Log option (18) Interface-Id in DHCPv6 failed

[Niall O'Reilly]

At Mon, 23 Feb 2015 12:40:31 +0100,
Darko Bezjak wrote:
> 
> log(info,concat("Interface-ID: " , option dhcp6.interface-id));

  From `man dhcp-eval`:

   concat (data-expr1, ..., data-exprN)
     The expressions are evaluated, and the results of each evaluation are
     concatenated in the sequence that the subexpressions are listed.   If
     any  subexpression evaluates to null, the result of the concatenation
     is null.

  I suspect that the option is not being set as you expect, so that
  the second argument to log() becomes a null string.  The following
  code should alow you confirm.

  log(info,concat("Interface-ID: ",
                  pick-first-value((option dhcp6.interface-id),
		                   "(missing)")));

  I hope this helps.
  Niall O'Reilly