You can use substring to do that. Here is an example of it in use:
match if substring (option dhcp-client-identifier, 1, 3) = "RAS";
see also `man dhcp-eval`
substring (data-expr, offset, length)
The substring operator evaluates the data expression and returns the
substring of the result of that evaluation that starts offset bytes from
the beginning, continuing for length bytes. Offset and length
are both numeric expressions. If data-expr, offset or length evaluate to
null, then the result is also null. If offset is greater than or
equal to the length of the evaluated data, then a zero-length data string
is returned. If length is greater then the remaining length of the
evaluated data after offset, then a data string containing all data from
offset to the end of the evaluated data is returned.
----- Original Message -----
> From: "egor grijuc" <[email protected]>
> To: "kea-users" <[email protected]>
> Sent: Wednesday, January 26, 2022 4:40:26 AM
> Subject: [Kea-users] Globally cut circuit id option
> Hello.
> We faced a problem with some old equipment.
> We use host database for host reservation
> We make reservation via API.
> In table “host” we use dhcp_identifier_type =2 to match circuit id.
> It works but we have some old equipment that adds some kind of prefix to
> circuit
> id option.
> For example, on switch circuit id was configured to “CHN540579” but on packet
> capture we see that switch adds some “prefix”
> Part from capture:
> Agent-Information Option 82, length 23:
> Circuit-ID SubOption 1, length 11: ^A^ICHN540579
> Question: is it possible to globally cut circuit id optin from end to 9
> characters?
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