EIGRP

The enhanced version of IGRP proprietary to Cisco. It was first released with v9.21. EIGRP is a classless, distance vector protocol that acts like a link state protocol. VLSM may be used for subnetting and address aggregation. EIGRP uses the same composite metric formula as IGRP but scales it by 256.

facts for your delight and amusement:

• EIGRP routes in IP, IPX, and AppleTalk networks.
• Packets can be authenticated with MD5.
• It uses the multicast address of 223.0.0.10.
• The default Hello interval is 5 seconds, but could be up to 60 on interfaces with T1 speeds or lower.
• The default hold time is three times the Hello interval.

EIGRP packet types:

• Hellos
  
  
• Acknowledgments
  
  
• Updates
  
  
• Queries
  
  
• Replies