servfail response message question

[RYAN CHERVENKA]

I currently have a domain example.com authoritative on my Ubuntu server and it is delegating gslb.example.com to my load balancer. 

www.example.com is a CNAME for www.gslb.example.com 
Gslb.example.com has an NS record pointing to the LB

Client sends query for www.example.com to Ubuntu DNS server. The Ubuntu DNS server sends a query to the load balancer for www.gslb.example.com and the LB responds to the Ubuntu DNS server with the right A record in the answer section. However, the Ubuntu server responds to the client with servfail. 

When I look at the pcap from the Ubuntu server, the LB is responding to it with the correct IP but the dig response from the Ubuntu server to the client shows "no servers could be reached" when I dig against the Ubuntu. I also see the same message in the dns response in the pcap (obviously).

Ryans-MacBook-Pro:~ ryanc$ dig @10.10.1.50 www.example.com <-me querying the Ubuntu for www.example.com

; <<>> DiG 9.8.3-P1 <<>> @10.10.1.50 www.example.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached


Do you have any ideas as to why this is happening?

Ryan Chervenka
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