Insert client IP?

So I'm trying to insert the original client IP in a header so I can use that in apache logging. I was originally using x-forwarded-for, but that screws things up since x-forwarded-for can be a comma-separated list of ips.

 

 

My rule looks like this:

 

when HTTP_REQUEST {

 

HTTP::header insert ORIG_IP [IP::remote_addr]

 

}

 

 

that works for a majority of connections, but if I look at the ltm logs, I see a TON of

 

Aug 31 13:11:08 tmm tmm[818]: 01220001:3: TCL error: Rule insert_orig_ip EQUEST> - Operation not supported (line 1) invoked from within "HTTP::header

 

insert ORIG_IP [IP::remote_addr]"

 

 

I'm not sure what operation isn't supported here... Am I missing something? Again, this doesn't seem to happen on EVERY request, but a fair amount do...