Learning diary - (routing and switching technology) layer 3 switch

One 、 Related knowledge

1、 What is layer 3 Switching Technology ？

1. Simply speaking , Layer 2 switching technology + Three layer forwarding technology . It solves the problem of network segment division in LAN , The situation that the subnet must be managed by the router , It also avoids the low speed of traditional routing 、 Network bottlenecks caused by complexity .
2. A device with three-layer switching function is ： A layer 2 switch with layer 3 routing function , But it is an organic combination of the two , It is not simply to superimpose the relevant hardware and software of the router on the layer-2 switch .
3. principle ： Suppose two uses IP The site of the agreement A、B Use IP Protocol to communicate ,A towards B Before sending data , First judge and B Is it the same subnet , If it is , Use layer 2 to forward , If not on the same subnet ,A Want to “ Default gateway ”（ Default gateway IP The address is actually the switching module of the layer 3 switch ） send out ARP（ Address resolution ） Packet
4. advantage ： Because only three layers are used in the routing process , The rest is forwarded through layer 2 , So the speed of layer 3 switch is very fast , It's similar to the second floor , And it's much cheaper than routers .

2、 The difference between layer 3 switch and layer 2 switch

1. The main functions are different ： On the second floor 、 Three layer switches can exchange and forward data frames , But there are also three-layer switches IP Routing functions
2. Different places of use ： The layer-2 switch is used for OSI The second layer of the model , Layer 3 switches are used in OSI The third layer of the model .
3. The way data is processed is different ： The layer 2 switch uses Layer 2 switching forwards data frames , Three layer switching routing module Use layer 3 switching IP Data packets .

3、 The difference between layer 3 switch and router

1、 Now the layer 3 switch can perform most of the functions of the traditional router

2、 The three-layer switch has the following characteristics ：

1. Forward the business flow based on the third layer
2. Full exchange function
3. Can complete special services , Such as message filtering or authentication
4. Execute or not execute the routing function

3、 Switches are generally used for LAN-WAN The connection of , Switch belongs to bridge , Acting on the data link layer ： Routers are generally used for WAN-WAN The connection of , It works on the network layer

4、 Routers are more powerful than switches , But the price is high , Relatively slow , The layer-3 switch has the ability to forward messages at line speed , It also has a good control function of the router .

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Two 、 A simple example （ Three layer switch 、VLAN Routing between ）

Three layer switch

1、 Simple topology

2、 Related codes

  Three layer switch 1：

Switch>en

Switch#conf t

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

Switch(config)#host R1

R1(config)#int

R1(config)#interface F

R1(config)#interface FastEthernet 0/1

R1(config-if)#no sw

R1(config-if)#no switchport （ After entering the interface , Change the layer-2 interface into the layer-3 interface ）

R1(config-if)#                The following two lines are tips

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up

R1(config-if)#ip add

R1(config-if)#ip address 192.168.12.1 255.255.255.0

R1(config-if)#no sh

R1(config-if)#no shutdown

R1(config-if)#

R1(config-if)#e

R1(config-if)#exit

R1(config)#interface FastEthernet 0/2

R1(config-if)#no sw

R1(config-if)#no switchport

R1(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up

R1(config-if)#ip add

R1(config-if)#ip address 192.168.1.254 255.255.255.0

R1(config-if)#no sh

R1(config-if)#no shutdown

R1(config-if)#e

R1(config-if)#exit

R1(config)#interface FastEthernet 0/3

R1(config-if)#no switchport

R1(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/3, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/3, changed state to up

R1(config-if)#ip address 192.168.2.254 255.255.255.0

R1(config-if)#no shutdown

R1(config-if)#e

R1(config-if)#exit

R1(config)#end

R1#

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

R1#show ip route    In this section, the route is not opened after configuration , need ip routing Turn on the routing function

Default gateway is not set

Host Gateway Last Use Total Uses Interface

ICMP redirect cache is empty

R1#conf t

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

R1(config)#ip routing （ Turn on the routing function ）

R1(config)#end

R1#

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

R1(config)#ip route 192.168.3.0 255.255.255.0 192.168.12.2  （ Configure static routing ）

R1(config)#end

R1#

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

R1#show 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

Gateway of last resort is not set

C 192.168.1.0/24 is directly connected, FastEthernet0/2

C 192.168.2.0/24 is directly connected, FastEthernet0/3

S 192.168.3.0/24 [1/0] via 192.168.12.2

C 192.168.12.0/24 is directly connected, FastEthernet0/1

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Three layer switch 2：

Switch>en

Switch#conf t

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

Switch(config)#host

Switch(config)#hostname S2

S2(config)#int Fq

S2(config)#int F

S2(config)#int FastEthernet 0/1

S2(config-if)#no sw

S2(config-if)#no switchport

S2(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up

S2(config-if)#ip add

S2(config-if)#ip address 192.168.12.2 255.255.255.0

S2(config-if)#no sh

S2(config-if)#no shutdown

S2(config-if)#e

S2(config-if)#exit

S2(config)#int FastEthernet 0/2

S2(config-if)#no switchport

S2(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up

S2(config-if)#ip address 192.168.3.254 255.255.255.0

S2(config-if)#no shutdown

S2(config-if)#end

S2#

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

S2#conf t

S2(config)#ip routing

S2(config)#end

S2#

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

S2#show 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

Gateway of last resort is not set

C 192.168.3.0/24 is directly connected, FastEthernet0/2

C 192.168.12.0/24 is directly connected, FastEthernet0/1

S2#conf t

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

S2(config)#ip route 192.168.1.0 255.255.255.0 192.168.12.1  Configure static routing  

S2(config)#ip route 192.168.2.0 255.255.255.0 192.168.12.1  

S2(config)#end

S2#show ip route

Configure the routing table after static routing

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

Gateway of last resort is not set

S 192.168.1.0/24 [1/0] via 192.168.12.1

S 192.168.2.0/24 [1/0] via 192.168.12.1

C 192.168.3.0/24 is directly connected, FastEthernet0/2

C 192.168.12.0/24 is directly connected, FastEthernet0/1

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result ： The result is that the layer 3 switch enables the routing function , All network segments can be interconnected . （ notes , After completing the configuration of the layer-3 switch, configure the static route ）

Here are just ping PC3（192.168.2.1） and PC5（192.168.3.1）, The layer 3 switch is finished .

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  Second example ：VLAN Routing between

If you want to achieve VLAN Routing between , It needs to be divided into two steps

1. First step ,VLAN Inter Division , Realize the functions of the second layer
2. The second step ,VLAN Routing between

1、 Simple topology

 2、 Related codes

S1( Three layer switch )：

Switch>en

Switch#conf t

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

Switch(config)#host

Switch(config)#hostname S1

This part is VLAN Division Arrange according to the topology , Divide into vlan10、20、30 

S1(config)#vlan 10 

S1(config-vlan)#exit

S1(config)#vlan 20

S1(config-vlan)#exit

S1(config)#vlan 30

S1(config-vlan)#exit

This part divides the corresponding interfaces into corresponding VLAN 

S1(config)#int f   

S1(config)#int fastEthernet 0/1

S1(config-if)#sw

S1(config-if)#switchport md

S1(config-if)#switchport mod

S1(config-if)#switchport mode ac

S1(config-if)#switchport mode access

S1(config-if)#sw

S1(config-if)#switchport ac

S1(config-if)#switchport access ?

vlan Set VLAN when interface is in access mode

S1(config-if)#switchport access vlan 10

S1(config-if)#e

S1(config-if)#exit

S1(config)#int fastEthernet 0/2

S1(config-if)#switchport mode access

S1(config-if)#switchport access vlan 20  These three commands are the key

S1(config-if)#e

S1(config-if)#exit

S1(config)#int fastEthernet 0/3

S1(config-if)#switchport mode access

S1(config-if)#switchport access vlan 30

S1(config-if)#e

S1(config-if)#exit

S1(config)#%SPANTREE-2-RECV_PVID_ERR: Received 802.1Q BPDU on non trunk FastEthernet0/4 VLAN1.

%SPANTREE-2-BLOCK_PVID_LOCAL: Blocking FastEthernet0/4 on VLAN0001. Inconsistent port type.

S1(config)#

This is the configuration trunk mouth Be careful , The layer 3 switch cannot be configured trunk mouth , Must be configured on the layer-2 switch , Then the interface of the same link automatically becomes trunk Pattern .

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to up

The second step ：vlan Routing between You only need to configure on the layer 3 switch , The second floor does not need .

S1(config)#interface v

S1(config)#interface vlan 10

S1(config-if)#

Prompt information （ The following two are also ）

%LINK-5-CHANGED: Interface Vlan10, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan10, changed state to up

S1(config-if)#ip add

S1(config-if)#ip address 192.168.10.254 255.255.255.0 （ configure gateway ）

S1(config-if)#no sh

S1(config-if)#no shutdown （ Can ignore not write ）

S1(config-if)#e

S1(config-if)#exit

S1(config)#interface vlan 20

S1(config-if)#

%LINK-5-CHANGED: Interface Vlan20, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan20, changed state to up

S1(config-if)#ip address 192.168.20.254 255.255.255.0（ configure gateway ）

S1(config-if)#no shutdown

S1(config-if)#

S1(config-if)#e

S1(config-if)#exit

S1(config)#interface vlan 30

S1(config-if)#

%LINK-5-CHANGED: Interface Vlan30, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan30, changed state to up

S1(config-if)#ip address 192.168.30.254 255.255.255.0（ configure gateway ）

S1(config-if)#no shutdown

S1(config-if)#e

S1(config-if)#exit

S1(config)#ip routing （ Open routing ）

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S2（ Two-layer switch ）:

Switch>en

Switch#conf t

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

Switch(config)#host S2

Switch(config)#host S2

This part is VLAN Division Arrange according to the topology , Divide into vlan10、20、30 

S2(config)#vlan 10

S2(config-vlan)#e

S2(config-vlan)#exit

S2(config)#vlan 20

S2(config-vlan)#e

S2(config-vlan)#exit

S2(config)#vlan 30

S2(config-vlan)#e

S2(config-vlan)#exit

This part divides the corresponding interfaces into corresponding VLAN 

S2(config)#int f

S2(config)#int fastEthernet 0/1

S2(config-if)#sw

S2(config-if)#switchport mode

S2(config-if)#switchport mode ac

S2(config-if)#switchport mode access

S2(config-if)#sw

S2(config-if)#switchport ac

S2(config-if)#switchport access vlan 10

S2(config-if)#e

S2(config-if)#exit

S2(config)#int fastEthernet 0/2

S2(config-if)#switchport mode access

S2(config-if)#switchport access vlan 20

S2(config-if)#e

S2(config-if)#exit

S2(config)#int fastEthernet 0/3

S2(config-if)#switchport mode access

S2(config-if)#switchport access vlan 30

S2(config-if)#end

S2#

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

VLAN surface

S2#show vlan brief

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/4, Fa0/5, Fa0/6, Fa0/7

Fa0/8, Fa0/9, Fa0/10, Fa0/11

Fa0/12, Fa0/13, Fa0/14, Fa0/15

Fa0/16, Fa0/17, Fa0/18, Fa0/19

Fa0/20, Fa0/21, Fa0/22, Fa0/23

Fa0/24, Gig0/1, Gig0/2

10 VLAN0010 active Fa0/1

20 VLAN0020 active Fa0/2

30 VLAN0030 active Fa0/3

1002 fddi-default active

1003 token-ring-default active

1004 fddinet-default active

1005 trnet-default active

S2#conf t

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

To configure trunk mouth

S2(config)#int f

S2(config)#int fastEthernet 0/4

S2(config-if)#sw

S2(config-if)#switchport mod

S2(config-if)#switchport mode tr

S2(config-if)#switchport mode trunk

S2(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to up

S2(config-if)#end

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result ：

The result of the first step ： identical VLAN Hosts of can interact ping through

The second step is to complete the result ： Different VLAN The host between can communicate through the three-layer switch

ping PC2(192.168.20.1)

tracert It depends on where its bag goes

Pictured , After 192.168.10.254 That is, the route through the layer 3 switch .

 

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  This article is written here , Please point out any mistakes . thank ！！！