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Source IP preservation on backend server’s for SMTP relay traffic (port:tcp 25)


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Hi Team,

We have server team requirement to preserve the source (client) IP's on SMTP sevrers. Currently servers for both external and internal source IPs seen as Subnet IP of nescaler  LB on backservers.  

 

Article: https://support.citrix.com/article/CTX205670/how-to-enable-client-ip-in-tcpip-option-of-netscaler

I also referred this article and followed steps mentioned in it. I tested in lab LB and I was able to see additional len =52 packet after tcp 3 way handshake ACK packet. but application is getting an error and it seems like its breaking. 

 

Can you please help me how can fix this issue ?

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5 hours ago, Girish Bammanawadi1709162406 said:

Article: https://support.citrix.com/article/CTX205670/how-to-enable-client-ip-in-tcpip-option-of-netscaler

I also referred this article and followed steps mentioned in it. I tested in lab LB and I was able to see additional len =52 packet after tcp 3 way handshake ACK packet. but application is getting an error and it seems like its breaking. 

 

Can you please help me how can fix this issue ?

Does your mail server understand this extra TCP packet?

 

I usually use SIP mode. In SIP-mode, the ADC will send packets from a fake IP, i.e. client's IP. Therefore, the mail server will simply "think" to talk to the client, and therefore log client's IP. The only issue to overcome is asymetric routing. You have to make sure packets sent from mail server to the client arrive on the ADC. This can be done using Policy based routing, or by setting the ADC as a default gateway for the mail server

https://docs.citrix.com/en-us/citrix-adc/current-release/networking/ip-addressing/enabling-use-source-ip-mode.html

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