Introduction
Trivial File Transfer Protocol or simply TFTP is a very simple protocol used to transfer files. Each nonterminal packet is acknowledged separately.
ip/tftp/
This menu contains all TFTP access rules. If in this menu are no rules, the TFTP server is not started when RouterOS boots. This menu only shows 1 additional attribute compared to what you can set when creating a rule.
Parameters
| Property | Description |
|---|---|
| ip-address (required) | Range of IP addresses accepted as clients if empty 0.0.0.0/0 will be used |
| allow-rollover (Default: No) | If set to yes TFTP server will allow the sequence number to roll over when the maximum value is reached. This is used to enable large downloads using the TFTP server. |
| req-filename | Requested filename as a regular expression (regex) if a field is left empty it defaults to .* |
| real-filename | If req-filename and real-filename values are set and valid, the requested filename will be replaced with matched file. This field has to be set. If multiple regex is specified in req-filename, with this field you can set which ones should match, so this rule is validated. The real-filename format for using multiple regex is filename\0\5\6 |
| allow (default: yes) | To allow connection if the above fields are set. if no, a connection will be interrupted |
| read-only (default: no) | Sets if a file can be written to, if set to "yes" write attempt will fail with error |
| hits (read-only) | How many times this access rule entry has been used (read-only) |
Settings
/ip/tftp/settings
This menu contains all TFTP settings.
| Property | Description |
|---|---|
| max-block-size (default:4096) | Maximum accepted block size value. During the transfer negotiation phase, the RouterOS device will not negotiate a larger value than this. |
Regexp
Req-filename field allowed regexp, allowed regexp in this field are:
brackets () - marking subsection:
example 1 a(sd|fg) will match asd or afg
asterisk "*" - match zero or more times preceding symbol:
example 1 a* will match any length name consisting purely of symbols a or no symbols at all
example 2 .* will match any length name, also, empty field
example 3 as*df will match adf, asdf, assdf, asssdf etc.
plus "+" will match one or more times the preceding symbol:
example: as+df will match asdf, assdf etc.
dot "." - matches any symbol:
example as.f will match asdf, asbf ashf etc.
square brackets [] - variation between:
example as[df] will match asd and asf
question mark "?" will match one or no symbols:
example asd?f will match asdf and asf
caret "^" - used at the beginning of the line means that the line starts with;
dollar "$" - means at the end of the line.
Examples
If a file is requested return the file from the store called sata1:
/ip tftp add req-filename=file.txt real-filename=/sata1/file.txt allow=yes read-only=yes
If we want to give out one specific file no matter what the user is requesting:
/ip tftp add req-filename=.* real-filename=/sata1/file.txt allow=yes read-only=yes
If the user requests aaa.bin or bbb.bin then give them ccc.bin:
/ip tftp add req-filename="(aaa.bin)|(bbb.bin)" real-filename="/sata1/ccc.bin\\0" allow=yes read-only=yes
RouterOS receives TFTP requests, but the client gets a transfer timeout?
Some embedded clients request large block sizes and yet do not handle fragmented packets correctly. For these clients, it is recommended to set "max-block-size" on the RouterOS side or "blksize" on Client-side to the value of the smallest MTU on your network minus 32 bytes (20 bytes for IP, 8 for UDP, and 4 for TFTP) and more if you use IP options on your network.