The basics of Cisco routers are also important. This article introduces the features and architecture of Cisco routers based on Cisco routers' network.
Exchange and routing are terms we often encounter in network interconnection. The exchange mentioned here is completely different from the frame-level exchange in the LAN:
The exchange process refers to how the router transmits messages between two different interfaces. For example, a Cisco router receives a message on Ethernet interface 0.
The router first obtains the MAC header information from the packet and then checks the network layer header.
The router checks whether the routing table has an entry that matches the destination address of the packet.
Assuming that the routing table contains matching entries and the next hop address is another router, the router can arrive through Ethernet interface 1. The router then needs to check the second layer address of the next hop.
If it does not have the address, you need to send an ARP broadcast packet on Ethernet interface 1.
If no ARP response is received, the router discards the packet. If there is a response message, the router establishes an Ethernet frame to the next hop router. In this example, the entire process from the receipt of an Ethernet frame to the establishment and transmission of an Ethernet frame by a router is called an exchange process.
Note: The ARP parsing process is generally not considered part of the exchange process. In the above process, performing a routing table query to find the address of the next hop indicates that the switching process is employed. This is the simplest method of message exchange, so its overhead and delay are relatively large.
All routing protocols ultimately rely on the establishment of a routing table. The router updates the corresponding routing table by receiving routing update messages sent by neighboring routers running the same protocol. We call this the routing process, which is mainly done by the routing processor.
Currently widely used in domestic Cisco routers include 2500 series, 4000 series, 7000 series, and 7500 series. The routing process of these routers is basically similar, but the switching process varies according to its system structure.
The 7000 Series supports process switching, fast switching, autonomous switching, and silicon switching. The Cisco 7500 Series Router has many architectural improvements over the 7000 Series. The functions of the route processor and the switch processor are integrated into the router switch processor. This new architecture reduces the load on the system bus during fast switching.
The integrated functionality optimizes performance, stability, scalability, and security for both the route processor and the switch processor. The 7500 series routers do not support autonomous switching but also silicon switching, which supports more flexible and optimized switching.
The hardware structure of the Cisco 4000/2500 series router is simpler than that of the 7000/7500 series router. These devices only share memory during the exchange process. All message buffers and Caches are located in shared memory, so only fast switching or process switching is supported.
The exchange process needs to make routing by querying the routing table, and other switching technologies use the cache to increase the speed of the exchange because the location of the cache is different and is called different technologies.
The features and architecture of the Cisco router are introduced here. If you have any other questions or needs, please consult our online customer service.