I believe the zeros represent lost packets.

[edit]

PS:

Believe tftp will resend lost packets.

To check if the image is not corrupted or not :

do "verify flash:" if checksum is OK its verified .

Peter,

This should explain it:

http://www.cisco.com/en/US/docs/ios/12_3/configfun/command/reference/cfr_1g02.html#wp1030397

It means packets were received out of order, but it can still succeed. This can be seen in a network with load-balanced links.

Phil Leinster

CCIE #21467

Used my desktop Win10, tftpd64. I deleted the current IOS on 3560, then did a tftp and got !OO!OO!OO!OO!OO!OO!OOO!OO!... [timed out].

I tried changing the tftpd64 settings, timeout 6 & retransmit 10 (like others suggested, it didn't help).

3560 doesn't have the command "ip tftp block-size xxxx"

The solution for me was to use another tftp server and program, I used my Solarwinds server with Solarwinds tftp and it was all good (but it took a long time). I know it is best to do it on a local pc, but I don't have that option, I'm doing the tftp over a WAN link.

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WS-C3560V2-48PS#delete /recursive /force flash:c3560-ipbasek9-mz.122-55.SE12.bin

WS-C3560V2-48PS#dir
Directory of flash:/

2 -rwx 796 Aug 30 2017 15:17:17 -05:00 vlan.dat
3 -rwx 5511 Sep 21 2020 17:32:19 -05:00 private-config.text
5 -rwx 4120 Sep 21 2020 17:32:19 -05:00 multiple-fs
6 drwx 512 May 1 1993 13:39:31 -05:00 crashinfo_ext
8 -rwx 64627 Sep 21 2020 17:32:18 -05:00 config.text

WS-C3560V2-48PS#copy tftp://10.10.10.247/c3560-ipbasek9-mz.150-2.SE11.bin flash:c3560-ipbasek9-mz.150-2.SE11.bin
Destination filename [c3560-ipbasek9-mz.150-2.SE11.bin]?
Accessing tftp://10.10.15.247/c3560-ipbasek9-mz.150-2.SE11.bin...
Loading c3560-ipbasek9-mz.150-2.SE11.bin from 10.10.15.247 (via Vlan10): !OO!OO!OO!OO!OO!OO!OOO!OO!... [timed out]

WS-C3560V2-48PS#copy tftp://10.10.10.100/c3560-ipbasek9-mz.150-2.SE11.bin flash:c3560-ipbasek9-mz.150-2.SE11.bin
Destination filename [c3560-ipbasek9-mz.150-2.SE11.bin]?
Accessing tftp://10.10.18.100/c3560-ipbasek9-mz.150-2.SE11.bin...
Loading c3560-ipbasek9-mz.150-2.SE11.bin from 10.10.18.100 (via Vlan10): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!O!!!!!!!!!!
[OK - 16664448 bytes]
16664448 bytes copied in 1200.217 secs (13885 bytes/sec)

WS-C3560V2-48PS#verify /md5 flash:c3560-ipbasek9-mz.150-2.SE11.bin
.........................................................................................................................................................................Done!
verify /md5 (flash:c3560-ipbasek9-mz.150-2.SE11.bin) = b81d9bfd47be75d966d122af60003fef