CCNP

Layer-3 Switching (Inter VLAN Routing)

mls

When you begin to network lessons, it is known that switching is layer – 2 ! Omg it is something like that 11 is not divided to 4. But after the pre school you learn it that it is divided to 4. So today we are gonna learn that Layer-3 Switching, what is inter vlan routing ! Inter vlan routing is made with two methods : Router on a stick and Multi-Layer switching.

ROUTER ON A STICK

roas

As we talked in VLAN subject, different VLANs can’t communicate each other without a Layer -3 device ! As you can see here , we have a router to establish communication with Vlan 10 and Vlan 20. If VLAN 10 wants to communicate with VLAN 20 , packet goes to router first and routed to VLAN 20 via sub – interfaces. That is a slow operation because of routing is slow.

ROUTER ON A STICK CONFIGURATION

Router(conf)#interface Fa0/0.10 (//10 is mandotary , but it is recommended//)
Router(conf-if)#encapsulation dot1q 10
Router(conf-if)#ip address 10.1.10.1 255.255.255.0

 

MULTI-LAYER SWITCHING

mls

As you can see on the figure above, there is just one multi layer switch and no any other router or something like that ! There are two vlans, vlan 10 and 20 and they can communicate because this is a Layer – 3 switch ! It makes routing on cable-speed and has a great backplane bandwith so that it’s much faster than inter vlan routing via routing on a stick.

MULTI-LAYER SWITCHING CONFIGURATION

SwitchA(conf)#ip routing
SwitchA(conf)#interface vlan 10
SwitchA(conf-if)#ip address 10.1.10.1 255.255.255.0
SwitchA(conf)#interface vlan 20
SwitchA(conf)#ip address 10.1.20.1 255.255.255.0

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