CISCO模拟器Dynamips目前还存在一个缺点，使用“show flash”命令找不到IOS文件，所以无法完成Dynamips模拟CISCO IOS备份实验，现在在一台CISCO 3500真机上做实验如下：
1，下载tftp服务器软件(很小，只有160kb);
2，打开tftp服务器，如下图所示：
3，连接CISCO 3500交换机并测试与tftp服务器的连通性(ip地址为192.168.1.102)：
User Access Verification
Password:
storm>en
Password:
storm#ping 192.168.1.102
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.102, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 3/4/6 ms
4，将IOS文件保存到tftp服务器：
storm#show flash
Directory of flash:/
2 -rwx 1803795 Mar 01 1993 00:29:16 c3500xl-c3h2s-mz.120-5.WC8.bin
3 drwx 704 Mar 01 1993 00:29:51 html
15 -rwx 108 Mar 01 1993 00:29:52 info
16 -rwx 108 Mar 01 1993 00:29:52 info.ver
18 -rwx 1967 Mar 01 1993 02:11:12 config.text
3612672 bytes total (691712 bytes free)
storm#copy flash:c3500xl-c3h2s-mz.120-5.WC8.bin tftp:
Address or name of remote host []? 192.168.1.102
Destination filename [c3500xl-c3h2s-mz.120-5.WC8.bin]?
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
1803795 bytes copied in 13.183 secs (138753 bytes/sec)
storm#
5，查看存放tftp服务器软件目录下是否已经有CISCO 3500的IOS存在：
操作成功。