How to set up Link Dependency on a Dell EMC Networking N-Series Switch

This article explains how Actions (UP/Down) influence Link dependency in Dell EMC Networking N-Series switch.

Link dependency allows us to influence the link status of a group of interface based on the link status of another group of interfaces. The groups can include portchannels and individual ports.  This feature can be used to avoid redundant links to avoid loop.

Overview

1.  Actions
2.  Behavior of Link dependency group based on action
3.  Points to be noted before configuration
4.  Command Syntax
5.  Sample Configuration
5.  Example of how to verify the status of the  link dependency when action is up
6.  Example of how to verify the status of the  link dependency when action is down
 

Actions

There are two possible actions in response to a link status change of depended-on interface.

Up : The member port inverts the link status of the depended-on interface.
Example: Consider port Gi1/0/2 is link depended-on Gi1/0/1 and the action is configured to Up.
If port Gi1/0/1 goes down, Gi1/0/2 comes up.
If port Gi1/0/1 goes up, Gi1/0/2 comes down. 

Down : The member port mirrors the link status of the depended-on interface.
Example: Consider port Gi1/0/2 is link depended-on Gi1/0/1 and the action is configured to Down.
If port Gi1/0/1 goes up, Gi1/0/2 comes up.
If port Gi1/0/1 goes down, Gi1/0/2 comes down. 
 

Behavior of Link dependency group based on action

We can configure a group of interfaces/port-channel as member ports  and depended-on interfaces.

Action: Up
Only if, all the depended-on interfaces are down, the member ports of group will come up.

Action: Down
If at least one of the depended-on interface is up, the member ports of group will stay up
 

Points to be noted before configuration

An interface can only be a member of a single dependency group.

Adding an interface to a dependency list brings the interface down until the depends-on command is entered. The link status will then follow the interface specified in the depends-on command. To avoid bringing down interfaces, enter the depends-on and action command prior to entering the add command.

Command Syntax

Sample configuration

Action: Up
console#configure
console(config)#link-dependency group 1
console(config-linkDep-group-1)#action up
console(config-linkDep-group-1)#depends-on gigabitethernet 1/0/1
console(config-linkDep-group-1)#add gigabitethernet 1/0/2

Action: Down
console#configure
console(config)#link-dependency group 1
console(config-linkDep-group-1)#action down
console(config-linkDep-group-1)#depends-on gigabitethernet 1/0/1
console(config-linkDep-group-1)#add gigabitethernet 1/0/2
 

Example of how to verify the status of the  link dependency when action is up
 

a. Consider port Gi1/0/2 is link depended-on Gi1/0/1 and Gi1/0/1 is up

console#show interfaces status
Port      Description     Duplex Speed   Neg  Link   Flow  M  VLAN
                                              State  Ctrl
--------- --------------- ------ ------- ---- ------ ----- -- -------------------
Gi1/0/1                   Full   1000    Auto Up     On    A  1
Gi1/0/2                   N/A    Unknown Auto Down   Off   A  1

console#show link-dependency
GroupId  Member Ports                        Ports Depended On       Link Action  Group State
-------  ----------------------------------  --------------------    -----------  -----------
  1      Gi1/0/2                             Gi1/0/1                 Link Up      Down


b. Consider port Gi1/0/2 is link depended-on Gi1/0/1 and Gi1/0/1 is down

console#show interfaces status

Port      Description     Duplex Speed   Neg  Link   Flow  M  VLAN
                                              State  Ctrl
--------- --------------- ------ ------- ---- ------ ----- -- -------------------
Gi1/0/1                   N/A    Unknown Auto Down   Off   A  1
Gi1/0/2                   Full   1000        Auto   Up     On    A  1


console#show link-dependency
GroupId  Member Ports    Ports Depended On   Link Action  Group State
-------  -------------------------  --------------------           -----------     -----------
  1      Gi1/0/2                             Gi1/0/1                 Link Up      Up

 

Example of how to verify the status of the  link dependency when action is down

a. Consider port Gi1/0/2 is link depended-on Gi1/0/1 and Gi1/0/1 is up

console#show interfaces status
Port      Description     Duplex Speed   Neg  Link   Flow  M  VLAN
                                              State  Ctrl
--------- --------------- ------ ------- ---- ------ ----- -- -------------------
Gi1/0/1                   Full   1000    Auto Up     On    A  1
Gi1/0/2                   Full   1000    Auto Up     On    A  1

console#show link-dependency
GroupId  Member Ports    Ports Depended On  Link Action  Group State
-------  ------------------------  --------------------          -----------        -----------
  1      Gi1/0/2                             Gi1/0/1             Link Down     Up

b. Consider port Gi1/0/2 is link depended-on Gi1/0/1 and Gi1/0/1 is down

console#show interfaces status
Port      Description     Duplex Speed   Neg  Link   Flow  M  VLAN
                                              State  Ctrl
--------- --------------- ------ ------- ---- ------ ----- -- -------------------
Gi1/0/1                   N/A    Unknown Auto Down   Off   A  1
Gi1/0/2                   N/A    Unknown Auto Down   Off   A  1


console#show link-dependency
GroupId  Member Ports           Ports Depended On   Link Action  Group State
-------  ----------------------------------  --------------------         -----------  -----------
  1      Gi1/0/2                             Gi1/0/1                       Link Down    Down