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Authentication with different Routing Protocols

 Routing Protocol Authentication

Authentication is crucial in routing protocols to ensure the integrity and authenticity of routing updates. Most protocols support different types of authentication mechanisms like plain text, MD5, and more advanced cryptographic methods such as HMAC-SHA-256.

EIGRP Authentication

  • EIGRP Authentication: EIGRP supports both MD5 (in classic mode) and HMAC-SHA-256 (in named mode). Authentication ensures that packets exchanged between EIGRP neighbors are verified using pre-shared keys.
    • Technical Tip: Use HMAC-SHA-256 in named mode as it is stronger than MD5.

Example configuration for MD5 in classic mode:

key chain EIGRP-R2-R4

 key 1

  key-string CCIE

!

interface eth0/2

 ip authentication mode eigrp 1 md5

 ip authentication key-chain eigrp 1 EIGRP-R2-R4

Example for HMAC-SHA-256 in named mode:

router eigrp ONE

 address-family ipv4 unicast autonomous-system 1

  af-interface Ethernet0/2

   authentication mode hmac-sha-256 CCIE

  • Technical Tip: For passwords containing special characters, escape sequences might be necessary. For example, entering "C?IE" requires pressing Esc and q before entering the ? character.

OSPF Authentication

OSPF supports three types of authentication:

  • Type 0: No authentication.
  • Type 1: Plain text authentication.
  • Type 2: MD5-based authentication.
  • Cryptographic Authentication: Newer OSPF implementations support SHA-based authentication, such as HMAC-SHA-256.

OSPF MD5 authentication example:

interface GigabitEthernet0/1

 ip ospf authentication message-digest

 ip ospf message-digest-key 1 md5 OSPF-KEY

Cryptographic authentication example (SHA-256):

key chain OSPF

 key 1

  key-string CCIE

  cryptographic-algorithm hmac-sha-256

interface GigabitEthernet0/1

 ip ospf authentication key-chain OSPF

  • Key Rollover: In MD5-based OSPF, multiple keys can be configured, and routers go through a key rollover process where the last key added is used to sign packets, while received packets are authenticated with the key ID in the packet.
  • Virtual Links: If OSPF authentication is enabled in Area 0, it must also be enabled on virtual links since they are considered part of Area 0. Virtual links use demand circuits, suppressing hello messages to avoid keeping the link up unless there is a topology change.
  • Technical Tip: Be cautious with key numbering in OSPF. The newest key is not determined by the numeric value but by the order in which it was added.

 

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