When you boot up the router for the first time, the router looks for a default file name-the PID of the router. For example, the Cisco 1000 Series Integrated Services Routers look for a file named isr1100.cfg. The Cisco 1000 Series ISR looks for this file before finding the standard files-router-confg or the ciscortr.cfg.
The Cisco 1000 ISR looks for the isr1100.cfg file in the bootflash. If the file is not found in the bootflash, the router then looks for the standard files-router-confg and ciscortr.cfg. If none of the files are found, the router then checks for any inserted USB that may have stored these files in the same particular order.
If there is a configuration file with the PID as its name in an inserted USB, but one of the standard files are in bootflash, the system finds the standard file for use.
Use the show running-config command to view the initial configuration, as shown in the following example:
Router# show running-config Building configuration... Current configuration : 1749 bytes ! ! Last configuration change at 20:23:33 UTC Fri Nov 3 2017 ! version 16.6 service timestamps debug datetime msec service timestamps log datetime msec platform qfp utilization monitor load 80 no platform punt-keepalive disable-kernel-core ! hostname Router ! boot-start-marker boot-end-marker ! ! ! no aaa new-model ! ! ! ! ! ! ! ! ! ! ! subscriber templating ! ! multilink bundle-name authenticated ! ! ! crypto pki trustpoint TP-self-signed-4175586959 enrollment selfsigned subject-name cn=IOS-Self-Signed-Certificate-4175586959 revocation-check none rsakeypair TP-self-signed-4175586959 ! ! crypto pki certificate chain TP-self-signed-4175586959 ! ! license udi pid C1111-8PLTELA sn FGL212694ML ! diagnostic bootup level minimal spanning-tree extend system-id ! ! ! redundancy mode none ! controller Cellular 0/2/0 lte modem link-recovery disable ! ! vlan internal allocation policy ascending ! ! ! ! ! ! interface GigabitEthernet0/0/0 no ip address shutdown negotiation auto ! interface GigabitEthernet0/0/1 no ip address shutdown negotiation auto ! interface GigabitEthernet0/1/0 ! interface GigabitEthernet0/1/1 ! interface GigabitEthernet0/1/2 ! interface GigabitEthernet0/1/3 ! interface GigabitEthernet0/1/4 ! interface GigabitEthernet0/1/5 ! interface GigabitEthernet0/1/6 ! interface GigabitEthernet0/1/7 ! interface Cellular0/2/0 ip address negotiated ipv6 enable ! interface Cellular0/2/1 no ip address shutdown ! interface Vlan1 no ip address ! ip forward-protocol nd ip http server ip http authentication local ip http secure-server ! ! ! ! ! ! control-plane ! ! line con 0 transport input none stopbits 1 line vty 0 4 login ! wsma agent exec ! wsma agent config ! wsma agent filesys ! wsma agent notify ! ! end