本檔案將說明為什麼系統訊息「System returned to ROM by abort」或「System returned to ROM by trace trap」會出現在show version指令的輸出中。本文檔還說明啟動並運行的路由器可能返回ROMmon模式的原因。
本文件沒有特定需求。
本文件所述內容不限於特定軟體和硬體版本。
本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路正在作用，請確保您已瞭解任何指令可能造成的影響。
如需文件慣例的詳細資訊，請參閱思科技術提示慣例。
除了硬體和軟體版本等資訊外，show version命令的輸出還顯示有關如何重新啟動系統的資訊。例如，透過reload命令重新啟動的路由器會顯示「System returned to ROM by reload」消息，而重新通電以重新啟動的路由器會顯示「System returned to ROM by power-on」消息。有時，可能會出現以下消息：
Router uptime is 1 minute
System returned to ROM by abort at PC 0x8032A6EC
System image file is "flash:C2600-i-mz.122-10b.bin"
或
Router uptime is 2 minutes
System returned to ROM by trace trap at PC 0x32C2064
System image file is "flash:/c2500-js-l.122-10b"
出現「abort」或「trace trap」訊息表示組態暫存器可能設定為可在正常操作時啟用break鍵的值。位元編號08 (以十六進位表示： 0x0100)，如果設定，會停用Break金鑰（也就是出廠預設值）。如果將其重設為0(可明確表示在0x2002中，或隱含表示在0x2中，相當於0x0002)，Break金鑰將會啟用。當啟用了Break鍵時，Break序列會使路由器進入ROMmon模式，即使在路由器已啟動並正常運行之後也是如此。即使控制檯未故意傳送中斷訊號，某些行為不當或重新載入的終端也可能不小心向路由器傳送與中斷序列類似的訊號。
有關不同配置暫存器值的詳細資訊，請參閱配置暫存器位的含義。
在show version命令的結尾，您可以檢查配置暫存器的值：
Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-JS-L), Version 12.2(10b), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2002 by cisco Systems, Inc.
Compiled Fri 12-Jul-02 02:13 by pwade
Image text-base: 0x0307AA24, data-base: 0x00001000
ROM: System Bootstrap, Version 11.0(10c), SOFTWARE
BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1)
R1 uptime is 9 minutes
System returned to ROM by trace trap at PC 0x32C2064
System image file is "flash:/c2500-js-l.122-10b"
cisco 2500 (68030) processor (revision F) with 16384K/2048K bytes of memory.
Processor board ID 04796554, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
Basic Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read ONLY)
Configuration register is 0x2002
為防止路由器意外返回ROMmon模式，請將配置暫存器更改為停用中斷鍵的值。為此，請將配置暫存器的第八位更改為1（最常用的值為0x2102）。
Router>enable
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#config-register 0x2102
Router(config)#^Z
00:20:13: %SYS-5-CONFIG_I: Configured from console by console
Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-JS-L), Version 12.2(10b), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2002 by cisco Systems, Inc.
Compiled Fri 12-Jul-02 02:13 by pwade
Image text-base: 0x0307AA24, data-base: 0x00001000
ROM: System Bootstrap, Version 11.0(10c), SOFTWARE
BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1)
Router uptime is 20 minutes
System returned to ROM by trace trap at PC 0x32C2064
System image file is "flash:/c2500-js-l.122-10b"
cisco 2500 (68030) processor (revision F) with 16384K/2048K bytes of memory.
Processor board ID 04796554, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
Basic Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read ONLY)
Configuration register is 0x2002 (will be 0x2102 at next reload)
使用配置暫存器集的第八位，系統受到保護，防止出現中斷訊號，否則可能導致路由器進入ROMmon模式。新的配置暫存器設定僅在下次重新載入時生效。請確保在停用Break鍵之前為該路由器安排停機時間。
註：在路由器重新載入或通電（在引導序列期間）後的前60秒內始終啟用Break鍵，與配置暫存器中第8位的狀態無關。如果透過配置暫存器停用或啟用Break鍵，則路由器僅會在正常運行期間受到影響，而不會在引導序列期間受到影響。
意見