In which configuration mode is clear ip eigrp neighbors used?

The clear ip eigrp neighbors command is entered in Privileged EXEC mode on Cisco IOS devices.

EIGRPPrivileged EXEC

clear ip eigrp neighbors

This command immediately resets all EIGRP neighbor adjacencies, forcing the router to re-establish neighbor relationships and re-learn routes from all EIGRP neighbors.

Definition: clear ip eigrp neighbors is a Cisco IOS privileged exec command. This command immediately resets all EIGRP neighbor adjacencies, forcing the router to re-establish neighbor relationships and re-learn routes from all EIGRP neighbors.

Overview

The `clear ip eigrp neighbors` command is a powerful troubleshooting tool in Cisco IOS that immediately resets all EIGRP neighbor adjacencies. When executed, the router tears down all existing EIGRP neighbor relationships, clears the EIGRP topology table, and forces the router to re-discover neighbors and re-learn routes from scratch. This command is typically used in scenarios where EIGRP neighbor relationships are stuck, routes are not being exchanged correctly, or when you need to force a full route refresh without reloading the router.

It is important to note that this command does not affect the running configuration; it only clears dynamic state. The command requires privileged EXEC mode (enable mode) and may cause a temporary disruption in routing as neighbors are re-established. Unlike `clear ip eigrp neighbors *` (which clears all neighbors), the command without the asterisk clears all neighbors as well; the asterisk is optional but commonly used for emphasis.

Alternatives include `clear ip eigrp neighbors [interface]` to clear only neighbors on a specific interface, or `clear ip eigrp topology` to clear only the topology table without resetting adjacencies. In a broader workflow, this command is often used after changing EIGRP parameters (like K-values, timers, or authentication) that require a full reset to take effect. It is also used during troubleshooting when EIGRP routes are not converging or when a neighbor is stuck in the 'Init' state.

The command generates syslog messages indicating that neighbors are being reset, and the output is immediate. There is no buffered output; the command executes and returns to the prompt. The privilege level required is 15 (enable mode).

Syntax·Privileged EXEC

clear ip eigrp neighbors

When to Use This Command

After changing EIGRP configuration parameters (e.g., K-values, hold timers) that require neighbors to re-negotiate.
When troubleshooting EIGRP neighbor flapping or stuck-in-active (SIA) routes, to force a clean restart of neighbor relationships.
To quickly recover from a network event where EIGRP routes are stale or incorrect, without reloading the router.
During lab testing or network maintenance to simulate a full EIGRP reset and verify convergence.

Parameters

Parameter	Syntax	Required	Description
interface	interface-type interface-number	Optional	Specifies a particular interface (e.g., GigabitEthernet0/0) to clear only EIGRP neighbors on that interface. If omitted, all EIGRP neighbors are cleared. Common mistake: using the wrong interface name or number, or forgetting that the interface must be EIGRP-enabled.
neighbor-address	A.B.C.D	Optional	Specifies the IP address of a specific neighbor to clear. If used, only that neighbor adjacency is reset. This is useful for targeting a problematic neighbor without disrupting others. Common mistake: using an incorrect IP address or one that is not an EIGRP neighbor.

Command Examples

Basic EIGRP neighbor reset

clear ip eigrp neighbors

*Mar  1 00:05:23.123: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.2 (GigabitEthernet0/0) is down: cleared manually
*Mar  1 00:05:23.124: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.0.0.2 (GigabitEthernet0/1) is down: cleared manually
*Mar  1 00:05:28.456: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.2 (GigabitEthernet0/0) is up: new adjacency
*Mar  1 00:05:28.789: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.0.0.2 (GigabitEthernet0/1) is up: new adjacency

The output shows syslog messages indicating each neighbor going down due to manual clear, then coming back up after the hold timer expires and hello packets are exchanged. The format includes timestamp, DUAL state change, neighbor IP, interface, and reason.

Clear neighbors on a specific interface

clear ip eigrp neighbors GigabitEthernet0/0

*Mar  1 00:06:15.001: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.2 (GigabitEthernet0/0) is down: cleared manually
*Mar  1 00:06:20.234: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 192.168.1.2 (GigabitEthernet0/0) is up: new adjacency

Only the neighbor on the specified interface is reset. The output shows the neighbor going down and then up after re-establishing adjacency.

Understanding the Output

The command does not produce a direct table output; instead, it triggers syslog messages (if logging is enabled) that show DUAL neighbor state changes. Each message includes a timestamp, the DUAL process identifier, the AS number, the neighbor IP address, the interface, and the reason for the change (e.g., 'cleared manually' or 'new adjacency'). In a real network, you would monitor these messages to confirm that neighbors reset and re-establish.

After the clear, you can use 'show ip eigrp neighbors' to verify the neighbor table is repopulated. Good indicators are that all expected neighbors appear in the neighbor table with uptime counters resetting. Watch for neighbors that fail to come back up, which may indicate a configuration mismatch or connectivity issue.

Configuration Scenarios

Reset all EIGRP neighbors after changing K-values

After modifying EIGRP metric weights (K-values) on a router, the changes do not take effect until neighbor adjacencies are reset. This scenario clears all EIGRP neighbors to apply the new K-values.

Topology

R1(Gi0/0)---10.0.12.0/30---(Gi0/0)R2
R1(Gi0/1)---10.0.13.0/30---(Gi0/0)R3

Steps

1.Step 1: Enter privileged EXEC mode: R1> enable
2.Step 2: Verify current EIGRP neighbors: R1# show ip eigrp neighbors
3.Step 3: Clear all EIGRP neighbors: R1# clear ip eigrp neighbors
4.Step 4: Verify that neighbors are re-establishing: R1# show ip eigrp neighbors

Configuration

! No configuration change is made by this command; it only clears dynamic state.
! Ensure that K-values are already configured before clearing.
R1(config)# router eigrp 100
R1(config-router)# metric weights 0 1 0 1 0 0
R1(config-router)# end
R1# clear ip eigrp neighbors

Verify: R1# show ip eigrp neighbors Expected output: Neighbor table should repopulate with new adjacency information. Initially empty, then within a few seconds neighbors appear with state 'Init' then 'Established'.

Watch out: If K-values are changed without clearing neighbors, the old metric values continue to be used until the adjacency is reset. Also, ensure that all routers in the EIGRP domain have matching K-values; otherwise, neighbors will not form.

Clear a specific stuck EIGRP neighbor on a WAN link

A single EIGRP neighbor on a slow WAN link is stuck in the 'Init' state and not exchanging routes. Clearing only that neighbor avoids disrupting other stable adjacencies.

Topology

R1(Gi0/0)---192.168.1.0/30---(Gi0/0)R2
R1(Gi0/1)---10.0.0.0/30---(Gi0/0)R3

Steps

1.Step 1: Enter privileged EXEC mode: R1> enable
2.Step 2: Identify the problematic neighbor: R1# show ip eigrp neighbors
3.Step 3: Clear only that neighbor: R1# clear ip eigrp neighbors 192.168.1.2
4.Step 4: Monitor the neighbor re-establishment: R1# show ip eigrp neighbors

Configuration

! No configuration change.
R1# clear ip eigrp neighbors 192.168.1.2

Verify: R1# show ip eigrp neighbors Expected output: The neighbor 192.168.1.2 should initially disappear, then reappear with state 'Init' and quickly transition to 'Established'.

Watch out: If the neighbor is stuck due to a mismatch in EIGRP parameters (e.g., AS number, authentication), clearing alone will not fix the issue; you must correct the configuration first. Also, ensure you use the correct IP address of the neighbor, not the local interface IP.

Troubleshooting with This Command

When troubleshooting EIGRP neighbor issues, the `clear ip eigrp neighbors` command is a first-line tool to reset adjacencies that are stuck or not exchanging routes. Healthy output from `show ip eigrp neighbors` shows neighbors in 'Established' state with a hold time countdown and uptime. Problem indicators include neighbors stuck in 'Init' state, 'Pending' state, or 'Down' state.

If a neighbor is stuck in 'Init', it indicates that the router has sent a hello but not received a reply; clearing the neighbor can force a fresh hello exchange. If the neighbor is flapping (repeatedly going up and down), clearing may temporarily stabilize but the root cause (e.g., link instability, mismatched timers) must be addressed. A step-by-step diagnostic flow: 1) Check `show ip eigrp neighbors` to identify problem neighbors. 2) Verify EIGRP configuration with `show ip eigrp interfaces` and `show ip protocols`. 3) If a specific neighbor is problematic, clear only that neighbor with `clear ip eigrp neighbors [ip-address]`. 4) Immediately after clearing, use `debug eigrp packets` or `debug eigrp neighbors` to observe the hello and update exchange. 5) Check `show ip eigrp topology` to see if routes are being learned. 6) If the problem persists, check Layer 2 connectivity, ACLs, and authentication.

The command's output is minimal; it does not provide diagnostic information itself but triggers events that can be observed with other commands. Correlate with `show ip eigrp traffic` to see packet counts, and `show logging` for syslog messages like '%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.0.12.2 (GigabitEthernet0/0) is down: manually cleared'. This message confirms the clear action.

In complex scenarios, clearing all neighbors might be necessary if the router has a corrupted topology table; however, this should be done during a maintenance window as it causes a temporary routing blackout. Always document the state before clearing, as the command is irreversible in terms of dynamic state.

CCNA Exam Tips

The command 'clear ip eigrp neighbors' is in Privileged EXEC mode, not global configuration.

On the CCNA exam, know that this command resets all EIGRP neighbors; to reset a specific neighbor, use 'clear ip eigrp neighbors [interface-type number]'.

Be aware that clearing neighbors causes temporary route loss and may impact traffic; it should be used carefully in production.

The exam may test that this command triggers DUAL events and that you can verify neighbor re-establishment with 'show ip eigrp neighbors'.

Common Mistakes

Using 'clear ip eigrp neighbors' in global configuration mode instead of Privileged EXEC mode.

Forgetting that this command clears all neighbors, not just one; using it unnecessarily can cause network disruption.

Assuming the command provides immediate output; it only generates syslog messages, so you must check logs or use 'show' commands afterward.

clear ip eigrp neighbors vs show ip eigrp topology

These two EIGRP commands are often confused because both are used in troubleshooting EIGRP, but they serve opposite functions: one is a disruptive action that resets neighbor relationships, while the other is a diagnostic view of the topology table. Understanding their differences is critical for effective network troubleshooting.

Aspect	clear ip eigrp neighbors	show ip eigrp topology
Scope	All EIGRP neighbors on the router	All EIGRP routes in the topology table
Impact	Resets neighbor adjacencies and flushes routes	No impact; read-only display
Required Privilege	Privileged EXEC (enable mode)	Privileged EXEC (enable mode)
Typical Use Case	Recover from stuck-in-active or force re-convergence	Verify feasible successors and route paths
Data Source	Clears internal neighbor state	Reads the EIGRP topology database
Risk	Disruptive; causes temporary routing loss	None; safe to use at any time

Use clear ip eigrp neighbors when you need to forcefully reset all EIGRP neighbor relationships, typically to recover from a neighbor stuck-in-active event or to trigger immediate re-convergence.

Use show ip eigrp topology when you need to inspect the EIGRP topology table to verify learned routes, feasible successors, or convergence status without affecting network operations.

Platform Notes

In Cisco IOS-XE (e.g., 16.x and later), the `clear ip eigrp neighbors` command behaves identically to classic IOS. However, in IOS-XE, the command may be slightly slower on high-end platforms due to the control plane architecture. The syntax is the same.

In NX-OS (Cisco Nexus switches), the equivalent command is `clear ip eigrp neighbors` as well, but note that NX-OS uses a different EIGRP implementation; the command clears neighbors on the default VRF unless a VRF is specified. For example: `clear ip eigrp neighbors vrf RED`. In NX-OS, the command also supports the `interface` and `neighbor-address` parameters.

On Cisco ASA firewalls, EIGRP is not supported; the ASA uses OSPF or RIP for dynamic routing, so this command does not exist. In IOS-XR, the equivalent command is `clear eigrp neighbors` (without 'ip'), and it requires the 'router eigrp' context. For example: `RP/0/RP0/CPU0:router# clear eigrp neighbors *`.

IOS-XR also supports clearing by interface or neighbor address. In older IOS versions (12.x), the command is the same as in 15.x. One behavioral difference: in some IOS versions, clearing neighbors may also clear the topology table, while in others the topology table is cleared only if the neighbor is the only source for a route.

Always verify with `show ip eigrp topology` after clearing. In all platforms, the command requires privileged EXEC mode (enable) and does not affect the running configuration.

Related Commands

clear ip route *

Clears all entries from the IP routing table, forcing the router to rebuild the routing table from active routing protocols and directly connected networks.

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.

show ip eigrp topology

Displays the EIGRP topology table, showing all learned routes and their feasible successors, used to verify EIGRP convergence and path selection.

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