cisco Catalyst 3548XL Switch that connects all of network devices (client PCs, router, printers, etc). I'm adding a Cisco 3750 24-Port switch to add more capacity and add Power over Ethernet (PoE) capability. I wanted to check on how I should go about connecting these two switches so that all devices, no matter which switch they're connected to, can talk to each other.

Is it as easy as taking a cross over cable and connecting 1 port on the 3548 to the 3750?

Your input is appreciated.


Avatar of pjtemplin

Do you have more than one VLAN?  How much traffic do you have?

If nothing else, you'll want to set the ports up as trunk ports, so you can expand to VLANs even if you aren't already using them.

int f0/24
 speed 100
 duplex full
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 2
 switchport mode trunk

I would also recommend building it as a FastEtherChannel so you can increase the bandwidth between switches.  Put "channel-group 1" on the port configuration, then add the switchport commands above to interface port-channel 1.
Avatar of brownmetals


Thanks for the reply.

I have about 30 users, most of which is email, internet, and PDF attachment traffic. VLAN I assume means Virtual Lan and I'm not familiar with those. What's the advantage of setting up a VLAN?

I've programed a Cisco router before, so the code you've given me I'm sure I can copy and paste into the console as I've done with the router. Can you explain a little bit more about "trunk ports" as they relate to VLANs and this code?

As far as the last comment is concerned, I'm not familiar enough with Cisco equipment to understand what that suggestion means or how it should be implemented. Can you provide further detail on that?

Thank you,

Avatar of pjtemplin

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So if I understand that correctly, at a minimum, I should setup an EtherChannel. Is that correct? If so, can you walk me through the steps on doing that? I imagine it has to do with the config code in the 1st posting, but I'd like to have a better understanding of what that code means.


Putting "channel-group 1" in the first port's config assigns the port to that channel group.  It also creates a new virtual interface, port-channel 1.  Unfortunately, each switch series seems to handle channels differently, so you'll want to check the documentation to be specific (and I can't find docs on the 3548XL), but you'll probably want to apply all changes to the port-channel interface and each member interface.  You may just have to experiment.

By default, the switches will negotiate actual channeling over the requested ports, so it should protect you from mismatches.