shirwa’s blog

November 15, 2007

Backing up Cisco configuration file using tftpd in Linux

Filed under: GNU/Linux — Tags: , , , — shirwa @ 8:46 am

TFTP (Trivial File Transfer Protocol), a simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP)and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and to backup routers configurations files.

Some details of TFTP:

  • It uses UDP port 69 as its transport protocol (unlike FTP which uses TCP port 21).
  • It cannot list directory contents.
  • It has no authentication or encryption mechanisms.
  • It is used to read files from, or write files to, a remote server.
  • It supports three different transfer modes, “netascii”, “octet” and “mail”, with the first two corresponding to the “ASCII” and “image” (binary) modes of the FTP protocol; the third is now obsolete and is rarely used.
  • The original protocol has a file size limit of 32 MB, although this was extended when RFC 2347 introduced option negotiation, which was used in RFC 2348 to introduce block-size negotiation in 1998 (allowing a maximum of 4 GB and potentially higher throughput). If the server and client support block number wraparound, file size is essentially unlimited.
  • Since TFTP utilizes UDP, it has to supply its own transport and session support. Each file transferred via TFTP constitutes an independent exchange. That transfer is performed in lock-step, with only one packet (either a block of data, or an ‘acknowledgement’) ever in flight on the network at any time. Due to this lack of windowing, TFTP provides low throughput over high latency links.
  • Due to the lack of security, it is dangerous over the open Internet. Thus, TFTP is generally only used on private, local networks.

To install it in Debian or ubuntu:

#apt-get install tftpd tftp

edit /etc/xinetd.d/tftp file, if file doesnt exist create one.

service tftp

{

disable = no

socket_type = dgram

protocol = udp

wait = yes

user = root

server = /usr/sbin/in.tftpd

server_args = -s /tftpboot

per_source = 11

cps = 100 2

flags = IPv4

}

Create a directory called tftpboot in root

#mkdir /tftpboot

Change mode of the directory

#chmod 777 tftpboot

Restart xnetd
#/etc/inid.d/xinetd restart

Now test your connections

#tftp 192.168.10.10

Telnet to your cisco router and start backing up your configuration files.

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3 Comments »

  1. Restart xnetd
    #/etc/inid.d/xinetd restrat

    Should be

    Restart xinetd
    # ./etc/init.d/xinetd restart

    Comment by Christopher — November 20, 2007 @ 4:41 am

  2. Great documentation,. 🙂

    Comment by Christopher — November 20, 2007 @ 4:41 am

  3. Christopher thanks, it was typo, i should double check what i post next time.

    Comment by shirwa — November 20, 2007 @ 10:10 am


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