The characteristics of EIGRP for IPv4 are as follows:
- EIGRP for IPv4 is a hybrid routing protocol (a distance-vector protocol that has link-state protocol characteristics).
- EIGRP for IPv4 uses IP protocol number 88.
- EIGRP for IPv4 is a classless protocol; it supports VLSM.
- The default composite metric uses bandwidth and delay.
- You can factor load and reliability into the metric.
- EIGRP for IPv4 sends partial route updates only when there are changes.
- EIGRP for IPv4 supports MD5 authentication.
- EIGRP for IPv4 uses DUAL for loop prevention.
- EIGRP for IPv4 provides fast convergence.
- By default, EIGRP for IPv4 uses equal-cost load balancing with equal metrics. Unequal-cost load sharing is possible with the variance command.
- The administrative distances are 90 for EIGRP internal routes, 170 for EIGRP external routes, and 5 for EIGRP summary routes.
- EIGRP for IPv4 allows for good scalability and is used in large networks.
- EIGRP for IPv4 multicasts updates to 224.0.0.10.
- EIGRP for IPv4 does not require a hierarchical physical topology.
EIGRP for IPv6 (EIGRPv6) Networks
EIGRP was originally an IPv4 routing protocol, although Cisco has developed IPv6 support into EIGRP to route IPv6 prefixes. EIGRP for IPv6 is configured and managed separately from EIGRP for IPv4; no network statements are used. EIGRP for IPv6 retains all the same characteristics (network discovery, DUAL, modules) and functions as EIGRP for IPv4. The major themes with EIGRP for IPv6 are as follows:
- EIGRP for IPv6 implements protocol-independent modules.
- EIGRP for IPv6 allows for neighbor discovery and recovery.
- EIGRP for IPv6 provides reliable transport.
- It implements the DUAL algorithm for a loop-free topology.
- EIGRP for IPv6 uses the same metrics as EIGRP for IPv4 networks.
- EIGRP for IPv6 uses the same timers as EIGRP for IPv4.
- EIGRP for IPv6 uses the same concepts of feasible successors and feasible distance as EIGRP for IPv4.
- EIGRP for IPv6 uses the same packet types as EIGRP for IPv4.
- EIGRP for IPv6 is managed and configured separately from EIGRP for IPv4.
- EIGRP for IPv6 requires a router ID before it can start running.
- EIGRP for IPv6 is configured on interfaces. No network statements are used.
One difference between EIGRP for IPv4 and EIGRP for IPv6 is the use of IPv6 prefixes and the use of IPv6 multicast group FF02::A for EIGRP updates, which are sourced from the link-local IPv6 address. This means that neighbors do not need to share the same global prefix, except for those neighbors that are explicitly specified for unicast updates.
Another difference is that EIGRP for IPv6 defaults to a shutdown state for the routing protocols and must be manually or explicitly enabled on an interface to become operational. Because EIGRP for IPv6 uses the same characteristics and functions as EIGRP for IPv4, as covered in the previous section, they are not repeated here.