Portion of iRule not being processed

Your switch statement that isn't working is trying to match on three strings containing uppercase letters (TID=, FID=, and C=). You are first converting the match string to lower case though ([string tolower [HTTP::query]])

Change your match strings to tid=, fid=, and c= and it should work.

Hmm.....nice catch!

Still doesn't seem to process.

That portion of the iRule works on its own, if I take it out of the nested switch and put each into an if statement....

Have you tried inserting a logging statement before the redirects within this switch statement to verify that the query is matching one of the strings? Or that the host is even matching oldforum.olddomain.com to get to evaluation of the nested switch?

when HTTP_REQUEST {
      switch [string tolower [HTTP::query]] {
            "tid=" {
               log local0. "Query tid= matched"
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid=" {
               log local0. "Query fid= matched"
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c=" {
               log local0. "Query c= matched"
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }

Just tried that - it's not logging. The only way I had it logging before was to put log local0. "Query is [HTTP::query]" before the last curly brace. It knows what the query is, however it doesn't seem to be processing.

For instance - this will log the query:

 These do NOT work
   switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch [string tolower [HTTP::query]] {
            "tid=" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid=" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c=" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
         log local0. "Query is [HTTP::query]"
      }

In the example code you just posted, what gets logged as the query? Does it explicitly match one of the three strings you are matching on?

So the query string is more than just tid=..

Try changing your switch to this:

   switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch [string tolower [HTTP::query]] {
            "tid=*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid=*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c=*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }

Just a thought, but try removing the = from the string to match against:

switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch [string tolower [HTTP::query]] {
            "tid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }

This is what I'm testing with:

when HTTP_REQUEST {
switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch [string tolower [HTTP::query]] {
            "tid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }
   }
}

Sorry, this one should finally work. Your nested switch needs the -glob:

when HTTP_REQUEST {
switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch -glob [string tolower [HTTP::query]] {
            "tid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c*" {
               HTTP::redirect "https://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }
   }
}

I'm coming back to this after a few days - it appears as though the query is not being changed to lowercase, and doesn't process unless I manually change the TID, FID, or C to lower case. Then, the redirect happens properly.

Here is the iRule in its current state:

 Check the Host header value, set to lowercase

switch -glob [string tolower [HTTP::host]] {
      "oldforum.olddomain.com" {
          Check the URI, set to lowercase
         switch -glob [string tolower [HTTP::query]] {
            "tid=*" {
               log local0. "Query is [HTTP::query]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=posts&t=[URI::query [HTTP::uri] tid]"
               return
            }
            "fid=*" {
               log local0. "Query is [HTTP::query]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=topics&f=[URI::query [HTTP::uri] fid]"
               return
            }
            "c=*" {
               log local0. "Query is [HTTP::query]"
               HTTP::redirect "http://newforum.newdomain.com/default.aspx?g=forum&c=[URI::query [HTTP::uri] c]"
               return
            }
         }
      }