ZyXEL Communications ISG50-ISDN User Manual page 312

Chapter 15 Routing Protocols
Authentication Types
Authentication is used to guarantee the integrity, but not the confidentiality, of routing updates. The
transmitting router uses its key to encrypt the original message into a smaller message, and the
smaller message is transmitted with the original message. The receiving router uses its key to
encrypt the received message and then verifies that it matches the smaller message sent with it. If
the received message is verified, then the receiving router accepts the updated routing information.
The transmitting and receiving routers must have the same key.
The ISG50 supports three types of authentication for RIP and OSPF routing protocols:
• None - no authentication is used.
• Text – authentication using a plain text password, and the (unencrypted) password is sent over
the network. This method is usually used temporarily to prevent network problems.
• MD5 – authentication using an MD5 password and authentication ID.
MD5 is an authentication method that produces a 128-bit checksum, called a message-digest, for
each packet. It also includes an authentication ID, which can be set to any value between 1 and
255. The ISG50 only accepts packets if these conditions are satisfied.
• The packet's authentication ID is the same as the authentication ID of the interface that received
it.
• The packet's message-digest is the same as the one the ISG50 calculates using the MD5
password.
For RIP, authentication is not available in RIP version 1. In RIP version 2, you can only select one
authentication type for all interfaces. For OSPF, the ISG50 supports a default authentication type by
area. If you want to use this default in an interface or virtual link, you set the associated
Authentication Type field to Same as Area. As a result, you only have to update the
authentication information for the area to update the authentication type used by these interfaces
and virtual links. Alternatively, you can override the default in any interface or virtual link by
selecting a specific authentication method. Please see the respective interface sections for more
information.
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ISG50 User's Guide