Netgear GSM7212P GSM5212P/GSM7212P/GSM7212F/GSM7224P Administration Manual - Page 39

4. Port Routing 4 This chapter provides the following sections: • Port Routing Configuration on page 40 • Enable Routing for the Switch on page 41 • Enable Routing for Ports on the Switch on page 41 • Add a Default Route on page 44 • Add a Static Route on page 45 The first networks were small enough for the end stations to communicate directly. As networks grew, Layer 2 bridging was used to segregate traffic, a technology that worked well for unicast traffic, but had problems coping with large quantities of multicast packets. The next major development was routing, where packets were examined and redirected at Layer 3. End stations needed to know how to reach their nearest router, and the routers had to interpret the network topology so that they could forward traffic. Although bridges tended to be faster than routers, using routers allowed the network to be partitioned into logical subnetworks, which restricted multicast traffic and also facilitated the development of security mechanisms. An end station specifies the destination station's Layer 3 address in the packet's IP header, but sends the packet to the MAC address of a router. When the Layer 3 router receives the packet, it will minimally: • Look up the Layer 3 address in its address table to determine the outbound port. • Update the Layer 3 header. • Re-create the Layer 2 header. The router's IP address is often statically configured in the end station, although the 7000 Series Managed Switch supports protocols such as DHCP that allow the address to be assigned dynamically. Likewise, you can assign some of the entries in the routing tables used by the router statically, but protocols such as RIP and OSPF allow the tables to be created and updated dynamically as the network configuration changes. Chapter 4. Port Routing | 39