Configuring Authentication; Authentication Requirements - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

JUNOSe 11.0.x IP, IPv6, and IGP Configuration Guide
The highest individual cost is 3. ABR 2 subsequently calculates a cost of 3 for the
aggregate 10.1.1.0 to be announced into area 0.
When Router 3 sends traffic to Router 4, it routes the traffic via ABR 2 because ABR 2
advertises a lower cost than does ABR 1. However, this path is not optimal, because
the traffic must traverse Router 3-->Router 7-->ABR 2--> Router 5-->Router 4. The
path through ABR 1, Router 3-->ABR 1-->Router 4 is a better path, even though
ABR 1 advertised a higher aggregate cost.
You can avoid this kind of suboptimal routing by manually configuring a cost for the
aggregate. The summary LSA then announces the configured cost instead of the
automatically calculated cost. Use the cost keyword with the area range command
to specify a cost for a range of OSPF networks aggregated at an area boundary.

Configuring Authentication

The router supports the following authentication capabilities:
The MD5 algorithm takes as input a message of arbitrary length and produces a
128-bit fingerprint or message digest of the input. MD5 is used to create digital
signatures. It is a one-way hash function, meaning that it takes a message and converts
it into a fixed string of digits, called a message digest.
When using a one-way hash function, you can compare a calculated message digest
with the message digest that is decrypted by using a public key (password). The key
verifies that the message has not been tampered with. This comparison process is
called a hashcheck.
NOTE: You must first issue the address area command before issuing any other
address command.

Authentication Requirements

If you configure either simple password or MD5 authentication, the password or
authentication key must be the same on both sides of an adjacency. When you
change the password or key on one side of an established adjacency, you must also
change it on the other side within the dead interval. Doing this enables a hello packet
that has the latest authentication information to be sent before the dead interval
expires. If the packet is not sent within the dead interval, the adjacency breaks down
and is not reestablished until both sides of the adjacency have the same password
or key.
address authentication-key
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Configuring Authentication
ABR 2-->Router 5-->Router 4
Null authentication
Simple password authentication
MD5 authentication