TFTP Won't Connect

[admin_2]

Hello All,

I've been trying for a couple of days now to get TFTP downloads to work on my 2900XL router (IOS v. 12.0(5.2), XU). I have a working TFTP server -- I have verified that it functions by having a different machine download the file in question. However, whenever I attempt to download a straight text file to flash from this server, TFTP on my router times out.

What's particularly interesting is tcpdump output:

12:46:08.404207 arp reply 192.168.1.254 is-at 0:d0:97:68:b5:0

12:46:08.405413 192.168.1.254.5911 > 192.168.1.2.69: [udp sum ok] 18 RRQ "vlan2.txt" (ttl 255, id 0, len 46)

12:46:12.407065 192.168.1.254.5911 > 192.168.1.2.69: [udp sum ok] 18 RRQ "vlan2.txt" (ttl 255, id 1, len 46)

12:46:17.408087 192.168.1.254.5911 > 192.168.1.2.69: [udp sum ok] 18 RRQ "vlan2.txt" (ttl 255, id 2, len 46)

The above 3-packet request sequence is sent 3 times -- on 3 different attempts to get the file -- before this output follows:

12:47:23.450543 192.168.1.2.33670 > 192.168.1.254.5911: udp 392 (ttl 64, id 64980, len 420)

12:47:23.450707 192.168.1.2.33668 > 192.168.1.254.5911: udp 392 (ttl 64, id 64981, len 420)

12:47:23.476483 192.168.1.254 > 192.168.1.2: icmp: 192.168.1.254 udp port 5911 unreachable [tos 0xc0] (ttl 255, id 11375, len 56)

12:47:27.450510 192.168.1.2.33674 > 192.168.1.254.5911: udp 392 (ttl 64, id 64989, len 420)

12:47:27.450648 192.168.1.2.33672 > 192.168.1.254.5911: udp 392 (ttl 64, id 64990, len 420)

12:47:27.473301 192.168.1.254 > 192.168.1.2: icmp: 192.168.1.254 udp port 5911 unreachable [tos 0xc0] (ttl 255, id 11376, len 56)

12:47:28.460177 192.168.1.2.33668 > 192.168.1.254.5911: udp 392 (ttl 64, id 64994, len 420)

12:47:28.469833 192.168.1.254 > 192.168.1.2: icmp: 192.168.1.254 udp port 5911 unreachable [tos 0xc0] (ttl 255, id 11377, len 56)

It looks like my router simply won't take UDP packets inbound. Now, I can't verify precisely that there is no kind of access control or firewalling going on on this router, since I inherited it from someone else here at work, but at a glance, it appears to be wide open, as show access-list is completely blank.

Does anyone have any idea why this router can't receive UDP packets?

Thanks,

Alex Kirk

[zahmed]

Is the TFTP successful in the other direction (from 2900XL to the TFTP server)?

~Zulfi

[Richard Burts]

I assume that you are doing a copy tftp flash on the router to initiate the tftp transfer. The cisco router gets enough information to initiiate the transfer (address of server and name of file) and verifies access to the server by requesting a transfer of the specified file from the server. This verifies that things will work (that there is IP connectivity to the remoet address, that the remote box is running tftp server software, that the file exists, and that your permissions are sufficient to get the file).

Once the router has determined that the transfer can be done, it terminates the transfer (the port unreachable messages you are seeing) and proceeds to check some other things - is there enough room in flash, does flash need to be erased, etc). Once it has the rest of the information that it needs it initiates the transfer again.

It would be very helpful to know exactly what happens in your session to the router when you attempt the tftp (what prompts does the router present, what responses do you give). This might help to determine why the transfer is not succeeding.

[deilert]

make sure the permissions on your file are set to rw