Cisco NX-OS/IOS Port-Channel Comparison
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Objective
This tech note outlines the main differences in Port-Channel support between Cisco® NX-OS Software and Cisco IOS® Software. Sample configurations are included for Cisco NX-OS and Cisco IOS Software for some common features to demonstrate the similarities and differences. Please refer to the NX-OS documentation on Cisco.com for a complete list of supported features.
Port-Channel Overview
Port-Channels provide a mechanism for aggregating multiple physical Ethernet links into a single logical Ethernet link. Port-Channels are typically used to increase availability and bandwidth, while simplifying the network topology. Port-Channels can be configured in Static Mode (no protocol) or in conjunction with a protocol such as LaCP defined in IEEE 802.3ad or PaGP for dynamic negotiations and keep-alive detection for failover.
Important Cisco NX-OS and Cisco IOS Software Differences
In Cisco NX-OS:
- 256 Port-Channels are supported per chassis
- LaCP and Static Mode Port-Channels are supported (PaGP is not supported in Cisco NX-OS Software).
- LaCP command-line interface (CLI) configuration and verification commands are not available until you enable the LaCP feature with the feature lacp command.
- The CLI syntax for specifying multiple interfaces is different in Cisco NX-OS Software. The range keyword has been omitted from the syntax (IE: interface ethernet 1/1-2)
- A Port-Channel can be converted between a layer-2 and layer-3 Port-Channel without removing the member ports.
- The force keyword can be used when adding an interface to an existing Port-Channel to force the new interface to inherit all of the existing Port-Channel compatibility parameters.
Things You Should Know
The following list provides some additional facts about the Cisco NX-OS that should be helpful when designing, configuring, and maintaining a network using Port-Channels.
- A single Port-Channel cannot connect to two different VDCs in the same chassis.
- You cannot disable LaCP with the no feature lacp command if LaCP is configured for a Port-Channel. LaCP must be disabled on all Port-Channels prior to disabling LaCP globally.
- The show port-channel compatibility-parameters CLI command is very useful for verifying interface parameters when configuring Port-Channels.
Configuration Comparison
The following sample code shows configuration similarities and differences between the Cisco NX-OS and Cisco IOS Software CLIs. The CLI is very similar between Cisco IOS and Cisco NX-OS. Cisco NX-OS does not use the range keyword when specifying multiple interfaces. Cisco NX-OS also has the ability to force an interface to inherit existing Port-Channel compatibility parameters using the force keyword.
| Cisco IOS CLI | Cisco NX-OS CLI | |
|---|---|---|
| Enabling the LaCP Feature |
| Cisco IOS Software does not have the ability to enable or disable LaCP. | feature lacp |
|---|
| Configuring LACP Active Mode |
| interface range gigabitethernet 1/1-2
channel-group 1 mode active | interface ethernet 1/1-2
channel-group 1 mode active |
|---|
| Configuring LaCP Passive Mode |
| interface range gigabitethernet 1/1-2
channel-group 1 mode passive | interface ethernet 1/1-2
channel-group 1 mode passive |
|---|
| Configuring Static Mode (no protocol) |
| interface range gigabitethernet 1/1-2
channel-group 1 mode on | interface ethernet 1/1-2
channel-group 1 mode on |
|---|
| Enabling a Port Channel |
| interface port-channel 1
no shutdown | interface port-channel 1
no shutdown |
|---|
| Layer-2 Port-Channel Example |
| interface range gigabitethernet 1/1-2
switchport channel-group 1 mode active
no shutdown | interface ethernet 1/1-1
switchport channel-group 1 mode active
no shutdown |
|---|
| Layer-3 Port-Channel Example |
| interface range gigabitethernet 1/1-2
no switchport channel-group 1 mode active
ip address 192.168.1.1 255.255.255.0 no shutdown | interface ethernet 1/1-1
no switchport channel-group 1 mode active
ip address 192.168.1.1/32 no shutdown |
|---|
| Adding an Interface to an Existing Port-Channel |
| Cisco IOS Software does not have the force option, so all interface parameters have to be compatible prior to adding the interface to an existing Port-Channel.
no switchport channel-group 1 mode active[ | interface ethernet 1/3
channel-group 1 force mode active |
|---|
| Configuring the System Load-Balance Algorithm |
| port-channel load-balance dst-mac | port-channel load-balance ethernet destination-mac |
|---|
| Configuring the Load-Balance Algorithm per Module |
| port-channel per-module load-balance
port-channel load-balance dst-mac module 1 | port-channel load-balance ethernet destination-mac module 1 |
|---|
Verification Command Comparison
The following table lists some useful show commands for verifying and troubleshooting a Port-Channel configuration.
| Cisco NX-OS Port-Channels | Cisco IOS Software Port-Channels | Command Description |
|---|---|---|
| show interface | show interface | Displays statistics all interfaces or a specific interface |
| show interface port-channel <#> | show interface port-channel <#> | Displays statistics for a specific port-channel |
| - | - | - |
| show port-channel capacity | - | Displays port-channel resources (total, used, free) |
| show port-channel compatibility-parameters | - | Displays the compatibility-parameters (IE: speed, duplex, etc) |
| show port-channel database | - | Displays the aggregation state for one or more port-channels |
| show port-channel load-balance | show etherchannel load-balance | Displays the load-balancing algorithm (hash) configured |
| show port-channel summary | show etherchannel summary | Displays a summarized list of all port-channels |
| show port-channel traffic | - | Displays the load per link in a port-channel (Based in interface counters) |
| show port-channel usage | - | Displays the range of used and unused port-channel numbers |
| - | - | - |
| show lacp counters | show lacp counters | Displays the LaCP PDU and error counters |
| show lacp interface | - | Displays detailed LaCP information per interface |
| show lacp neighbors | show lacp neighbors | Displays detailed LaCP information per neighbor |
| show lacp port-channel | show lacp <port-channel-#> | Displays the port-channel LaCP configuration |
| show lacp system-identifier | show lacp sys-id | Displays the LaCP system ID (Priority / MAC address) |
