ZyXEL Communications ZyWall USG 50-H Series, User Manual

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Chapter 11 Routing Protocols
ZyWALL USG 50-H User’s Guide
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11.3 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.
• The backbone is the transit area that routes packets between other areas. All other areas
are connected to the backbone.
MD5
Authentication
ID This field is available if the Authentication is MD5 . Type the ID for MD5
authentication. The ID can be between 1 and 255.
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 Select this check box to advertise routes that were learned from the indicated
Name .
Name This field displays other sources of routing information that the ZyWALL can
advertise in the RIP network.
Metric Type the cost for routes provided by the indicated source. 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 ZyWALL.
Reset Click this button to return the screen to its last-saved settings.
Table 87 Network > Routing Protocol > RIP (continued)
LABEL DESCRIPTION