Back to EIGRP GuideENARSI v1.1 scope

EIGRP Address Families: IPv4, IPv6, Global and VRF

Build a clear mental model for named EIGRP address families, then configure and verify isolated IPv4 and IPv6 routing domains without mixing their tables.

Named ModeIPv4IPv6Global TableVRF

Address Families at a Glance

An address family is a routing context inside named EIGRP. It identifies the protocol version and the routing table where EIGRP operates.

IPv4 globalDefault IPv4 table

IPv6 globalDefault IPv6 table

IPv4 VRFIsolated customer table

Core ruleVerify in the right table

Simple meaning: The same physical router can run several independent EIGRP routing contexts. A route in one context does not automatically appear in another.

1. Understand the Routing-Table Model

Context	Address family	Typical verification
Global IPv4	`ipv4 unicast`	`show ip route`
Global IPv6	`ipv6 unicast`	`show ipv6 route`
VRF BLUE IPv4	`ipv4 unicast vrf BLUE`	`show ip route vrf BLUE`

Interfaces, neighbors, topology entries, and routes belong to their selected context. Always name the context in your troubleshooting notes.

2. Build the Dual-Stack and VRF Lab

R1Global IPv4 + IPv6AS 100

Global link10.0.12.0/302001:db8:12::/64

R2Multiple contextsGlobal and VRF BLUE

VRF link10.20.23.0/30Isolated table

R3VRF BLUECustomer edge

Keep the global and VRF links separate so verification results are easy to interpret.

3. Read Named EIGRP Hierarchy

Named process

A local container, such as ENTERPRISE.

Address family

Chooses IPv4/IPv6, AS, and optional VRF.

AF interface

Holds interface-specific timers, authentication, and passive state.

Important: The process name is locally significant. The autonomous-system value is what participating neighbors must agree on.

4. Configure Global IPv4 Named Mode

router eigrp ENTERPRISE
 address-family ipv4 unicast autonomous-system 100
  eigrp router-id 1.1.1.1
  network 10.0.12.1 0.0.0.0
  network 10.10.10.1 0.0.0.0
 exit-address-family

The host-specific wildcard enables EIGRP only on the intended local interfaces. Verify the neighbor before checking remote routes.

5. Configure the IPv6 Address Family

ipv6 unicast-routing
router eigrp ENTERPRISE
 address-family ipv6 unicast autonomous-system 100
  eigrp router-id 1.1.1.1
  af-interface GigabitEthernet0/0
   no shutdown
  exit-af-interface
 exit-address-family

EIGRP for IPv6 uses link-local next hops and the multicast address FF02::A. A 32-bit router ID is still required even in an IPv6-only lab.

Version awareness: Exact IPv6 activation syntax can vary across IOS releases. Use context-sensitive help on the lab platform.

6. Create a VRF-Aware IPv4 Address Family

Create and attach VRF

vrf definition BLUE
 address-family ipv4
 exit-address-family
interface GigabitEthernet0/1
 vrf forwarding BLUE
 ip address 10.20.23.2 255.255.255.252

Enable EIGRP in BLUE

router eigrp ENTERPRISE
 address-family ipv4 unicast vrf BLUE autonomous-system 200
  eigrp router-id 2.2.2.2
  network 10.20.23.2 0.0.0.0
 exit-address-family

Order matters: Applying vrf forwarding commonly removes the existing IP address. Reapply addressing and verify connectivity before expecting an EIGRP neighbor.

7. Verify in the Correct Context

Question	Global command	VRF-aware command
Is the interface correct?	`show ip interface brief`	`show ip interface brief vrf BLUE`
Did the neighbor form?	`show ip eigrp neighbors`	`show ip eigrp vrf BLUE neighbors`
Was the path learned?	`show ip eigrp topology`	`show ip eigrp vrf BLUE topology`
Was the route installed?	`show ip route eigrp`	`show ip route vrf BLUE eigrp`

Command word order varies on some releases. The essential habit is to include the VRF whenever you inspect a VRF route.

8. Troubleshoot Context Mistakes

Symptom	Likely cause	First action
Ping works globally, not in VRF	Test used the wrong routing table	Use a VRF-aware ping
No IPv6 neighbor	IPv6 routing, interface activation, or router ID missing	Check IPv6 interface and AF status
VRF neighbor missing	Interface belongs to another context	Confirm VRF membership
Neighbor up, route absent globally	Route exists only in VRF	Inspect the VRF topology and route table
Adjacency rejected	AS, K-values, or authentication differs	Compare both address families

9. Migrate Safely from Classic to Named Mode

Record neighbors, topology entries, routes, and interface settings.
Translate router-level and interface-level commands into the named hierarchy.
Use a maintenance window because changing modes resets adjacencies.
Verify each address family independently.
Confirm routing and forwarding before removing rollback configuration.

Do not mix syntax from memory: Build the named-mode hierarchy first, then place each command at router, address-family, topology, or AF-interface level.

10. Guided Practice Lab

Global IPv4

Build one named IPv4 neighbor.
Advertise one loopback.
Verify neighbor, topology, and route.

Global IPv6

Enable IPv6 routing.
Set router IDs and activate interfaces.
Verify link-local next hops.

VRF BLUE

Create the VRF and attach interfaces.
Build a separate EIGRP AF.
Prove global and VRF tables stay isolated.

11. Treat Every Address Family as a Separate Failure Domain

A global IPv4 neighbor can be healthy while the IPv6 or VRF neighbor is down. Do not use success in one table as proof for another table.

Failure	What remains healthy	Correct response
VRF BLUE interface is down	Global IPv4 and IPv6 may continue	Inspect only the BLUE interface and address family first.
IPv6 router ID is missing	IPv4 address family may remain operational	Set a unique 32-bit router ID under IPv6 AF.
Global K-values mismatch	Separate VRF adjacency may remain up	Compare parameters inside the affected AF.
Route leaking policy fails	Neighbors inside each table can stay healthy	Inspect the boundary policy, not the adjacencies.

Useful habit: Begin every ticket with the protocol family, VRF name, interface, AS number, and failing prefix.

12. Apply Authentication to the Correct AF-Interface

Authentication belongs to the interface policy of an address family. Applying it to the global IPv4 interface does not automatically protect the IPv6 or VRF address family.

Global IPv4 AF-interface

router eigrp ENTERPRISE
 address-family ipv4 unicast autonomous-system 100
  af-interface GigabitEthernet0/0
   authentication mode md5
   authentication key-chain EIGRP-KEYS

VRF BLUE AF-interface

router eigrp ENTERPRISE
 address-family ipv4 unicast vrf BLUE autonomous-system 200
  af-interface GigabitEthernet0/1
   authentication mode md5
   authentication key-chain BLUE-KEYS

Both neighbors in the same context must use compatible authentication. Test one address family at a time so a mismatch is easy to isolate.

13. Read Operational Output Like a Troubleshooter

Neighbor table

Confirm peer address, interface, uptime, hold time, SRTT, RTO, and queue count.

Topology table

Confirm successor, feasible distance, reported distance, and Passive state.

Routing table

Confirm the route won installation inside the intended global or VRF RIB.

Observation	Meaning	Next question
Neighbor exists, topology prefix missing	Adjacency works but the prefix is not advertised	Does the source AF select that interface or network?
Topology prefix exists, route missing	EIGRP learned it but the RIB rejected or preferred another route	Which route source and administrative distance won?
Queue count stays above zero	Reliable EIGRP packets are waiting	Is there loss, congestion, or a slow peer?

14. Use a Production Validation Checklist

Document each address family, AS number, VRF, router ID, interfaces, and expected neighbors.
Verify IPv4, IPv6, and VRF reachability before enabling EIGRP.
Confirm passive interfaces, authentication, summaries, and redistribution per context.
Test one representative prefix from neighbor table through topology, RIB, CEF, and return path.
Save working output and a rollback plan before migrating classic configuration.

Route-leaking caution: A VRF exists to isolate routing. Import or export routes only with explicit ownership, prefix policy, tags, and return-path testing.

15. Frequently Asked Questions

Must the named EIGRP process name match?

No. It is locally significant. Neighbors must agree on the autonomous-system value and other adjacency requirements.

Can the same router run global and VRF EIGRP?

Yes. They are separate address-family contexts with separate neighbors, topology entries, and routing tables.

Why does EIGRP for IPv6 need an IPv4-style router ID?

The router ID is a 32-bit EIGRP identifier. It is not used as an IPv4 forwarding address.

Does a VRF route automatically enter the global table?

No. Moving routes between contexts requires an explicit, carefully controlled design such as route leaking or redistribution.

Can two address families use different AS numbers?

Yes. Each address family has its own autonomous-system setting. Only routers that need to become neighbors inside that context must agree.

Why is a route visible with a VRF command but not show ip route?

The route belongs to the VRF routing table. The normal show ip route command displays the global IPv4 table.