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3 Virus Throttling (Connection-Rate Filtering)
Overview of Connection-Rate Filtering  . . . . . . . . . . . . . . . . . . . . . . . . .  3-1
Features and Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
General Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3-3
Filtering Options   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3-3
Sensitivity to Connection Rate Detection  . . . . . . . . . . . . . . . . . . . .  3-4
Application Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3-4
Operating Rules  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Unblocking a Currently Blocked Host   . . . . . . . . . . . . . . . . . . . . . . 3-6
General Configuration Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
For a network that is relatively attack-free:   . . . . . . . . . . . . . . . . . . . . .  3-7
For a network that appears to be under significant attack: . . . . . . . . . 3-8
Configuring Connection-Rate Filtering  . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Global and Per-Port Configuration  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3-9
Enabling Connection-Rate Filtering and Configuring
Sensitivity  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Configuring the Per-Port Filtering Mode   . . . . . . . . . . . . . . . . . . .  3-11
Example of a Basic Connection-Rate Filtering Configuration . .  3-12
Viewing and Managing Connection-Rate Status  . . . . . . . . . . . . . . . . . 3-14
Viewing Connection-Rate Configuration   . . . . . . . . . . . . . . . . . . . 3-14
Listing Currently-Blocked Hosts  . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
Unblocking Currently-Blocked Hosts  . . . . . . . . . . . . . . . . . . . . . .  3-15
Configuring and Applying Connection-Rate ACLs  . . . . . . . . . . . . . .  3-17
Connection-Rate ACL Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
Configuring a Connection-Rate ACL Using 
Source IP Address Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
Configuring a Connection-Rate ACL Using UDP/TCP Criteria  . . . . . 3-21
Applying Connection-Rate ACLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  3-24
Using CIDR Notation To Enter the ACE Mask  . . . . . . . . . . . . . . . . . .  3-24
Example of Using an ACL in a Connection-Rate Configuration  . . . . 3-25
Connection-Rate ACL Operating Notes  . . . . . . . . . . . . . . . . . . . . . . . . 3-27