In which configuration mode is show ip eigrp topology used?

The show ip eigrp topology command is entered in Privileged EXEC mode on Cisco IOS devices.

EIGRPPrivileged EXEC

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.

Definition: show ip eigrp topology is a Cisco IOS privileged exec command. Displays the EIGRP topology table, showing all learned routes and their feasible successors, used to verify EIGRP convergence and path selection.

Overview

The 'show ip eigrp topology' command is a fundamental diagnostic tool for EIGRP (Enhanced Interior Gateway Routing Protocol) networks. It displays the EIGRP topology table, which contains all routes learned by the router, including feasible successors and the current best path. This command is essential for verifying EIGRP convergence, understanding path selection, and troubleshooting routing issues.

The topology table is the core of EIGRP's Diffusing Update Algorithm (DUAL), which ensures loop-free and fast convergence. Unlike the routing table (show ip route), which shows only the best paths, the topology table reveals all candidate paths, their metrics, and their status (passive or active). This allows network engineers to identify backup routes (feasible successors) and detect potential routing loops or stuck-in-active (SIA) conditions.

You would use this command when investigating why a particular route is not being installed in the routing table, when verifying load balancing across equal-cost paths, or when troubleshooting EIGRP neighbor issues. It is also critical for understanding EIGRP's metric calculations and for tuning route selection via offset-lists or variance. The command outputs a large amount of data, so it is often piped to 'include' or 'section' for filtering.

It requires privileged EXEC mode (enable) and does not affect the running configuration. In larger networks, the output can be extensive, so using specific parameters (like AS number or network prefix) is recommended to narrow results. This command is available in all IOS versions and is a staple for CCNA and CCNP candidates learning EIGRP's advanced features.

Syntax·Privileged EXEC

show ip eigrp topology

When to Use This Command

Troubleshooting missing routes in an EIGRP network by checking if the route is in the topology table.
Verifying feasible successor routes for fast convergence after a link failure.
Checking the metric and successor status for a specific prefix to understand path selection.
Monitoring EIGRP topology changes during network maintenance or after configuration changes.

Parameters

Parameter	Syntax	Required	Description
AS number	<1-65535>	Optional	Specifies the EIGRP autonomous system number. If omitted, the command shows topology for all EIGRP processes. Use this to filter output for a specific AS when multiple EIGRP processes are running.
network-prefix	A.B.C.D	Optional	The IP network prefix (e.g., 10.0.0.0) to display topology entries for that specific network. This is useful for focusing on a particular route without scrolling through the entire table.
prefix-length	A.B.C.D/length	Optional	The network prefix with subnet mask length (e.g., 10.0.0.0/8). This parameter filters the topology table to show only routes matching the exact prefix and length.
active	active	Optional	Displays only routes that are currently in active state (undergoing DUAL computation). This is crucial for troubleshooting stuck-in-active (SIA) conditions where routes are not converging.
all-links	all-links	Optional	Shows all routes, including those that are not feasible successors. By default, only feasible successors are displayed. This parameter reveals all possible next hops, even if they do not meet the feasibility condition.
detail	detail	Optional	Provides detailed output for each topology entry, including the original route information, metric components, and the source of the route. This is useful for in-depth analysis of metric calculations.
pending	pending	Optional	Displays routes that are pending a DUAL decision. This is rarely used but can help in debugging scenarios where updates are queued.
summary	summary	Optional	Shows a summary of the EIGRP topology table, including the number of routes, prefixes, and their status. This gives a high-level view of the EIGRP process health.
zero-successors	zero-successors	Optional	Displays routes that have no successors (i.e., routes that are not reachable). This is helpful for identifying routes that have been removed from the topology but are still present in the table.

Command Examples

Viewing the entire EIGRP topology table

show ip eigrp topology

IP-EIGRP Topology Table for AS(100)/ID(10.0.0.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 192.168.1.0/24, 1 successors, FD is 28160
        via 10.0.0.2 (28160/2816), GigabitEthernet0/0
        via 10.0.0.3 (30720/2816), GigabitEthernet0/1
P 10.0.0.0/8, 1 successors, FD is 28160
        via 10.0.0.2 (28160/2816), GigabitEthernet0/0
P 172.16.0.0/16, 1 successors, FD is 30720
        via 10.0.0.3 (30720/2816), GigabitEthernet0/1

Line 1: Shows AS number and router ID. 'P' means route is passive (stable). '192.168.1.0/24' is the destination network. '1 successors' indicates one best path. 'FD is 28160' is the feasible distance. Each 'via' line shows next-hop IP, (computed metric/reported distance), and outgoing interface.

Viewing topology for a specific network

show ip eigrp topology 192.168.1.0/24

IP-EIGRP topology entry for 192.168.1.0/24
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 28160
  Routing Descriptor Blocks:
  10.0.0.2 (GigabitEthernet0/0), from 10.0.0.2, Send flag is 0x0
      Composite metric is (28160/2816), Route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 200 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
  10.0.0.3 (GigabitEthernet0/1), from 10.0.0.3, Send flag is 0x0
      Composite metric is (30720/2816), Route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 300 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1

Shows detailed topology entry for a specific prefix. 'State is Passive' means route is stable. 'FD is 28160' is feasible distance. Each Routing Descriptor Block shows a path with next-hop IP, interface, composite metric (FD/RD), and vector metrics (bandwidth, delay, reliability, load, MTU, hop count). The path with lower metric (28160) is the successor.

Understanding the Output

The 'show ip eigrp topology' output lists all EIGRP-learned routes. Each entry starts with a code: 'P' (Passive) means the route is stable; 'A' (Active) means the router is actively querying for a route (potential issue). The destination network is followed by the number of successors (best paths) and the Feasible Distance (FD).

Each path shows the next-hop IP, the composite metric (FD/reported distance from neighbor), and the outgoing interface. The composite metric is calculated from bandwidth, delay, reliability, load, and MTU. A lower FD indicates a better path.

The reported distance (RD) is the distance advertised by the neighbor; for a route to be a feasible successor, the RD must be less than the FD. In a healthy network, all routes should be Passive. Active routes indicate convergence issues.

Watch for high metrics or multiple successors indicating load balancing.

Configuration Scenarios

Verify EIGRP Convergence After Adding a New Link

A network engineer has added a new redundant link between two branch routers to improve resilience. They need to verify that EIGRP has converged and that the new path appears as a feasible successor.

Topology

R1(Gi0/0)---10.0.12.0/30---(Gi0/0)R2
R1(Gi0/1)---10.0.13.0/30---(Gi0/1)R3
R2(Gi0/1)---10.0.23.0/30---(Gi0/1)R3

Steps

1.Step 1: Enter privileged EXEC mode: Router> enable
2.Step 2: Display the EIGRP topology table for the specific network: Router# show ip eigrp topology 192.168.1.0/24
3.Step 3: Verify that the new path appears as a feasible successor (indicated by 'via' with a metric and 'FD' value).
4.Step 4: Check the routing table to confirm the best path is installed: Router# show ip route 192.168.1.0

Configuration

! No configuration changes needed for verification; the command is used post-configuration.
! Example EIGRP configuration on R1:
router eigrp 100
 network 10.0.0.0
 network 192.168.1.0

Verify: Router# show ip eigrp topology 192.168.1.0/24 P 192.168.1.0/24, 1 successors, FD is 28160 via 10.0.12.2 (28160/28160), GigabitEthernet0/0 via 10.0.13.3 (28672/28160), GigabitEthernet0/1

Watch out: If the new link is not appearing, ensure that the interface is not passive under the EIGRP process and that the neighbor relationship has formed (check with 'show ip eigrp neighbors').

Troubleshoot a Missing Route in the Routing Table

A router is not installing a specific route in its routing table, even though the neighbor relationship is up. The engineer needs to check the EIGRP topology table to see if the route is present and why it is not being selected.

Topology

R1(Gi0/0)---10.0.12.0/30---(Gi0/0)R2
R2(Lo0)---192.168.2.0/24

Steps

1.Step 1: Enter privileged EXEC mode: Router> enable
2.Step 2: Display the EIGRP topology table for the missing network: Router# show ip eigrp topology 192.168.2.0/24
3.Step 3: Check if the route is present and its status (P for passive, A for active).
4.Step 4: If the route is active, wait for DUAL to complete or investigate why it is stuck.
5.Step 5: If the route is passive but not in the routing table, check the feasible distance (FD) and reported distance (RD) to see if the route is feasible.
6.Step 6: Verify the routing table: Router# show ip route 192.168.2.0

Configuration

! Example EIGRP configuration on R1:
router eigrp 100
 network 10.0.0.0
! Ensure no distribute-list is blocking the route.

Verify: Router# show ip eigrp topology 192.168.2.0/24 P 192.168.2.0/24, 1 successors, FD is 28160 via 10.0.12.2 (28160/28160), GigabitEthernet0/0 Router# show ip route 192.168.2.0 D 192.168.2.0/24 [90/28160] via 10.0.12.2, 00:12:34, GigabitEthernet0/0

Watch out: If the route is in the topology table but not in the routing table, check if the route is being filtered by a distribute-list or if the administrative distance is higher than another protocol's route.

Troubleshooting with This Command

When troubleshooting EIGRP, the 'show ip eigrp topology' command is invaluable for diagnosing route selection and convergence issues. A healthy output shows routes in passive state (P) with one or more successors and feasible successors. The key fields to examine are the route state (P for passive, A for active), the number of successors, the feasible distance (FD), and the reported distance (RD) from each neighbor.

If a route is in active state (A), it means DUAL is actively computing a new path, which can indicate a network change or a stuck-in-active (SIA) condition. SIA occurs when a query is not replied to within the active timer (default 3 minutes), causing the route to be stuck. To diagnose SIA, use 'show ip eigrp topology active' to see which routes are active and which neighbors have not replied.

Another common issue is a missing feasible successor. If a route has only one successor and that neighbor goes down, the route will go active and may become unreachable if no feasible successor exists. To check for feasible successors, use 'show ip eigrp topology all-links' to see all potential next hops, even those that do not meet the feasibility condition.

The feasibility condition requires that the RD from a neighbor is less than the FD of the current successor. If a route is not being installed in the routing table, compare the FD and RD values. If the RD is greater than or equal to the FD, the route is not a feasible successor and will not be used unless the current successor fails.

Additionally, metric mismatches can cause routes to be ignored. EIGRP uses bandwidth, delay, load, reliability, and MTU (by default only bandwidth and delay) to compute the metric. If the K values are mismatched between routers, routes may not be accepted.

Use 'show ip eigrp topology detail' to see the metric components. Another common symptom is load balancing not working as expected. By default, EIGRP supports up to 4 equal-cost paths.

To verify, check the number of successors in the topology table. If you expect unequal-cost load balancing (using variance), ensure that the variance command is configured and that the alternate paths meet the feasibility condition. Correlate the topology table with 'show ip eigrp neighbors' to confirm neighbor reachability and with 'show ip route eigrp' to see which routes are installed.

For deeper debugging, use 'debug eigrp fsm' to watch DUAL state transitions, but use with caution in production. In summary, the topology table is the first place to look when EIGRP routes are missing, not converging, or not load balancing as expected.

CCNA Exam Tips

CCNA exam tip: Remember that 'P' stands for Passive (stable) and 'A' for Active (querying). Active routes often appear in exam troubleshooting questions.

CCNA exam tip: The Feasible Distance (FD) is the metric of the best path; the Reported Distance (RD) is the metric advertised by the neighbor. For a feasible successor, RD must be less than FD.

CCNA exam tip: EIGRP uses DUAL algorithm; the topology table holds all routes, while the routing table only holds the successor(s).

CCNA exam tip: In the output, 'via' lines show all paths; the first one is usually the successor. Multiple successors indicate equal-cost load balancing.

Common Mistakes

Mistake 1: Confusing the topology table with the routing table. The topology table shows all EIGRP routes, while the routing table shows only the best routes installed.

Mistake 2: Ignoring the route state (Passive vs Active). An Active route indicates a query in progress, which can cause network instability.

Mistake 3: Misinterpreting the composite metric values. The metric is a composite of bandwidth and delay by default; other K-values may be used but are rare.

show ip eigrp topology vs show ip eigrp interfaces

Both 'show ip eigrp topology' and 'show ip eigrp interfaces' are essential for EIGRP verification, but they serve distinct purposes: the former focuses on the routing table's state and path selection, while the latter examines interface-level participation and neighbor adjacency. They are often used together during troubleshooting, leading to confusion about which command to use for a specific need.

Aspect	show ip eigrp topology	show ip eigrp interfaces
Scope	EIGRP topology table (all learned routes)	EIGRP-enabled interfaces and their status
Primary Data	Routes, feasible successors, metric components	Interface IP, neighbor count, pending routes, uptime
Typical Use	Verify route availability and path selection	Confirm adjacency and interface participation
Output Focus	Network-layer routing information	Interface-level and data-link layer details
Dependency	Requires at least one EIGRP neighbor and route	Available if EIGRP is configured on any interface

Use show ip eigrp topology when you need to check which routes are in the EIGRP topology table, verify feasible successors, or diagnose path selection issues.

Use show ip eigrp interfaces when you need to confirm which interfaces are running EIGRP, verify neighbor adjacency status, or identify interface-level issues affecting EIGRP.

Platform Notes

In IOS-XE (e.g., Catalyst 9000 switches, ISR 4000 series), the 'show ip eigrp topology' command behaves identically to classic IOS, but the output may include additional fields such as 'Uptime' and 'Outgoing interface' in some versions. The syntax is the same. In NX-OS (e.g., Nexus 9000), the equivalent command is 'show ip eigrp topology' as well, but NX-OS uses a different EIGRP implementation (named mode only).

The output format is similar but may not include the 'all-links' parameter; instead, use 'show ip eigrp topology detail' to see all routes. NX-OS also supports 'show ip eigrp topology summary' for a high-level view. For ASA firewalls, EIGRP is not supported; ASAs use routing protocols like OSPF or BGP.

In IOS-XR (e.g., ASR 9000), EIGRP is not supported; IOS-XR uses OSPF, IS-IS, or BGP. Therefore, this command is not available on IOS-XR. Between IOS versions, the output has remained largely consistent from 12.x to 16.x, but newer versions may show additional details like 'Tag' or 'Route-map' information.

Always use the '?' help to confirm available parameters on your specific platform.

Related Commands

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.

show ip protocols

Displays the current state of all IP routing protocols running on the router, including timers, filters, and network advertisements.

show ip route

Displays the IP routing table showing all known routes, their source protocols, administrative distances, metrics, next-hops, and outgoing interfaces.

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