ZyXEL ISG50-PSTN User Guide - Page 304
The OSPF Screen
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Chapter 15 Routing Protocols Table 92 Configuration > Network > Routing Protocol > RIP (continued) LABEL DESCRIPTION MD5 Authentication Key This field is available if the Authentication is MD5. Type the password for MD5 authentication. The password can consist of alphanumeric characters and the underscore, and it can be up to 16 characters long. Redistribute Active OSPF Select this to use RIP to advertise routes that were learned through OSPF. Metric Type the cost for routes provided by OSPF. The metric represents the "cost" of transmission for routing purposes. RIP routing uses hop count as the measurement of cost, with 1 usually used for directly connected networks. The number does not have to be precise, but it must be between 0 and 16. In practice, 2 or 3 is usually used. Active Static Route Select this to use RIP to advertise routes that were learned through the static route configuration. Metric Type the cost for routes provided by the static route configuration. The metric represents the "cost" of transmission for routing purposes. RIP routing uses hop count as the measurement of cost, with 1 usually used for directly connected networks. The number does not have to be precise, but it must be between 0 and 16. In practice, 2 or 3 is usually used. Apply Click this button to save your changes to the ISG50. Reset Click this button to return the screen to its last-saved settings. 15.3 The OSPF Screen OSPF (Open Shortest Path First, RFC 2328) is a link-state protocol designed to distribute routing information within a group of networks, called an Autonomous System (AS). OSPF offers some advantages over vector-space routing protocols like RIP. • OSPF supports variable-length subnet masks, which can be set up to use available IP addresses more efficiently. • OSPF filters and summarizes routing information, which reduces the size of routing tables throughout the network. • OSPF responds to changes in the network, such as the loss of a router, more quickly. • OSPF considers several factors, including bandwidth, hop count, throughput, round trip time, and reliability, when it calculates the shortest path. • OSPF converges more quickly than RIP. Naturally, OSPF is also more complicated than RIP, so OSPF is usually more suitable for large networks. OSPF uses IP protocol 89. OSPF Areas An OSPF Autonomous System (AS) is divided into one or more areas. Each area represents a group of adjacent networks and is identified by a 32-bit ID. In OSPF, this number may be expressed as an integer or as an IP address. There are several types of areas. 304 ISG50 User's Guide