Single arm Routing - logical interface (detailed transmission process!)

Single arm routing

Single arm routing (router-on-a-stick) refers to the interconnection and interworking between different VLAN s (virtual LANs) isolated from each other by configuring a sub interface (or "logical interface", there is no real physical interface) on one interface of the router.

Advantages and disadvantages

Advantages: realize the communication between different VLANs, help to understand and learn VLAN principle and sub interface concept.
Disadvantages: it is easy to become a single point of network failure, with slightly complex configuration and little practical significance.

Experimental topology

Experimental environment

vlan10: pc1(192.168.10.10/24)
vlan20: pc2(192.168.20.20/24)

Experimental purpose

Communication between different VLANs

1. Configure sw layer 2 switch

sw#conf t     ##Enter global mode
Enter configuration commands, one per line.  End with CNTL/Z.
sw(config)#no ip routing   ##Turn off routing
sw(config)#vlan 10,20     ##Creating vlan10 20
sw(config-vlan)#ex
sw(config)#int f1/1          ##Access interface
sw(config-if)#sw mod acc    ##Create access link
sw(config-if)#sw acc vlan 10  ##Put the interface in vlan
sw(config-if)#int f1/2
sw(config-if)#sw mo acc
sw(config-if)#sw acc vlan 20
sw(config-if)#do show vlan-sw b  ##View vlan information

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa1/0, Fa1/3, Fa1/4, Fa1/5
                                                        Fa1/6, Fa1/7, Fa1/8, Fa1/9
                                                        Fa1/10, Fa1/11, Fa1/12, Fa1/13
                                                        Fa1/14, Fa1/15
10   VLAN0010                         active    Fa1/1      ##Put the interface in the corresponding vlan
20   VLAN0020                         active    Fa1/2
1002 fddi-default                     act/unsup 
1003 token-ring-default               act/unsup 
1004 fddinet-default                  act/unsup 
1005 trnet-default                    act/unsup 

sw(config-if)#int f1/0       ##Enter into f1/0 interface
sw(config-if)#sw mo tr    ##Set to trunk link
sw(config-if)#sw tr en dot     
sw(config-if)#do show int f1/0 switchport  ##View interface information

2. Configure R1 router

R1#conf t    ##Global schema
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#int f0/0.1   ##Enter logical sub interface
R1(config-subif)#encapsulation dot1Q 10    ##Encapsulation protocol vlan10
R1(config-subif)#ip add 192.168.10.1 255.255.255.0   ##Setting up gateway
R1(config-subif)#no shut   ##open
R1(config-subif)#ex
R1(config)#int f0/0.2    
R1(config-subif)#encapsulation dot1Q 20    ##Encapsulation protocol VLAN 20
R1(config-subif)#ip add 192.168.20.1 255.255.255.0
R1(config-subif)#no shut
R1(config-subif)#ex
R1(config)#int f0/0     ##Enter physical interface
R1(config-if)#no shut ##open
R1(config-if)#end
R1#show ip int b   ##View interface information

Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  up                    up      
FastEthernet0/0.1          192.168.10.1    YES manual up                    up      
FastEthernet0/0.2          192.168.20.1    YES manual up                    up      
FastEthernet0/1            unassigned      YES unset  administratively down down 

R1#sho ip route    ##View routing table

C    192.168.10.0/24 is directly connected, FastEthernet0/0.1
C    192.168.20.0/24 is directly connected, FastEthernet0/0.2

3. Test different vlan intermediate communication with testing machine

PC1> ip 192.168.10.10 192.168.10.1    ##Set the address and gateway of pc1
PC2> ip 192.168.20.20 192.168.20.1    ##Setting the address and gateway of pc2
PC1> ping 192.168.20.20   ##Test communication

Check the information transmitted with packet capturing




Thank you for reading!

Tags: Linux network

Posted on Tue, 05 Nov 2019 15:57:26 -0500 by azul85