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The AR1200-S considers that the data transmission within a zone is reliable; therefore, it does
not enforce any security policy on the intra-zone data transmission. The AR1200-S verifies the
data and enforces the security policies only when the data flows from one zone to another.
Interzone
Any two zones form an interzone. Each interzone has an independent interzone view. Most
firewall configurations are performed in the interzone views.
Assume that there are zone1 and zone2. In the interzone view, ACL-based packet filtering can
be configured. The configured filtering policy is then enforced on the data transmission between
zone1 and zone2.
Direction
In an interzone, data is transmitted in the inbound or outbound direction.
l
Inbound: indicates that data flows from a zone with lower priority to a zone with higher
priority.
l
Outbound: indicates that data flows from a zone with higher priority to a zone with lower
priority.
ACL-based Packet Filtering
ACL-based packet filtering analyzes the information in the packets to be forwarded, including
source/destination IP addresses, source/destination port numbers, and IP protocol number. The
AR1200-S compares the packet information with the ACL rules and determines whether to
forward or discard the packets.
In addition, the AR1200-S can filter fragmented IP packets to prevent a non-initial fragment
attack.
ASPF
ASPF is applied to the application layer, that is, ASPF is status-based packet filtering. ASPF
detects the application-layer sessions that attempt to pass the firewall, and discards undesired
packets.
The AR1200-S performs ASPF for the File Transfer Protocol (FTP) and Hypertext Transport
Protocol (HTTP) packets.
Blacklist
A blacklist filters packets based on source IP addresses. Compared with the ACL, the blacklist
uses simpler matching fields to implement high-speed packet filtering. Packets from certain IP
addresses can be filtered out.
The firewall dynamically adds IP addresses to the blacklist. The firewall uses packet behavior
to detect an attack from an IP address. If an attack is detected, the firewall adds the IP address
of the attacker to the blacklist so that all packets from the attacker will be discarded.
Huawei AR1200-S Series Enterprise Routers
Configuration Guide - Security
3 Firewall Configuration
Issue 02 (2012-03-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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