3Com 8807 Configuration Manual page 325

Configuring OSPF Configuring the OSPF Area to Support Packet Authentication
Authentication
All the routers in one area must use the same authentication mode (no
authentication, simple text authentication or MD5 cipher text authentication). If
the mode of supporting authentication is configured, all routers on the same
segment must use the same authentication key. To configure a simple text
authentication key, use the authentication-mode simple command. Use the
authentication-mode md5 command to configure the MD5 cipher text
authentication key if the area is configured to support MD5 cipher text
authentication mode.
Perform the following configuration in OSPF area view.
Table 296 Configure the OSPF area to support packet authentication
By default, the area does not support packet authentication.
Configuring OSPF packet authentication
OSPF supports simple authentication or MD5 authentication between neighboring
routers.
Perform the following configuration in interface view.
Table 297 Configure OSPF packet authentication
By default, the interface is not configured with either simple authentication or
MD5 authentication.
Configuring OSPF According to RFC2328, after the area partition of OSPF, not all the areas are equal.
Virtual Link In which, an area is different from all the other areas. Its Area-id is 0.0.0.0 and it is
usually called the backbone Area. The OSPF routes between non-backbone areas
are updated with the help of the backbone area. OSPF stipulates that all the
non-backbone areas should maintain the connectivity with the backbone area.
That is, at least one interface on the ABR should fall into the area 0.0.0.0. If an
area does not have a direct physical link with the backbone area 0.0.0.0, a virtual
link must be created.
If the physical connectivity cannot be ensured due to the network topology
restriction, a virtual link can satisfy this requirement. The virtual link refers to a
logic channel set up through the area of a non-backbone internal route between
Operation
Configure the area to support authentication
type
Cancel the configured authentication mode
Operation
Specify a password for OSPF simple text
authentication on the interface
Cancel simple authentication on the interface undo ospf authentication-mode simple
Specify the interface to use MD5
authentication
Disable the interface to use MD5
authentication
Configuring OSPF
Command
authentication-mode { simple | md5 }
undo authentication-mode
Command
ospf authentication-mode simple
password
ospf authentication-mode md5 key-id key
undo ospf authentication-mode md5
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