1. Authentication
   1. only offers MD5
   2. authenticates source of routing update packets
   3. prevents false routing updates
   4. ignores malicious routing updates
   5. Configure:
      1. " #Key Chain 'name' "
         1. " #Key 'number' "
            1. " #Key-String 'text' "
      2. "#interface 'interface #' "
         1. " #ip authentication mode eigrp 'AS #' md5 "
         2. " #ip authentication Key Chain eigrp 'AS #' 'key chain name' "
   6. Configure Key Chain
      1. Key Chain ID
         1. KC ID must match on both routers
         2. Specify password
         3. Optional: Accept & Expire Lifetime configuration
2. EIGRP Stubs
   1. Types:
      1. Receive Only
         1. Does not advertise networks
      2. Connected
         1. Advertises directly connected networks
      3. Static
         1. Advertises static routes (redistributed)
      4. Summary
         1. Advertises summary routes
      5. Redistribute
         1. Advertises redistributed routes
   2. Default is : Connected + Summary
   3. Commands:
      1. " #router eigrp 'AS #'
         1. " #eigrp stub 'stub type' "
3. Named EIGRP
   1. Configured globally
      1. IOS 15.x
   2. Commands:
      1. " #router eigrp 'name' "
         1. " #address family 'ipv4 or 6' AS 'AS #' "
            1. " #network 'ip address' "
            2. " #af-interface 'interface #' "
            3. " #authentication mode md5 "
            4. " #authentication key-chain 'key chain name' "