Avocent Cyclades-PR4000 installation manual Filters and Rules 127

Cyclades-PR4000

Steps necessary to activate filtering on the exterior router in the example:

1There are two interfaces with two directions each. Filtering on link 1 requires the creation of two rule lists, called exterior_in and exterior_out. Create them using the menu CONFIG =>RULES LIST =>IP =>ADD RULE LIST and the following parameters:

Rule List Type = Filter Default Scope = Deny Linked Rule List Name = None

2Create the rules for each rule list in the order in which they should be evaluated. The order is important and mis-ordering the rules can cause unexpected results. This is done in the menu CONFIG =>RULES LIST =>IP =>CONFIGURE RULES. The parameters for rules 0 and 1 in the example are shown in Figure 12.4.

3Link the rule lists to the respective interface parameters in the menu CONFIG =>INTERFACE =><INTERFACE> =>NETWORK PROTOCOL =>INCOMING/ OUTGOING RULE LIST NAME. exterior_in should be set as the incoming rule list name and exterior_out should be set as the outgoing rule list name.

Exterior_in, rule 0, allows a remote computer to connect to the bastion host using the TCP protocol on its SMTP port. Exterior_out, rule 0, allows the Bastion Server to RESPOND to the connection started by the remote computer. To send e-mail out, two more rules would be needed. If all the router needs to do is receive e- mail, the configuration is done. If not, other “holes” must be created in the deny ball.

Chapter 14 - Filters and Rules 127