With the addition of USB ports on the newer Cisco routers, it has made it much easier to load IOS upgrades in staging areas - where equipment is being configured prior to being installed.  In the past, having a PC either directly connected to the staging equipment or plugged into the same network as the device was the way to upgrade the IOS using tftp.  Sometimes that staging area is a cubicle and causes a hassle if there isn’t a dedicated PC available for upgrades, because it means unhooking your primary pc from the network (which is the same pc needed to download all the software upgrades from cisco.com).

I have one USB thumb drive that is used strictly for Cisco gear.  First I started with a 256Mb freebie that come from a vendor and inserted it into a 2811 router that was up and running.  The flash was then formatted from the router to insure there would be no issues with the filesystem when using it in future Cisco devices.

Router#format usbflash1:
Format operation may take a while. Continue? [confirm]
Format operation will destroy all data in "usbflash1:".  Continue? [confirm]
Format: Drive communication & 1st Sector Write OK...

Format: All system sectors written. OK...

Format: Total data sectors in formatted partition: 511435
Format: Total data bytes in formatted partition: 261854720
Format: Operation completed successfully.

Format of usbflash1 complete
Router#

Next the thumb drive was inserted into the pc and the IOS image copied to it.  In this scenario, a Catalyst 3560 switch is being upgraded which is connected directly to a 2811 router that will serve as the tftp server.  

The router’s FastEthernet0/0 interface is connected to the switch, which is in the same vlan as the management interface (Vlan1) of the switch.

Router#show ip int brief | exc unassigned
Interface               IP-Address      OK? Method  Status     Protocol
FastEthernet0/0         10.1.2.1        YES manual  up         up
Serial0/0/0             192.168.40.214  YES manual  down       down
Loopback1               10.254.1.18     YES manual  up         up
Router#

Connectivity to the access switch is then verified using ping:

Router#ping 10.1.2.5

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.2.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
Router#

The thumb drive is then put back in the router and the contents of the usb drive is verified.

Router#dir usbflash1:
Directory of usbflash1:/

    1  -rw-     8811199  Sep 04 2008 10:18:38 +00:00  c3560-ipbasek9-mz.122-46.SE.bin

261853184 bytes total (252272640 bytes free)
Router#

Router(config)#tftp-server usbflash1:c3560-ipbasek9-mz.122-46.SE.bin

From the switch console, we should now be able to perform an IOS upgrade using the connected router as the tftp source:

Switch#copy tftp://10.1.2.1/c3560-ipbasek9-mz.122-46.SE.bin flash:
Destination filename [c3560-ipbasek9-mz.122-46.SE.bin]?
Accessing tftp://10.1.2.1/c3560-ipbasek9-mz.122-46.SE.bin...
Loading c3560-ipbasek9-mz.122-46.SE.bin from 10.1.2.1 (via Vlan1): !!!!!!!!!!!!!!!<truncated>
[OK - 8811199 bytes]
 

8811199 bytes copied in 151.591 secs (58125 bytes/sec)
Switch#

Using the router as a tftp server along with the removable storage proves to be a convinient method for upgrading other IOS devices in situations where a spare pc is not readily available. Don’t forget to clean up the router after your finished by removing the tftp-server command.