ZyXEL Communications 200 Series User Manual

 Chapter 13 Routing Protocols

ZyWALL USG 100/200 Series User’s Guide

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.

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 94   Network > Routing Protocol > RIP (continued)