cisco ccna- how to configure multi-layer switch

CISCO CCNAHOW TO CONFIGURE MULTI-LAYER SWITCHTo watch our Cisco CCNA Training Videos Please Check out the link below:www.asmed.com/c1

ASM Educational Center Inc. (ASM)Where Training, Technology & Service ConvergePhone: (301) 984-7400

HOW TO CONFIGURE MULTI-LAYER SWITCH

Layer 3 Switch Now that we have seen how a “router on a stick” works, we can introduce the Layer 3 switch. In the “router on a stick” topology, what if we could bring the router inside the switch? In essence, what if we could give the switch (a layer 2 device) the capability to route (a Layer 3 function). This is what a Layer 3 switch is capable of doing.

HOW TO CONFIGURE MULTI-LAYER SWITCH There are three points we need to remember:

By default, the routing capability is not turned on in a Layer 3 switch. We need to issue the ip routing command to enable it from global config.

Switch#Switch#conf tEnter configuration commands, one per line. End with CNTL/Z.Switch(config)#ip routingSwitch(config)#

HOW TO CONFIGURE MULTI-LAYER SWITCHOn a Layer 2 switch the ports cannot be assigned an IP address. If a switch is to act like a router, we need a way to assign IP addresses to ports. This is done by the command switchport under the interface. Switchport makes the port behave like a Layer 2 port, whereas no switchport will make it behave like a Layer 3 port; is it a toggle. By default, a Layer 3 switch will have all of the ports in Layer 2 mode. By issuing the no switchport command, we will be able to assign IP addresses to Layer 3 ports.

Switch(config)#Switch(config)#conf tSwitch(config)#interface fa0/5Switch(config-if)#no switchportSwitch(config-if)#%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to down%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/5, changed state to upSwitch(config-if)#ip address 192.168.1.50 255.255.255.0Switch(config-if)#

HOW TO CONFIGURE MULTI-LAYER SWITCHIf the switch needs to route using the virtual router, we need to be able to assign IP addresses to that virtual router. The virtual router inside the switch will be acting as the Default Gateway. This is done by creating virtual interfaces using the command interface vlan X, where X is the VLAN ID. You can shutdown or bring up this interface, just like any other interface.Switch(config)#vlan 10Switch(config-vlan)#name ManagementSwitch(config-vlan)#exitSwitch(config)#int vlan 10Switch(config-if)#%LINK-5-CHANGED: Interface Vlan10, changed state to up%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan10, changed state to upSwitch(config-if)#ip add 11.11.11.11 255.255.255.0Switch(config-if)#endSwitch#%SYS-5-CONFIG_I: Configured from console by console

HOW TO CONFIGURE MULTI-LAYER SWITCH We can check for the routed ports by looking at the routing table on the Layer 3 switch. We use the same command we did on a router, namely sh ip route.

Switch#

Switch#sh ip route

Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area

* – candidate default, U – per-user static route, o – ODR

P – periodic downloaded static route

HOW TO CONFIGURE MULTI-LAYER SWITCH Gateway of last resort is not set

11.0.0.0/24 is subnetted, 1 subnetsC 11.11.11.0 is directly connected, Vlan10C 192.168.1.0/24 is directly connected, FastEthernet0/5Switch#


Let’s see the Layer 3 switch in action.Build the following topology:

HOW TO CONFIGURE MULTI-LAYER SWITCH We start by creating the VLAN’s and assign ports to them, just like a L2 switch.

Switch>

Switch>en

Switch#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)#vlan 2

Switch(config-vlan)#name Sales

Switch(config-vlan)#vlan 3

HOW TO CONFIGURE MULTI-LAYER SWITCH Switch(config-vlan)#name EGR

Switch(config-vlan)#exit

Switch(config)#interface range fa0/1 – 2

Switch(config-if-range)#switchport mode access

Switch(config-if-range)#switchport access vlan 2

Switch(config-if-range)#int range fa0/4 – 5

Switch(config-if-range)#switchport mode access

Switch(config-if-range)#switchport access vlan 3

HOW TO CONFIGURE MULTI-LAYER SWITCH Let’s check the VLAN port assignments, just like a Layer 2 switch:

Switch#sh vlan brVLAN Name Status Ports

1 default active Fa0/3, Fa0/6, Fa0/7, Fa0/8Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16Fa0/17, Fa0/18, Fa0/19, Fa0/20Fa0/21, Fa0/22, Fa0/23, Fa0/24

Gig0/1, Gig0/2

2 Sales active Fa0/1, Fa0/23 EGR active Fa0/4, Fa0/5


Assign IP addresses to our hosts and set the Default Gateway as per the topology. Pings to hosts in the same VLAN will succeed; however, pings to hosts from different VLAN will fail (no inter-vlan communication).

HOW TO CONFIGURE MULTI-LAYER SWITCH Create the virtual interfaces on the Layer 3 switch which will act as the Default Gateway:

Switch#

Switch#conf t


Switch(config)#int vlan 2

Switch(config-if)#

%LINK-5-CHANGED: Interface Vlan2, changed state to up

HOW TO CONFIGURE MULTI-LAYER SWITCH %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan2, changed state to up

Switch(config-if)#ip add 10.10.10.100 255.255.255.0

Switch(config-if)#int vlan 3

Switch(config-if)#

%LINK-5-CHANGED: Interface Vlan3, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan3, changed state to up

HOW TO CONFIGURE MULTI-LAYER SWITCH Switch(config-if)#ip add 20.20.20.100 255.255.255.0

Switch(config-if)#end

Switch#

%SYS-5-CONFIG_I: Configured from console by console

HOW TO CONFIGURE MULTI-LAYER SWITCH Look at the routing table on the Layer 3 switch. We expect to see the virtual interfaces with connected networks:

Switch#sh ip route

Default gateway is not set

Host Gateway Last Use Total Uses Interface

ICMP redirect cache is empty

HOW TO CONFIGURE MULTI-LAYER SWITCH Note the routing table is empty, why? We have not enabled the routing feature on the Layer 3 switch. Let’s enable it now:

Switch#conf t


Switch(config)#ip routing

Switch(config)#end

Switch#


HOW TO CONFIGURE MULTI-LAYER SWITCH Let’s look at the routing table, now that routing has been enabled:

Switch#sh ip route









10.0.0.0/24 is subnetted, 1 subnets

C 10.10.10.0 is directly connected, Vlan2



Switch#

HOW TO CONFIGURE MULTI-LAYER SWITCH A ping to the Default Gatewayand a ping to hosts acrossVLAN’s should now succeed.

Let’s verify:


To test a routed port,

let’s add a router to the topology:

HOW TO CONFIGURE MULTI-LAYER SWITCH On the switch, go to interface fa0/10 and configure the port:

Switch#

Switch#conf t


Switch(config)#int fa0/10

Switch(config-if)#no sw

Switch(config-if)#no switchport

HOW TO CONFIGURE MULTI-LAYER SWITCH Switch(config-if)#ip add

Switch(config-if)#ip address 192.168.1.50 255.255.255.0

Switch(config-if)#end

Switch#


HOW TO CONFIGURE MULTI-LAYER SWITCH On the router, go to interface fa0/0 and configure the port:

Router>en

Router#conf t


Router(config)#int fa0/0

Router(config-if)#ip add 192.168.1.1 255.255.255.0

Router(config-if)#no shut

Router(config-if)#

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

HOW TO CONFIGURE MULTI-LAYER SWITCH %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

Back on the Layer 3 switch, let’s check the routing table:

Switch#

Switch#sh ip route













C 192.168.1.0/24 is directly connected, FastEthernet0/10

Switch#

HOW TO CONFIGURE MULTI-LAYER SWITCH Notice that interface fa0/10 is acting like a routed port and has an IP address. Let’s see if we can ping the router:

Switch#ping 192.168.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:

.!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 0/0/0 ms

Switch#

Perfect. We have connectivity to the router. Now will a ping from the PC’s to the router succeed?

HOW TO CONFIGURE MULTI-LAYER SWITCH The ping test fails, why? Remember that we need to have bi-directional communication. The Layer 3 switch knows about the routers prefix and can route traffic out to the router; however, does the router know about the networks traffic is originating from? Does it know about 10.10.10.0 and 20.20.20.0 network? Let’s find out.

HOW TO CONFIGURE MULTI-LAYER SWITCH Router# Router#sh ip route Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area * – candidate default, U – per-user static route, o – ODR P – periodic downloaded static route



Router#

The router only knows about the connected network, namely the link between the Layer 3 switch and the router. It does not know about networks behind the Layer 3 switch. How can we correct this? We saw a number of options; we can configure a default route, or a static route. Other options include dynamic routing with RIP, EIGRP, or OSPF.

HOW TO CONFIGURE MULTI-LAYER SWITCH Let’s configure a couple of static routes here:

Router#

Router#conf t


Router(config)#ip route 10.10.10.0 255.255.255.0 192.168.1.50

Router(config)#ip route 20.20.20.0 255.255.255.0 192.168.1.50

Router(config)#end

Router#


HOW TO CONFIGURE MULTI-LAYER SWITCH Are the routes in the routing table now?

Router#sh ip route










S 10.10.10.0 [1/0] via 192.168.1.50


S 20.20.20.0 [1/0] via 192.168.1.50


Router#

Can we ping from the PC’s?

HOW TO CONFIGURE MULTI-LAYER SWITCH Yes, we now have connectivity. Remember, if packets are routed to a destination, a route back must exist. Also, the route taken to a destination is not necessarily the route that is taken back.

GOOD LUCK!To watch our Cisco CCNA Training Videos Please Check out the link below:www.asmed.com/c1

ASM Educational Center Inc. (ASM)Where Training, Technology & Service ConvergePhone: (301) 984-7400