Router - switch interconnection

[student100]

Hello: I'd like to know what is the purpose for connecting a router to a switch access port (so far i've only configured router - switch links as trunk)

For example:

Router:

interface FastEthernet0/0

description Link to Switch
ip address 10.1.1.1 255.255.255.0

Switch:

interface FastEthernet0/2
description Link to Router
switchport access vlan 11
switchport mode access

Thanks in advance.

David

[milan.kulik]

Hi,

it depends on your LAN topology.

There might be only one VLAN/subnet used.

Or there is an L3 switch inside the LAN providing inter-VLAN routing.

It that cases you don't need  any trunk configured on your router.

HTH,

Milan

[west33637 · Accepted solution]

hello David. if you want to pass only one VLAN through from the router to the switch, then you make the switch port an access port.

using your example,

switchport access vlan 11

if this is a layer 2 switch that does not do routing, then any other switch port that is not configured for vlan 11 will not have access to the router's interface.

say on the switch you configure 5 other ports to access vlan 11. They will be able to access the router and access each other, because they are all in the same VLAN. say you have another 3 ports on the switch that are in VLAN 1, they will be able to access each other, but wont be able to access the devices on VLAN 11.

Whereas, if you configured trunking between the router and the switch, the router will pass broadcast traffic for both VLAN 1 and VLAN 11.

so in short, you can use the access port configuration to segregate the network or if you have only one vlan to pass between the layer  2 switch and the router.

please rate if this helps!

[student100]

Thank you all for your help.

[Joseph W. Doherty]

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Posting

It's similar to how hubs (or switches w/o VLAN support) and/or routers (pre-Ethernet subinterface/dot1Q support) work.