SNMP Traps, SMTP and SYSLOG all sending from incorrect interface.

Question

Came across a interesting issue when specifying the outbound interface to internal network for SNMP Traps, SMTP and SYSLOG they would still come out over the external interface. Searched for hours on the forums without much luck. 
 This was seemingly caused by the fact we use Uplink Balancing. 
 To resolve this issue, simply create Multipath rules for the affected services to force them out the correct interface. 
 
 I hope this helps any others facing the same issue.

Oliver Smart · Accepted Answer

Good morning Bob, 
 
 Yes, I can confirm the internal interface has a default gateway configured. It was a really strange issue and affected multiple services. With SNMP traps, I set the outbound interface to internal but even with that setting in place it was going out the external interface, I was left scratching my head for days but I assume there is a overriding setting somewhere else that was forcing the use of the external interface. Fortunately, configuring a multipath route Ext1 &rarr; SNMP-Traps &rarr; Internal Server Name &rarr; Internal resolved the issue, We have also configured multipath routes for SYSLOG and SMTP for the same purpose. 
 
 Regard, 
 Oliver

Oliver Smart · Answer

We have included this for BCP purposes, if both external links go down, it will route traffic back through the internal interface and out a DIA link.