ZyXEL Communications ISG50 User Manual
Chapter 15 Routing Protocols
ISG50 User’s Guide
304
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.
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
• 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.
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.
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.
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.
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.
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.
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.
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.
Table 92
Configuration > Network > Routing Protocol > RIP (continued)
LABEL
DESCRIPTION