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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 23 Configuring Dynamic ARP Inspection
Configuring Dynamic ARP Inspection
Configuring ARP ACLs for Non-DHCP Environments
This procedure shows how to configure dynamic ARP inspection when Switch B shown in
does not support dynamic ARP inspection or DHCP snooping.
If you configure port 1 on Switch A as trusted, a security hole is created because both Switch A and
Host 1 could be attacked by either Switch B or Host 2. To prevent this possibility, you must configure
port 1 on Switch A as untrusted. To permit ARP packets from Host 2, you must set up an ARP ACL and
apply it to VLAN 1. If the IP address of Host 2 is not static (it is impossible to apply the ACL
configuration on Switch A) you must separate Switch A from Switch B at Layer 3 and use a router to
route packets between them.
Beginning in privileged EXEC mode, follow these steps to configure an ARP ACL on Switch A. This
procedure is required in non-DHCP environments.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
arp access-list
acl-name
Define an ARP ACL, and enter ARP access-list configuration
mode. By default, no ARP access lists are defined.
Note
At the end of the ARP access list, there is an implicit
deny
ip any mac any
command.
Step 3
permit ip host
sender-ip
mac host
sender-mac
[
log
]
Permit ARP packets from the specified host (Host 2).
•
For
sender-ip
, enter the IP address of Host 2.
•
For
sender-mac
, enter the MAC address of Host 2.
•
(Optional) Specify
log
to log a packet in the log buffer when
it matches the access control entry (ACE). Matches are logged
if you also configure the
matchlog
keyword in the
ip arp
inspection vlan logging
global configuration command. For
more information, see the
Step 4
exit
Return to global configuration mode.
Содержание Catalyst 3750-E Series
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