One-arm routing and 30% switch

One-arm routing

One-arm routing refers to the interconnection between different VLANs (Virtual Local Area Networks) that were originally isolated from each other by configuring sub-interfaces on one interface of the router.

• Advantages: Realize communication between different vlans, help to understand and learn vlan principles and sub-interface concepts
• Disadvantages: It is easy to become a single point of failure in the network, the configuration is slightly complicated, and it is of little practical significance

Experimental topology one

Switch Configuration

Configuring routing (one-arm routing)

PC1 ping 192.168.2.1

Layer 3 switch

• Layer 3 switching = Layer 2 switching + Layer 3 forwarding
• Layer 3 switches have some router functions and work at the network layer

The Forwarding Principle of Layer 3 Switches

In this network, the source host, destination of communicationThe hosts are connected to the same Layer 3 switch, but they are in different VLANs (network segments).
For the Layer 3 switch, the two hosts are located in its directly connected network segment, and the routes corresponding to their IPs are all directly connected routes.

Function:
Layer 3 switching technology can realize inter-vlan communication;
speed up data exchange within large local area networks.

Advantages:
Can do one routing, multiple forwarding
one routing: The first packet is processed by the three-layer engine, re-encapsulates the MAC, and then routes and forwards the packet;
multiple exchanges: After the first packet is forwarded, an MSL entry will be created in the hardware. The MSL contains the FIB (forwarding information base: including the adjacent host IP and vlanid),Adjacency table (including MAC addresses of adjacent hosts), Re-encapsulate data frames by querying FIB and adjacency table, and forward data from corresponding ports.

Experimental topology two

Configure Layer 2 switches, create vlans in batches, enter ports e0/0/1, e0/0/2, and e0/0/4, set the ports to access mode, and setPut each vlan into the corresponding vlan; enter the e0/0/3 port, set the port to trunk mode, and allow all vlan communication.

Configure the Layer 3 switch, enter port g0/0/1, set the port to Trunk mode, and allow all vlan communication; set vlan in batches, then enter the logical interface of VLAN10, set the port'sIP address and subnet mask


PC1 communicates with PC2, PC3 (ping 192.168.2.1, ping192.168.3.1)

Command extension:

One-arm routing:

• dotlq termination vid //The single-layer VLAN ID
used to configure the sub-interface dotlq termination
• arp broadcast enble //If not configured, the arp broadcast cannot be actively sent, and the IP packet will be directly discarded and not forwarded

Layer 3 switch;

• interface vlanif //Used to enter the vlanif interface view
• display ip interface brief //View port IP information