network [ip] [wildcard]
Enables EIGRP on a network interface by specifying the directly connected network and optional wildcard mask to control which interfaces participate in EIGRP.
Definition: network [ip] [wildcard] is a Cisco IOS router config command. Enables EIGRP on a network interface by specifying the directly connected network and optional wildcard mask to control which interfaces participate in EIGRP.
Overview
The 'network' command in EIGRP configuration mode is the fundamental mechanism for enabling the EIGRP routing process on a router's interfaces. It specifies which directly connected networks will be advertised to EIGRP neighbors and which interfaces will participate in forming adjacencies. This command is critical because EIGRP, unlike some other routing protocols, does not automatically enable on all interfaces; you must explicitly define the networks that should run EIGRP.
The command uses a combination of an IP address and an optional wildcard mask to match interfaces. The wildcard mask, often misunderstood, is the inverse of a subnet mask: bits set to 0 must match exactly, bits set to 1 are ignored. For example, 10.0.0.0 0.255.255.255 matches any interface with an IP starting with 10.
This flexibility allows engineers to enable EIGRP on a single interface, a subnet, or an entire major network. The command is typically used during initial EIGRP configuration or when adding new networks to an existing EIGRP domain. Alternatives include using the 'passive-interface' command to suppress hello packets on specific interfaces while still advertising the network, or using route summarization to control advertisement scope.
In the broader workflow, after configuring EIGRP with the 'router eigrp' command, you use 'network' to define participating interfaces, then optionally tune parameters like bandwidth, delay, or authentication. Important IOS behavior: the 'network' command immediately affects the running configuration; EIGRP will start sending hello packets out matched interfaces. The command requires global configuration mode (configure terminal) and privilege level 15.
There is no buffered output; changes take effect instantly. Understanding wildcard masks is crucial: a common mistake is using a subnet mask instead of a wildcard mask, which can lead to unintended interface participation or failure to form adjacencies. This command is foundational for EIGRP operation and appears in both CCNA and CCNP curricula.
network [ip] [wildcard]When to Use This Command
- Enable EIGRP on a LAN segment connected to a router interface, e.g., 192.168.1.0/24.
- Use a wildcard mask to advertise a specific subnet within a larger network, e.g., 10.0.0.0 0.0.0.255.
- Enable EIGRP on a point-to-point WAN link by specifying the exact IP of the serial interface.
- Advertise a loopback interface network for OSPF-like routing stability.
Parameters
| Parameter | Syntax | Description |
|---|---|---|
| ip | A.B.C.D | The IP address of the directly connected network. This can be a specific interface IP, a subnet address, or a major network address. The router will match this address against interface IPs using the wildcard mask. Common mistake: using a host IP instead of a network address; for example, using 10.0.0.1 instead of 10.0.0.0. |
| wildcard | A.B.C.D | The wildcard mask that determines which bits of the 'ip' parameter must match. Bits set to 0 must match exactly; bits set to 1 are ignored. If omitted, the default wildcard mask is 0.0.0.0, meaning the IP must match exactly (host route). Common mistake: using a subnet mask (e.g., 255.255.255.0) instead of the inverse (0.0.0.255). |
Command Examples
Enable EIGRP on a Class C network
network 192.168.1.0This command enables EIGRP on all interfaces whose IP address falls within the 192.168.1.0/24 network. No wildcard mask is specified, so the default classful mask (255.255.255.0) is used. Any interface with an IP in this range will start sending and receiving EIGRP updates.
Enable EIGRP with a wildcard mask for a specific subnet
network 10.0.0.0 0.0.0.255This command enables EIGRP only on interfaces that have an IP address in the 10.0.0.0/24 range. The wildcard mask 0.0.0.255 matches the last octet exactly. This is useful when you want to advertise a specific subnet within a larger classful network.
Understanding the Output
The 'network' command does not produce direct output. Instead, it configures the router to include the specified network in EIGRP updates. To verify, use 'show ip eigrp interfaces' to see which interfaces are participating, or 'show ip route eigrp' to see learned routes.
A correctly configured network will show the interface in the EIGRP neighbor table and the network in the routing table.
Configuration Scenarios
Enable EIGRP on a single subnet between two routers
Two routers, R1 and R2, are connected via a point-to-point link on subnet 10.0.12.0/30. The goal is to enable EIGRP AS 100 on both routers so they exchange routes over this link.
Topology
R1(Gi0/0)---10.0.12.0/30---(Gi0/0)R2Steps
- 1.Step 1: Enter global configuration mode on R1: R1> enable, then R1# configure terminal
- 2.Step 2: Enter EIGRP configuration mode: R1(config)# router eigrp 100
- 3.Step 3: Enable EIGRP on the subnet: R1(config-router)# network 10.0.12.0 0.0.0.3
- 4.Step 4: Repeat steps on R2 with the same AS number and network statement.
! R1(config)# router eigrp 100 R1(config-router)# network 10.0.12.0 0.0.0.3 ! R2(config)# router eigrp 100 R2(config-router)# network 10.0.12.0 0.0.0.3
Verify: Use 'show ip eigrp neighbors' on either router to see the adjacency. Expected output shows a neighbor entry with the other router's IP address and state 'Init' then 'Established'.
Watch out: Forgetting to include the wildcard mask and using 'network 10.0.12.0' alone will match only the exact IP 10.0.12.0, which is not an interface IP, so EIGRP will not enable on the link. Always use the correct wildcard mask for the subnet.
Enable EIGRP on multiple interfaces using a single network statement
A router has three interfaces: Gi0/0 (10.1.1.1/24), Gi0/1 (10.1.2.1/24), and Gi0/2 (192.168.1.1/24). The goal is to enable EIGRP on all interfaces in the 10.1.0.0/16 range without enabling it on the 192.168.1.0/24 interface.
Topology
R1: Gi0/0 (10.1.1.1/24), Gi0/1 (10.1.2.1/24), Gi0/2 (192.168.1.1/24)Steps
- 1.Step 1: Enter EIGRP configuration mode: R1(config)# router eigrp 100
- 2.Step 2: Use a wildcard mask that matches all 10.1.x.x interfaces: R1(config-router)# network 10.1.0.0 0.0.255.255
- 3.Step 3: Optionally, use a separate network statement for the 192.168.1.0/24 if needed, or leave it out.
! R1(config)# router eigrp 100 R1(config-router)# network 10.1.0.0 0.0.255.255
Verify: Use 'show ip eigrp interfaces' to see which interfaces are participating. Expected output lists Gi0/0 and Gi0/1 but not Gi0/2.
Watch out: Using a wildcard mask that is too broad (e.g., 0.0.0.0) might accidentally enable EIGRP on unwanted interfaces. Always verify the wildcard mask matches only the intended networks.
Troubleshooting with This Command
When troubleshooting EIGRP adjacency issues, the 'network' command is often the first place to look. A healthy EIGRP configuration will have network statements that exactly match the subnet of the interface IP. For example, if an interface has IP 10.0.12.2/30, the network statement should be 'network 10.0.12.0 0.0.0.3'.
If the wildcard mask is incorrect, the interface may not be enabled for EIGRP. Use 'show ip eigrp interfaces' to verify which interfaces are participating. If an interface is missing, check the network statement and wildcard mask.
Another common issue is using a network statement that matches the interface IP but with a wildcard mask that is too specific (e.g., 'network 10.0.12.2 0.0.0.0') which only matches that exact host IP, not the subnet. This will enable EIGRP on the interface but may cause route advertisement issues because the network advertised is a host route. To diagnose, use 'show ip eigrp topology' to see what networks are being advertised.
If you see a /32 route for the interface IP, the network statement is likely using a host mask. The correct approach is to use the subnet address with the appropriate wildcard mask. Additionally, if EIGRP neighbors are not forming, verify that both routers have matching AS numbers and that the network statements are correct on both ends.
Use 'debug eigrp packets' to see if hello packets are being sent and received. If hellos are not sent, the interface is not enabled for EIGRP. Correlate 'show ip eigrp interfaces' with 'show ip interface brief' to ensure the interface is up/up.
Also, check for passive interfaces: if an interface is set to passive, it will not send hellos, even if the network statement matches. Use 'show ip protocols' to see which interfaces are passive. In summary, the 'network' command is the gatekeeper for EIGRP participation; incorrect configuration here will prevent adjacencies and route exchange.
Always verify with 'show ip eigrp interfaces' and 'show ip eigrp neighbors'.
CCNA Exam Tips
CCNA exam tip: Remember that the 'network' command uses a wildcard mask, not a subnet mask. The wildcard is the inverse of the subnet mask.
CCNA exam tip: If no wildcard mask is specified, the router assumes the classful mask (e.g., /8 for Class A, /16 for Class B, /24 for Class C).
CCNA exam tip: The 'network' command does not need to match the exact IP of the interface; it matches the network portion. For example, 'network 192.168.1.0' will match any interface with an IP starting with 192.168.1.x.
CCNA exam tip: EIGRP uses the 'network' command to determine which interfaces to enable EIGRP on, not to advertise routes. The actual routes advertised are the networks connected to those interfaces.
Common Mistakes
Mistake 1: Using a subnet mask instead of a wildcard mask (e.g., 255.255.255.0 instead of 0.0.0.255). This will cause the command to be rejected or behave unexpectedly.
Mistake 2: Forgetting to include the 'network' command for all directly connected networks that should be advertised, leading to missing routes.
Mistake 3: Using a wildcard mask that is too broad, enabling EIGRP on unintended interfaces and potentially causing routing loops.
network [ip] [wildcard] vs router eigrp [as-number]
Both commands are essential for EIGRP configuration but operate at different levels. The `router eigrp` command initiates the EIGRP process and enters router configuration mode, while the `network` command is used within that mode to specify which interfaces will advertise and form neighbors. They are often confused because the `network` command is only valid after the `router eigrp` command, making them interdependent.
| Aspect | network [ip] [wildcard] | router eigrp [as-number] |
|---|---|---|
| Configuration Mode | Executed within router eigrp subconfig mode | Executed in global configuration mode |
| Purpose | Enables EIGRP on interfaces matching the IP and wildcard | Creates an EIGRP routing process with a unique AS number |
| Scope | Selectively enables EIGRP on specific networks | Defines the autonomous system globally |
| Dependency | Requires an existing router eigrp process | Independent; can be configured first |
| Multiple Instances | Multiple network statements allowed per process | Each AS number starts a separate process |
| Effect on Interfaces | Directly controls which interfaces run EIGRP | No direct interface impact; sets process parameters |
Use network [ip] [wildcard] when you need to activate EIGRP on specific directly connected interfaces to participate in route exchange.
Use router eigrp [as-number] when you need to start an EIGRP routing process and enter the configuration mode to define parameters like networks, timers, or metrics.
Platform Notes
In IOS-XE (e.g., Catalyst 9000 series), the 'network' command syntax is identical to classic IOS. However, IOS-XE uses the same EIGRP implementation, so no syntax differences. In NX-OS (e.g., Nexus switches), EIGRP configuration is similar but uses 'router eigrp <as-number>' and 'network <ip> <wildcard>' commands.
However, NX-OS also supports 'address-family ipv4 unicast' under the router configuration, and the network command is entered under the address-family. For example: 'router eigrp 100', 'address-family ipv4 unicast', 'network 10.0.12.0 0.0.0.3'. NX-OS also requires the 'feature eigrp' command to enable the EIGRP feature globally.
In ASA firewalls, EIGRP is not supported; ASAs use OSPF or RIP. In IOS-XR, EIGRP is not supported; IOS-XR uses OSPF, ISIS, or BGP. For IOS versions, the 'network' command has remained consistent from 12.x through 16.x.
However, in IOS 15.x and later, EIGRP supports named mode configurations, but the network command under the router eigrp process remains the same. In summary, the command is stable across IOS versions, but NX-OS requires an additional address-family context.
Related Commands
router eigrp [as-number]
Enters EIGRP router configuration mode for a specific autonomous system number, allowing you to configure EIGRP routing protocol parameters.
show ip eigrp interfaces
Displays detailed information about interfaces on which EIGRP is enabled, including neighbor status, pending routes, and interface statistics, used to verify EIGRP adjacency and interface participation.
show ip eigrp neighbors
Displays all EIGRP neighbours with their addresses, interfaces, hold time, uptime, SRTT (smooth round-trip time), RTO, queue count, and sequence numbers.
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