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First active switch from the stack provides the Bridge ID of the stack (MAC address of the stack). When the switch which became first active on the stack is removed the stack will keep the Bridge ID. If the whole stack is reloaded when the first active switch is faulty/removed Bridge ID election will occur again and Bridge ID of the stack will change, If port mapping is integrated to external tools it can be affected
If the stack is reloaded when the first active switch is faulty/removed Bridge ID election will occur again.
To avoid the that the new master election changes the Bridge ID we can use: 1. stack-mac persistent timer 0 (This command keeps the mac of the first active switch on the stack, we can decide which switch will be the first active switch by modifying the priority of the switches) 2. Stack switch priority (If we modify the priority of the switches, we can set the higher priority to the switch we want to become Active after reloads and upgrades) If we use these tools, we will be able to keep the Bridge ID of the stack on the below scenarios: 1. If the Active switch which provided the Bridge ID is reloaded 2. If the whole stack is reloaded 3. If the active switch fails 4. If we choose a different switch as active This means that in these 4 scenarios the Bridge ID will not change no matter which of them happen The scenario where the Bridge ID of the stack will change even if configure the options to keep it will be: 1. If the first active switch is faulty and we remove it from the stack and then reload all the switches from the stack at the same time
TARTRE#sh version Cisco IOS XE Software, Version 17.06.03 Cisco IOS Software [Bengaluru], Catalyst L3 Switch Software (CAT9K_IOSXE), Version 17.6.3, RELEASE SOFTWARE (fc4) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2022 by Cisco Systems, Inc. Compiled Wed 30-Mar-22 23:09 by mcpre Cisco IOS-XE software, Copyright (c) 2005-2022 by cisco Systems, Inc. All rights reserved. Certain components of Cisco IOS-XE software are licensed under the GNU General Public License ("GPL") Version 2.0. The software code licensed under GPL Version 2.0 is free software that comes with ABSOLUTELY NO WARRANTY. You can redistribute and/or modify such GPL code under the terms of GPL Version 2.0. For more details, see the documentation or "License Notice" file accompanying the IOS-XE software, or the applicable URL provided on the flyer accompanying the IOS-XE software. ROM: IOS-XE ROMMON BOOTLDR: System Bootstrap, Version 17.12.1r, RELEASE SOFTWARE (P) TARTRE uptime is 17 hours, 43 minutes Uptime for this control processor is 17 hours, 47 minutes System returned to ROM by Reload Command System image file is "flash:/cat9k_iosxe.17.06.03.SPA.bin" Last reload reason: Reload Command If you require further assistance please contact us by sending email to export@cisco.com. Technology Package License Information: ------------------------------------------------------------------------------ Technology-package Technology-package Current Type Next reboot ------------------------------------------------------------------------------ network-advantage Smart License network-advantage dna-advantage Subscription Smart License dna-advantage AIR License Level: AIR DNA Advantage Next reload AIR license Level: AIR DNA Advantage Smart Licensing Status: Registration Not Applicable/Not Applicable cisco C9300L-24UXG-2Q (X86) processor with 1317232K/6147K bytes of memory. Processor board ID FOC2403L7P9 2 Virtual Ethernet interfaces 48 Gigabit Ethernet interfaces 48 Ten Gigabit Ethernet interfaces 6 Forty Gigabit Ethernet interfaces 2048K bytes of non-volatile configuration memory. 8388608K bytes of physical memory. 1638400K bytes of Crash Files at crashinfo:. 11264000K bytes of Flash at flash:. 1638400K bytes of Crash Files at crashinfo-3:. 11264000K bytes of Flash at flash-3:. 1638400K bytes of Crash Files at crashinfo-2:. 11264000K bytes of Flash at flash-2:. Base Ethernet MAC Address : 4c:e1:76:23:f4:00 Motherboard Assembly Number : 73-19172-06 Motherboard Serial Number : FOC23501H64 Model Revision Number : A0 Motherboard Revision Number : A0 Model Number : C9300L-24UXG-2Q System Serial Number : FOC2403L7P9 CLEI Code Number : Switch Ports Model SW Version SW Image Mode ------ ----- ----- ---------- ---------- ---- * 1 35 C9300L-24UXG-2Q 17.06.03 CAT9K_IOSXE BUNDLE 2 35 C9300L-24UXG-2Q 17.06.03 CAT9K_IOSXE BUNDLE 3 35 C9300L-24UXG-2Q 17.06.03 CAT9K_IOSXE BUNDLE TARTRE#show switch ? All of them have the same priority Switch/Stack Mac Address : 4ce1.7623.f400 - Local Mac Address Mac persistency wait time: Indefinite H/W Current Switch# Role Mac Address Priority Version State ------------------------------------------------------------------------------------- *1 Active 4ce1.7623.f400 1 V01 Ready 2 Member c4b2.39d9.be80 1 V01 Ready 3 Standby c4b2.397b.5c80 1 V01 Ready The command is not applied yet: TARTRE#show run | i persis TARTRE#show run all | i persis no logging persistent no ip access-list persistent no transport type persistent telnet input TARTRE# Now we perform a switchover TARTRE#redundancy force-switchover System configuration has been modified. Save? [yes/no]: y Building configuration... [OK]Proceed with switchover to standby RP? [confirm] Manual Swact = enabled Chassis 1 reloading, reason - Non participant detected Without applying the command the Bridge ID is still the mac of first active switch after switch 3 taking the active role TARTRE#sh switch Switch/Stack Mac Address : 4ce1.7623.f400 - Local Mac Address Mac persistency wait time: Indefinite H/W Current Switch# Role Mac Address Priority Version State ------------------------------------------------------------------------------------- 1 Member 4ce1.7623.f400 1 V01 Initializing 2 Standby c4b2.39d9.be80 1 V01 Ready *3 Active c4b2.397b.5c80 1 V01 Ready When we apply the command an advertisement is displayed indicating that if the active switch mac is else where in the network traffic will be blackholed TARTRE(config)#stack-mac persistent timer 0 WARNING: Stack MAC persistency timer value of 0 means that, after a WARNING: active switchover, the current stack-mac will continue WARNING: to be used indefinitely. WARNING: The Network Administrators must make sure that the old WARNING: stack-mac does not appear elsewhere in this network WARNING: domain. If it does, user traffic may be blackholed. Saving current config TARTRE#wr Building configuration... [OK] TARTRE#sh run | in pers stack-mac persistent timer 0 Then we removed first active switch mac ?donor? from the stack TARTRE#sh switch Switch/Stack Mac Address : 4ce1.7623.f400 - Foreign Mac Address Mac persistency wait time: Indefinite H/W Current Switch# Role Mac Address Priority Version State ------------------------------------------------------------------------------------- 1 Member 0000.0000.0000 0 V01 Removed 2 Standby c4b2.39d9.be80 1 V01 Ready *3 Active c4b2.397b.5c80 1 V01 Ready Uptime of the switch is 5 hours which means that it already have a reload switch 3 is the new Active TARTRE uptime is 5 hours, 54 minutes Uptime for this control processor is 6 hours, 2 minutes System returned to ROM by SSO Switchover System image file is "flash:/cat9k_iosxe.17.06.03.SPA.bin" Last reload reason: PowerOn We proceed to reload the stack again TARTRE#reload System configuration has been modified. Save? [yes/no]: y Building configuration... [OK]Reload command is being issued on Active unit, this will reload the whole stack Proceed with reload? [confirm] TARTRE>sh sw Switch/Stack Mac Address : c4b2.397b.5c80 - Local Mac Address Mac persistency wait time: Indefinite H/W Current Switch# Role Mac Address Priority Version State ------------------------------------------------------------------------------------- 1 Member 0000.0000.0000 0 Provisioned 2 Standby c4b2.39d9.be80 1 V01 HA sync in progress *3 Active c4b2.397b.5c80 1 V01 Ready The mac (Bridge ID) changes if the stack is reloaded and first active switch is removed/faulty