From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sun Nov 12 2006 - 22:12:45 ART
For one what is the layer 3 address of a host when it is attempting to
get its IP address from a DHCP server?
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
________________________________
From: Adhu Ajit [mailto:adhu_ajit@yahoo.com]
Sent: Sunday, November 12, 2006 4:46 PM
To: Brian Dennis; ccielab@groupstudy.com
Subject: RE: host 0.0.0.0
Brian, thanks. I'm wondering what purpose the following ACE serves:
permit ip host 0.0.0.0
This is a question to me because I'm wondering if any IP stack would
allow itself to be configured as IP address 0.0.0.0. As you know, Cisco
routers dont allow this. When that is the case, what is the purpose of
the above mentioned ACE.
Thanks.
Brian Dennis <bdennis@internetworkexpert.com> wrote:
No, "host" is just a simplified way to saying the wildcard mask
is
0.0.0.0.
These two access-lists are the same:
access-list 100 permit ip 172.16.1.1 0.0.0.0 any
access-list 100 permit ip host 172.16.1.1 any
In fact if you enter the command in the first format (no host
keyword)
the router will change it to the second format.
Rack1R6(config)#access-list 100 permit ip 172.16.1.1 0.0.0.0 any
Rack1R6(config)#do sho run | in access-list 100
access-list 100 permit ip host 172.16.1.1 any
Rack1R6(config)#
Here is the DocCD link for the access-list command:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hi
ap_r/apl_a1h.htm#wp1131458
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
Adhu Ajit
Sent: Sunday, November 12, 2006 2:52 PM
To: ccielab@groupstudy.com
Subject: host 0.0.0.0
Is there a special meaning when someone writes:
permit ip host 0.0.0.0
or does it just mean what I think it means.
What I think it means is:
Permit any host whose source ip address is 0.0.0.0. But I wonder
if
any IP stack will allow itself to be configured with 0.0.0.0 as
the IP
address. Then again, I also start wondering on what was the
intention of
the afore mentioned ACL entry ???!!!
(Folks, this is NOT permit ip 0.0.0.0 255.255.255.255. Here it
is
"host" followed by no wildcarded bits)
Bye.
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