In which configuration mode is show etherchannel summary used?

The show etherchannel summary command is entered in Privileged EXEC mode on Cisco IOS devices.

EtherChannelPrivileged EXEC

show etherchannel summary

Displays the status and configuration of all EtherChannel interfaces on the switch, used to verify channel bundling, port membership, and protocol state.

Definition: show etherchannel summary is a Cisco IOS privileged exec command. Displays the status and configuration of all EtherChannel interfaces on the switch, used to verify channel bundling, port membership, and protocol state.

Overview

The 'show etherchannel summary' command is a critical diagnostic tool for any network engineer working with Cisco switches. It provides a concise, one-line-per-channel view of all EtherChannel interfaces configured on the device, including their port-channel interface number, protocol (LACP, PAgP, or static), bundle state (up/down), and the member ports with their individual status. This command is essential for verifying that link aggregation is functioning correctly, ensuring that multiple physical links are properly bundled into a single logical interface for increased bandwidth and redundancy.

The concept behind EtherChannel is to combine up to eight physical Ethernet links into one logical link, providing load balancing and failover. Without this command, an engineer would have to check each physical interface individually and cross-reference port-channel configurations, which is inefficient. Alternatives like 'show etherchannel port' or 'show etherchannel detail' provide more granular information but are less suitable for a quick overview.

In a typical troubleshooting workflow, after configuring an EtherChannel, you would immediately use this command to confirm the bundle is up and all member ports are active. If a bundle is down, you would then drill into 'show etherchannel detail' or 'show interfaces port-channel x' to investigate. Important IOS behavior: the output is buffered, so if you have many channels, you may need to use 'terminal length 0' to see all output.

The command requires privileged EXEC mode (enable). It does not affect the running configuration; it is purely a show command. The output includes flags like 'SU' (layer2 up), 'SD' (layer2 down), 'P' (bundled in port-channel), 'S' (standalone), 'D' (down), and 'U' (up).

Understanding these flags is key to rapid troubleshooting. For CCNA and CCNP candidates, mastering this command is vital for both exams and real-world network management, as EtherChannel is a fundamental technology for high-availability campus networks.

Syntax·Privileged EXEC

show etherchannel summary

When to Use This Command

Verify that a newly configured EtherChannel is up and all member ports are bundled correctly.
Troubleshoot why an EtherChannel is not forming, e.g., mismatched port parameters or protocol.
Check the load-balancing method or the number of active ports in a production environment.
Monitor the EtherChannel status after a link failure to confirm failover behavior.

Command Examples

Basic EtherChannel Summary

show etherchannel summary

Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      N - not in use, no aggregation
        f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+---------------------------------------------
1      Po1(SU)        LACP      Gi0/0(P)    Gi0/1(P)    Gi0/2(P)    Gi0/3(P)
2      Po2(SU)        PAgP      Gi0/4(P)    Gi0/5(P)    Gi0/6(P)    Gi0/7(P)

Line 1: Flags legend defines status codes. Line 2: Shows 2 channel-groups in use. Line 3: Group 1 uses LACP, Po1 is Layer2 (S) and in use (U), all 4 ports bundled (P). Group 2 uses PAgP, Po2 also Layer2 and in use, all 4 ports bundled.

EtherChannel with Suspended Ports

show etherchannel summary

Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      N - not in use, no aggregation
        f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+---------------------------------------------
1      Po1(SU)        LACP      Gi0/0(P)    Gi0/1(s)    Gi0/2(P)    Gi0/3(P)

Port Gi0/1 shows (s) indicating suspended. This usually happens due to mismatched port parameters (speed, duplex, VLAN) or LACP configuration. The other three ports are bundled (P). The channel is still up but with reduced bandwidth.

Understanding the Output

The output begins with a legend explaining flags: D (down), P (bundled), I (stand-alone), s (suspended), H (Hot-standby for LACP), R (Layer3), S (Layer2), U (in use), N (not in use), f (failed to allocate aggregator), M (minimum links not met), u (unsuitable), w (waiting), d (default). The summary shows the number of channel-groups and aggregators. The table lists each group number, port-channel interface with flags in parentheses (e.g., Po1(SU) means Layer2, in use), protocol (LACP or PAgP), and member ports with their status flags.

Key things to check: all member ports should show (P) for bundled; any (s) indicates a problem; (D) means down; (I) means not part of any channel. The protocol column should match on both sides of the link. A healthy EtherChannel shows all ports bundled and the port-channel interface up (U).

Configuration Scenarios

Verify LACP EtherChannel between two switches

After configuring a LACP EtherChannel between SwitchA and SwitchB, you need to confirm the bundle is operational and all member ports are active.

Topology

SwitchA(Gi0/1-2)---(Gi0/1-2)SwitchB

Steps

1.Step 1: Enter privileged EXEC mode on SwitchA: SwitchA> enable
2.Step 2: Run the command: SwitchA# show etherchannel summary
3.Step 3: Look for the port-channel number (e.g., Po1) with flags 'SU' (layer2 up) and member ports showing 'P' (bundled).
4.Step 4: Verify that the number of bundled ports matches the configuration (e.g., 2 ports).

Configuration

! On SwitchA
interface Port-channel1
 switchport mode trunk
!
interface GigabitEthernet0/1
 channel-group 1 mode active
!
interface GigabitEthernet0/2
 channel-group 1 mode active
!
! On SwitchB
interface Port-channel1
 switchport mode trunk
!
interface GigabitEthernet0/1
 channel-group 1 mode passive
!
interface GigabitEthernet0/2
 channel-group 1 mode passive

Verify: SwitchA# show etherchannel summary Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use N - not in use, no aggregation f - failed to allocate aggregator Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SU) LACP Gi0/1(P) Gi0/2(P)

Watch out: Ensure both sides use compatible LACP modes (active/passive or active/active). If one side is set to 'on' (static) and the other to LACP, the bundle will not form.

Troubleshoot a PAgP EtherChannel with a down member port

A PAgP EtherChannel between two Cisco switches has a member port that is down, causing reduced bandwidth. You need to identify the problematic port.

Topology

SwitchC(Gi0/1-3)---(Gi0/1-3)SwitchD

Steps

1.Step 1: Enter privileged EXEC mode on SwitchC: SwitchC> enable
2.Step 2: Run: SwitchC# show etherchannel summary
3.Step 3: Observe the flags for each member port. A 'D' flag indicates the port is down.
4.Step 4: Note the port with 'D' flag (e.g., Gi0/3) and investigate further with 'show interfaces Gi0/3' or 'show etherchannel 1 detail'.

Configuration

! On SwitchC
interface Port-channel1
 switchport mode trunk
!
interface GigabitEthernet0/1
 channel-group 1 mode desirable
!
interface GigabitEthernet0/2
 channel-group 1 mode desirable
!
interface GigabitEthernet0/3
 channel-group 1 mode desirable
!
! On SwitchD
interface Port-channel1
 switchport mode trunk
!
interface GigabitEthernet0/1
 channel-group 1 mode auto
!
interface GigabitEthernet0/2
 channel-group 1 mode auto
!
interface GigabitEthernet0/3
 channel-group 1 mode auto

Verify: SwitchC# show etherchannel summary Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use N - not in use, no aggregation f - failed to allocate aggregator Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SU) PAgP Gi0/1(P) Gi0/2(P) Gi0/3(D)

Watch out: A down port could be due to physical issues (cable, speed/duplex mismatch) or configuration mismatch (e.g., different allowed VLANs on trunk). Always check the physical interface status first.

Troubleshooting with This Command

When troubleshooting EtherChannel issues, 'show etherchannel summary' is your first line of defense. Healthy output shows the port-channel interface with flags 'SU' (Layer2 up) or 'RU' (Layer3 up), and all member ports listed with 'P' (bundled). The protocol column indicates whether LACP or PAgP is used.

Problem indicators include: a port-channel flag of 'SD' (Layer2 down) or 'RD' (Layer3 down), member ports with 'D' (down), 'I' (stand-alone), 's' (suspended), or 'H' (hot-standby). Common symptoms: if a member port shows 'I', it means the port is not receiving protocol messages from the peer, often due to misconfiguration or incompatible modes. A 's' flag indicates the port has been suspended by the protocol, typically due to link failures or configuration mismatches.

A 'H' flag (LACP only) means the port is in hot-standby mode because the maximum number of active ports has been reached. The diagnostic flow: 1) Run 'show etherchannel summary' to get an overview. 2) If a bundle is down, check the port-channel interface state with 'show interfaces port-channel x'. 3) If member ports are down, check physical interfaces with 'show interfaces status' or 'show interfaces x'. 4) If member ports are stand-alone or suspended, verify that both sides use the same protocol (LACP or PAgP) and compatible modes (active/passive for LACP, desirable/auto for PAgP). Also check for VLAN consistency on trunk ports. 5) Use 'show etherchannel detail' to see detailed protocol state and counters. 6) Correlate with 'debug etherchannel' or 'debug lacp' (with caution in production) to see real-time negotiations.

For load-balancing issues, use 'show etherchannel load-balance' to verify the hash algorithm. Remember that 'show etherchannel summary' does not show the load-balancing method; that requires a separate command. Also, if the output is truncated, use 'terminal length 0' to display all lines.

In summary, this command quickly reveals the health of all EtherChannels and directs further troubleshooting efforts.

CCNA Exam Tips

CCNA exam often tests the meaning of flags: (SU) means Layer2 and in use, (RU) means Layer3 and in use.

Remember that LACP uses the same system priority to determine which side controls the channel; mismatched priorities can cause issues.

A suspended port (s) is often due to mismatched speed, duplex, or VLAN configuration; the exam may ask you to identify the cause.

PAgP is Cisco proprietary; LACP is IEEE 802.3ad standard; know the difference for the exam.

Common Mistakes

Mistake: Assuming all ports in the channel are automatically bundled; forgetting to check for mismatched port parameters like speed or duplex.

Mistake: Confusing the flags (s) suspended with (D) down; suspended means the port is administratively up but not bundled due to configuration mismatch.

Mistake: Not verifying that the protocol (LACP/PAgP) matches on both ends; mismatched protocols prevent channel formation.

show etherchannel summary vs show etherchannel port

Both 'show etherchannel summary' and 'show etherchannel port' are privileged EXEC commands used for troubleshooting EtherChannel configurations, but they focus on different aspects: summary provides a high-level overview of all bundles, while port dives into detailed per-port status within a bundle. They are often confused because both display channel-related information, yet serve distinct diagnostic purposes.

Aspect	show etherchannel summary	show etherchannel port
Scope	All EtherChannels on the switch	All ports in all EtherChannels (or specific bundle)
Output detail	Brief per-channel: group, state, ports, protocol	Detailed per-port: state, aggregator ID, partner info, counters
Typical use	Quick health check of all bundles	In-depth troubleshooting of a specific bundle
Protocol info	Only protocol type (LACP or PAgP)	Protocol-specific details like partner system ID, port key
Port membership	List of member ports per channel	Status and flags for each port in a bundle

Use 'show etherchannel summary' when you need a quick overview of all EtherChannels, their operational status, and which ports are members.

Use 'show etherchannel port' when you need to diagnose a specific bundle issue, such as port role mismatches or protocol negotiation details.

Platform Notes

In IOS-XE (e.g., Catalyst 3650/3850, ISR 4000), the 'show etherchannel summary' command syntax and output are identical to classic IOS. However, on newer platforms, the output may include additional flags like 'F' for forwarding or 'B' for blocked in some software versions. On NX-OS (e.g., Nexus 9000), the equivalent command is 'show port-channel summary' or 'show port-channel database'.

The output format is different: it shows the port-channel interface, status, and member ports with flags like 'P' (up) or 'D' (down). NX-OS also supports 'show lacp neighbor' and 'show pagp neighbor' for protocol-specific details. For ASA firewalls, EtherChannel is called 'port-channel' and the command is 'show port-channel summary' (similar to NX-OS).

ASA does not support PAgP; only LACP or static. In IOS-XR (e.g., ASR 9000), the command is 'show ethernet bundle summary' or 'show bundle summary'. The concept is similar but terminology differs: 'bundle' instead of 'port-channel'.

IOS versions 12.x and 15.x have consistent output, but 16.x (IOS-XE 16.x) may show slightly different formatting, such as additional columns for 'Flags' or 'Ports'. Always check the specific platform documentation for exact flag meanings. For CCNA/CCNP, focus on classic IOS and IOS-XE, as NX-OS and IOS-XR are covered in more advanced certifications.

Related Commands

show etherchannel port

Displays detailed port-level information for all ports that are part of an EtherChannel bundle, including port state, aggregation protocol, and partner details.

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