[问题描述]
客户现场交换机异常，其实与我没有什么关系。交换机是他们自己负责的，我们只有系统而已。不过他们的交换机供应商只是让他们提供序列号协助保修，至于序列号在什么位置如何获取则没有告知他们。（客户已经用一台傻瓜TP-LINK交换机顶替让业务临时对应的）

[问题分析]
虽然不在我职责范围，不过毕竟与客户非常熟悉。我还是以私人角度告诉他如何获取序列号。可以有如下方法：
1.物理目视法；
2.登录系统查看法；

[问题步骤]
1.物理目视法；
思科设备交换机、路由、防火墙都会在设备机身上有明确的标签记录SN序列号。

2.登录系统查看法；
在设备CLI界面输入”show version”，在显示的信息里面查看序列号。针对不同的设备型号或IOS，显示序列号的方式不太一样，对于大部分交换机系列的设备，会显示Processor board ID：LLLYYWWXXXX，对于一些其他设备可能会显示System serial number：LLLYYWWXXXX，或者Serial Number: LLLYYWWXXXX。

特别注意的是交换机系列，因为交换机内部有不同的板卡，每个板卡会有不同的设备序列号，在”show version”显示的结果中，会出现很多类似序列号的字符和数字，您只需要关注Processor board ID后面接的序列号即可。

思科AP交换机输出结果，序列号关键字[Processor board ID]：

Cisco IOS Software, C1240 Software (C1240-K9W8-M), Version 12.4(23c)JA, RELEASE
SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2010 by Cisco Systems, Inc.
Compiled Tue 01-Jun-10 13:18 by prod_rel_team

ROM: Bootstrap program is C1240 boot loader
BOOTLDR: C1240 Boot Loader (C1240-BOOT-M) Version 12.4(13d)JA, RELEASE SOFTWARE
(fc2)

1H-2F-AP-L2-2 uptime is 5 hours, 23 minutes
System returned to ROM by power-on
System image file is "flash:/c1240-k9w8-mx.124-23c.JA/c1240-k9w8-mx.124-23c.JA"


This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

cisco AIR-LAP1242AG-C-K9   (PowerPCElvis) processor (revision A0) with 25590K/71
68K bytes of memory.
Processor board ID FGL1518U0CM
PowerPCElvis CPU at 262Mhz, revision number 0x0950
Last reset from power-on
LWAPP image version 7.0.98.0
1 FastEthernet interface
2 802.11 Radio(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: E8:B7:48:4C:F4:EA
Part Number                          : 73-10256-07
PCA Assembly Number                  : 800-26918-06
PCA Revision Number                  : A0
PCB Serial Number                    : FOC15153ACZ
Top Assembly Part Number             : 800-29152-03
Top Assembly Serial Number           : FGL1518U0CM
Top Revision Number                  : A0
Product/Model Number                 : AIR-LAP1242AG-C-K9

Configuration register is 0xF

[问题参考]
1.序列号构成说明，以此格式为例：LLLYYWWXXXX

Cisco S/N format is LLLYYWWXXXX.
LLL = Location code (i.e. FOC = FoxConn China)
YY = Year code (08 = 2004…09=2005…etc…)
WW = Week code (weeks 01 to 52)
XXXX = Base-34 Alpha Numeric Unique identifier (Includes 0 to 9 & entire alphabet except I & O).


Location codes:
CTH — Celestica – Thailand
FOC — Foxconn – Shenzhen, China
JAB — Jabil – Florida
JPE — Jabil – Malaysia
JSH — Jabil – Shanghai , China
TAU — Solectron – Texas
PEN — Solectron – Malaysia

Year codes:
11 = 2007
12 = 2008
13 = 2009
14 = 2010
15 = 2011
16 = 2012
17 = 2013
18 = 2014
19 = 2015
20 = 2016
21=  2017
22 = 2018
23 = 2019
24 = 2020
25 = 2021

Weed Codes:
1-5 : January                  
15-18 : April                        
28-31 : July                          
41-44 : October
6-9 : February                
19-22 : May                         
32-35 : August                   
45-48 : November
10-14 : March                 
23-27 : June                        
36-40 : September           
49-52 : December