Internal Firewall - 3Com VCX v7111 User Manual

Internal Firewall

The V7111 gateway accommodates an internal access list facility, allowing the security
administrator to define network traffic filtering rules. The access list provides the following
features:
Block traffic from known malicious sources
Only allow traffic from known friendly sources, and block all others
Mix allowed and blocked network sources
Limit traffic to a predefined rate (blocking the excess)
Limit traffic to specific protocols, and specific port ranges on the device
The access list consists of a table with up to 50 ordered lines. For each packet received on
the network interface, the table is scanned from the top until a matching rule is found (or the
table end is reached). This rule can either block the packet or allow it; however it is important
to note that subsequent rules are not scanned. If the table end is reached without a match,
the packet is accepted.
Each rule is composed of the following fields (described in
IP address (or DNS name) of source network
IP network mask
Destination UDP/TCP ports (on this device)
Protocol type
Maximum packet size, byte rate per second, and allowed data burst
Action upon match (allow or block)
Figure 134 shows an example of an access list definition using ini file:
Figure 134 Example of an Access List Definition using ini File
[ ACCESSLIST ]
FORMAT AccessList_Index = AccessList_Source_IP, AccessList_Net_Mask,
AccessList_Start_Port, AccessList_End_Port, AccessList_Protocol,
AccessList_Packet_Size, AccessList_Byte_Rate, AccessList_Byte_Burst,
AccessList_Allow_Type;
AccessList 10 = mgmt.customer.com, 255.255.255.255, 0, 80, tcp, 0, 0, 0,
allow ;
AccessList 15 = 192.0.0.0, 255.0.0.0, 0, 65535, any, 0, 40000, 50000,
block ;
AccessList 20 = 10.31.4.0, 255.255.255.0, 4000, 9000, any, 0, 0, 0, block
;
AccessList 22 = 10.4.0.0, 255.255.0.0, 4000, 9000, any, 0, 0, 0, block ;
[ \ACCESSLIST ]
342
Table 63):
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3Com VCX V7111 VoIP Gateway User Guide