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Routed port Vs Trunk port

jskfan
jskfan used Ask the Experts™
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on switch 3550, we can create vlans and SVI and use the IP routing command to enable the vlans to talk to each other without connecting the switch to the router.

What I need to understand is :
1- when connecting the 3550 switch to another L3 or L2 switch, would the connecting ports be configured as Trunk ports
2-when the 3550 swithc is connected to a Router, would the switch connecting port be configured as trunk port or we need to use No Switchport command. ?
what is the difference?

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When we have to get more than 1 VLAN information passed from the port we configure it as Trunk port. so incase of switch to switch connection we put Trunk port so that all VLAN information is passed.
Access port is just confined to one single VLAN. so normally when you connect a system to switch that port is configured as Access port as it will only take one VLAN information.
TimotiStDatacenter Technician
Top Expert 2012
Commented:
If you use a "routed port" with the "no switchport" command, it becomes like a port on a router: no vlans, no layer 2 protocols (lacp, stp, vtp, dtp). You can assign an IP address to it, and start routing.

On switchports, you can have one or more vlans, which can have SVIs as layer3 interfaces. Switchports will run typical switch protocols, like lacp, stp, vtp and dtp.

For example, on HP switches, there are no "routed ports". You get the (almost) same functionality by creating an otherwise unused vlan, assign that vlan as the access vlan to a port, and create an SVI interface for the vlan.

Tamas

Author

Commented:
If I understand when you connect L3 switch to a router you use No switchport command on the L3 switch port
Trunk port is used between L2 switch to L2 switch
When connecting L3 to L3 switch, I am not sure what to use?
TimotiStDatacenter Technician
Top Expert 2012
Commented:
Not necessarily. You can use whatever suits your needs.
L2switch-L2 switch usually uses trunk or sometimes access ports.

L3switch-L3switch can use trunk or routed ports, depending on your needs (basically if you want to switch, or route).

L3switch-router usually uses access or routed port.

For example, the standard Cisco 3 layer campus network model uses routed ports between core layer switch-pairs and distribution-layer switch-pairs, while using trunk ports between access layer and distribution layer switches (if the access layer switches are L2).

Author

Commented:
Any rules that determines when to use Trunk ports and when to use the Routed port betwwen switches and between switch and router?
TimotiStDatacenter Technician
Top Expert 2012
Commented:
There are no hard rules. These are all "tools", that can be used to implement the planned network design. And there is not just one "good" solution: if it works, does what you want it to do, then it's a good solution.

On our main campus, we use trunk ports between our core Catalyst 6500 and Catalyst 3560 access switches. We only do routing in the core, but want the possibility to deploy any vlan on any access switch on campus, so routed ports are not an option in this case.
Our remote installations (dormitory, guesthouse, etc.) are linked to the core with leased fibre cables. All locations have a core L3 switch, and these switches are linked to our core 6500 using routed ports. That way, no broadcast storm, address flood, STP issue or any other L2 problem may propagate to our core switch. On the other hand, I can't provision an access port with my DMZ server vlan (located on the main campus) in the dormitory, for example.

Author

Commented:
1- With L2 to L2 switch conection we use Trunk port to aloow Vlans from each switch to talk to the othe switch. Though I believe we still need a router on a stick make that happen.  Correct ?

2-With L2 to L3 switch I would say it should be the same as point 1, we need a trunk port between L2 and L3 switch and a router on a stick.

3-With L3 to L3 switch, why should we use Trunk port instead of Routed port or the other way around.
Datacenter Technician
Top Expert 2012
Commented:
1 - Correct. L2 switches can't route, so they can't even have routed ports. If you want to route traffic between vlans, you'll need a router-on-a-stick, or an L3 switch.

2 - There might be some rare cases where you want to connect an L2 switch without vlans to a routed port on an L3 switch, but 99% of the time, you don't want that, so you usually use trunk ports.

3 - Still it depends on what do you want to achieve. The Campus Network Design Guide of Cisco has some recommendations on it:
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/HA_campus_DG/hacampusdg.html#wp1108899

Author

Commented:
Thank you Guys!