There are two scenarios in which the stack might be broken. First, one of the two units, base
or non-base unit, has failed due to power interruption or other hardware problem. Second, at
least one of the stack cables connecting the two units has failed.
In the case of a one-unit failure, the remaining unit keeps the previous stack IP settings. The
remaining unit issues a gratuitous ARP packet after entering Stack Forced Mode in order for
other devices on the network to update their ARP cache.
After entering Stack Forced Mode, the device sends an SNMP trap informing the administrator
that the switch has entered this mode. The trap information contains the switch IP and MAC
addresses, which allows you to know if two devices are using the same IP address. The format
for this trap is
Trap: Device is functioning in Forced Stack Mode – MAC: yy:yy:yy:yy:yy:yy
. The
yy:yy:yy:yy:yy:yy
represents the device MAC address.
A device functions in Stack Forced Mode either until the unit is rebooted or until the unit joins
a stack.
The Stack Forced Mode feature is configurable using ACLI. The commands in Global
Configuration Mode are as follows:
• stack forced-mode enables Stack Forced Mode
• no stack forced-mode disables Stack Forced Mode
• default stack forced-mode sets the Stack Forced Mode to the default setting. The
default is disabled.
While in PrivExec mode, you can use the show stack forced-mode command. Depending
on the configuration and if the device is currently functioning in Stack Forced Mode, the output
is one of three options:
1. If the Stack Forced Mode is not configured on the device, the output is:
Forced-Stack Mode: Disabled
Device is not currently running in forced stack mode.
2. If the Stack Forced Mode is configured on the device, but inactive, the output is:
Forced-Stack Mode: Enabled
Device is not currently running in forced stack mode.
3. If the Stack Forced Mode is configured on the device, and the device is currently
running in Stack Forced Mode, the output is:
Forced-Stack Mode: Enabled
Device is currently running in forced stack mode.
Troubleshooting tools
30 Troubleshooting Avaya ERS 4000 Series April 2014
Comments? infodev@avaya.com
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