HP PROCURVE 2910AL, Руководство по обеспечению безопасности доступа

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IPv4 Access Control Lists (ACLs)
Configuring and Assigning an IPv4 ACL
For example, suppose that you have applied the ACL shown in figure 9-10 to
inbound IPv4 traffic on VLAN 1 (the default VLAN):
ip access-list extended "Sample-List-2"
10 deny ip 10.28.235.10 0.0.0.0 0.0.0.0 255.255.255.255
20 deny ip 10.28.245.89 0.0.0.0 0.0.0.0 255.255.255.255
30 permit tcp 10.28.18.100 0.0.0.0 10.28.237.1 0.0.0.0
40 deny tcp 10.28.18.100 0.0.0.0 0.0.0.0 255.255.255.255
50 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255
(Implicit Deny)
exit
After the last explicit ACE there is always an Implicit Deny. However, in this case it will not be used because
the last,
permit ip
ACL allows all IPv4 packets that earlier ACEs have not already permitted or denied.
Source Address
DestinationAddress
Mask
Mask
Figure 9-10. Example of a Standard ACL that Permits All IPv4 Traffic Not Implicitly Denied
Table 9-4. Effect of the Above ACL on Inbound IPv4 Traffic in the Assigned VLAN
Line # Action
n/a Shows type ( extended ) and ID (Sample-List-2).
10 A packet from SA 10.28.235.10 will be denied (dropped). This ACE filters out all packets received from
10.28.235.10. As a result, IPv4 traffic from that device will not be allowed and packets from that device will not
be compared against any later entries in the list.
20 A packet from SA 10.28.245.89 will be denied (dropped). This ACE filters out all packets received from
10.28.245.89. As the result, IPv4 traffic from that device will not be allowed and packets from that device will
not be compared against any later entries in the list.
30 A TCP packet from SA 10.28.18.100 with a DA of 10.28.237.1 will be permitted (forwarded). Since no earlier ACEs
in the list have filtered TCP packets from 10.28.18.100 and destined for 10.28.237.1, the switch will use this ACE
to evaluate such packets. Any packets that meet this criteria will be forwarded. (Any packets that do not meet
this TCP source-destination criteria are not affected by this ACE.)
40 A TCP packet from source address 10.28.18.100 to any destination address will be denied (dropped). Since, in
this example, the intent is to block TCP traffic from 10.28.18.100 to any destination except the destination stated
in the ACE at line 30, this ACE must follow the ACE at line 30. (If their relative positions were exchanged, all TCP
traffic from 10.28.18.100 would be dropped, including the traffic for the 10.28.18.1 destination.)
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