691
MS Exchange Routing
Medium RiskTCP — Email
Port Overview
Port Number
691
Service Name
MS Exchange Routing
Transport Protocol
TCP
Category
Email
Security Risk
Medium
Port Range
Well-Known (0-1023)
What is Port 691?
Microsoft Exchange Server Link State routing protocol, used internally by Exchange 2000/2003 servers for routing topology. Deprecated in Exchange 2007.
TCP
Email
Security Considerations
Port 691 (MS Exchange Routing) is classified as medium risk. While this service is commonly exposed, consider using encrypted alternatives where available.
Recommendation: Keep the service updated. Monitor logs for unusual activity.