cisco-ios-patternslisted

# Cisco IOS Patterns Use this skill when reviewing Cisco IOS or IOS-XE snippets, building a change-window checklist, or explaining how to collect evidence from a router or switch without making the incident worse. ## When to Use - Reviewing IOS or IOS-XE configuration before a planned change. - Choosing read-only `show` commands for troubleshooting. - Checking ACL wildcard masks and interface direction. - Explaining global, interface, routing process, and line configuration modes. - Verifying that a change landed in running config and was saved intentionally. ## Operating Rules Treat IOS examples as patterns, not paste-ready production changes. Confirm the platform, interface names, current config, rollback path, and out-of-band access before making changes on a real device. Prefer this workflow: 1. Capture current state with read-only commands. 2. Review the exact candidate config. 3. Confirm management access cannot be locked out. 4. Apply the smallest change in a maintenance window. 5. Re-read state, compare to the baseline, then save only after validation. ## Mode Reference ```text Router> enable Router# show running-config Router# configure terminal Router(config)# interface GigabitEthernet0/1 Router(config-if)# description UPLINK-TO-CORE Router(config-if)# no shutdown Router(config-if)# exit Router(config)# end Router# show running-config interface GigabitEthernet0/1 ``` `running-config` is active memory. `startup-config` is what survives reload. Do not save a