What is the stack management subnet?
Internal communication between the Stack members is carried out using IP packets sent over the stacking links. This stack management traffic is tagged with a specific ID and uses IP addresses in a specified subnet.By default, the VLAN and subnet used are:
- VLAN 4094
- Subnet 192.168.255.0/27
It is important that the settings for management subnet and management VLAN are the same for all the Switches in a Stack. If a Switch is added to a Stack, and its setting for management VLAN and/or management subnet differ from those on the other Stack members, the new Switch will not be able to join the stack and a log message like the following will be created:
06:51:41 awplus-vcs VCS(1066) : Member 2 (0009.41fd.dd0b) cannot join stack – incompatible VCS management subnet
Why can’t an address overlapping with the stack management subnet be used?
Since the subnet 192.168.255.0/27 by default is reserved for stack management, an IP space containing this range such as 192.168.0.1/16 can result in potential address conflict with stack member.
Attempt to configure this space on an interface will result in the following error message:
awplus (config-if)# ip address 192.168.0.1/16
% Warning: IP address 192.168.0.1/16 overlaps with stack management subnet
% IP connectivity with any host within 192.168.255.0/27 is not supported
In addition, attempt of configuring address within the Stack management range will result in another error message:
awplus (config-if)# ip address 192.168.255.1/24
% IP address 192.168.255.1/24 not added as it interferes with the stack management network..
How to change the default Stack management subnet to allow using designated IP space?
If an IP address that overlaps with the default Stack management subnet needs to be used, please follow these commands below to modify the default value to a different IP space:
awplus>enable
awplus#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
awplus(config)#stack management subnet 172.21.255.64
% Save the config and restart the system for this change to take effect.
awplus(config)#end
awplus#copy running-config startup-config
Once the configuration is saved, restart the Switch for the change to take effect.Note: The last octet of the Stack management subnet needs to be multiple of 32 or there will be an error:
% The ip address 172.21.255.65 can not be used as the stacking management VLAN subnet address
There is no requirement for the other octets other than it cannot overlap with an existing IP space configured on the switch.
Conclusion
By default, the 192.168.255.0/27 network is reserved in stackable Allied Ware+ devices, this network can be changed with steps provided in this article to avoid conflict with designated IP address that overlaps with it.