[squid-users] how to block machines with MAC Address

Hi
I have configure squid stable12 for X-Forwarded-For
below is acl i created.
i am blocking machines with MAC Address but unable to block it dont know
why.
I can block with IPAddress but not with MAC Address any reason.

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acl our_network src 192.168.1.0/24 192.168.3.0/24 172.27.0.0/16
192.168.100.0/24 172.16.0.0/16 172.20.0.0/16
acl LibaccessSite url_regex "/etc/squid/library.txt"
acl Libipblock arp 00:00:E8:3C:FF:5D 00:80:C8:01:69:95 00:E0:50:00:69:17
00:80:AD:83:7E:EE 00:50:BA:D9:17:08
acl Libportblock port 80
acl LibWorkHrs time M T W H F A 08:00-18:00

acl yahoo_msg_url url_regex "/etc/squid/yahoomsg.txt"

acl localhost src 127.0.0.1
acl proxy src 192.168.1.1
acl my_other_proxy srcdomain .nio.org
follow_x_forwarded_for allow localhost
follow_x_forwarded_for allow proxy
follow_x_forwarded_for allow my_other_proxy

acl_uses_indirect_client on
delay_pool_uses_indirect_client on
log_uses_indirect_client on

http_access allow manager localhost
http_access allow proxy
http_access allow Libipblock Libportblock LibWorkHrs LibaccessSite
http_access deny Libipblock
http_access allow our_network Safe_ports
http_access deny all

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Thanks & Regards,
Remy Almeida
NIO System Admin
Ph Office: +91-0832-2450421
         Cell: 9822586093
Received on Mon Jan 09 2006 - 02:26:35 MST