Forum Discussion
nyumx_68500
Nimbostratus
NimbostratusGTM Load Balancing of pool of external DNS servers won't work
Hello,
I'm configuring my Global Traffic Manager to deal with a situation like this.
test.com is the top domain name.
www.test.com is address of the web server which is wide-ip, which should be load balanced with GTM.
besides that, there are so many standalone, single servers those I don't have to load balance.
Because it is no good to load balance single server.
such as a.www.test.com, b.www.test.com, c.www.test.com and so on.
I configured my GTM referring to the guide "Global Traffic Manager Implementations".
I used the scenario named "Load Balancing Non-Wide IP Traffic to a Pool of DNS Servers".
This is my explanatly environment.
A client is 192.168.0.11
B GTM is 172.16.0.11
C Authoritative DNS is 10.0.0.11
In this environment, I'm facing strange behavior like this.
In client A, do "$dig @172.16.0.11 a.www.test.com"
a.www.test.com is not the Wide IP and it should be forwarded.
A client sends a request to B GTM. (source and destination address in packet header is 192.168.0.11->172.16.0.11)
B GTM sends a request to C Authoritative DNS (packet header is 192.168.0.11->10.0.0.11)
* GTM sends the spoofed packet here.
C Authoritative DNS sends a answer to A client. (packet header is 10.0.0.11->192.168.0.11)
Finally client A got error like this,
;;reply from unexpected source: 10.0.0.1153, expected 172.16.0.1153
Is this the designed behavior of GTM ?
(tmos) list /gtm listener
gtm listener DNS_listener {
address 172.16.0.11
ip-protocol udp
pool DNS_pool
}
(tmos) list /ltm pool
ltm pool DNS_pool {
members {
10.0.0.11:domain {}
}
}
Haarith_DevarajShouldnt make a difference, but i am curios if you have the option for GTMD to set recursion.
Should be under General properties -> Global traffic --> General.
If you are testing with the unit, give that a shot.
nyumx_68500Haarith,
Thank you for your replying,
But I resolved this problem finally.
I found I had to add "snat automap" settings in ltm virtual "DNS_listener".
With this settings, I can resolve desired results.
Packet flow was like this.
(without snat automap)
[client]->[GTM]->[external DNS server]->[client]
- response packet was dropped in FW&LB between [external DNS server] and [client]
OR
-[client] dropped response packet.
(with snat automap)
[client]->[GTM]->[external DNS server]->[GTM]->[client](tmos) list /ltm virtual DNS_listener ltm virtual DNS_listener { destination 172.16.0.11:domain ip-protocol udp mask 255.255.255.255 pool DNS_pool profiles { dns { } udp_gtm_dns { } } snat automap translate-port disabled }- Haarith_DevarajCool, thanks for posting the solution.
pjcampbell_7243Cirrus
I am having similar problems, but my VIP and pool members are both local. This is on an LTM. Any ideas? I'm using snat auto map and udp_gtm_dns. I don't have a "DNS" profile. Do I need to make one? What else am I forgetting?
virtual primary-dns {
snat automap
pool primary-dns
destination xyz:domain
ip protocol udp
profiles udp_gtm_dns
}