Which authentication strategy authenticates IS-IS hello PDUs only?

4 thoughts on “Which authentication strategy authenticates IS-IS hello PDUs only?”

1. Correct Answer – A

   The next set of commands adds the required hello authentication to each of r5’s level 2 interfaces. Authentication is not configured on interface lo0 because LSP flooding and adjacency formation do not occur on this virtual interface:

   [edit protocols isis] lab@r5# set interface as1.0 hello-authentication-type md5

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2. agree with Dejan, in jncis old book it’s written:

   Configuring authentication at the IS-IS interface level secures only the Hello PDUs transmitted
   by the local router and is used in two different situations.

   and:

   https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/hello-authentication-type-edit-protocols-isis.html

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   1. From your link you should have seen it is per interface but level based:

      [edit protocols isis interface interface-name level number]

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3. should be A, interface authentication affects only hello PDU, level authentication affects all PDUs. When both configured, interface takes presedence

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