Authentication:
3 Types:
Interface Authentication =====> configured only on interface.
Area Authentication =======> When area authentication is configured, the password is carried in the L1 LSPs, CSNPs and PSNPS. All of the routers are in the same IS-IS area, ex: 49.1234.
Domain Authentication =====> All of the routers are in the same IS-IS Domain (ex: 49.) and are configured with the domain password.
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| Authentication Type | XE/IOS | XRv |
| Interface | interface Ethernet0/0 isis authentication mode md5 isis authentication key-chain isis_int_md5 ! key chain isis_int_md5 key 1 key-string 12345678910 ! OR interface Ethernet0/0 isis password 12345678910 ! |
router isis 20 interface GigabitEthernet0/0/0/0 hello-password hmac-md5 12345678910 ! |
| Area | area-password 12345678910 | router isis 20 lsp-password hmac-md5 12345678910 |
| Domain | domain-password 12345678910 | Option not available |