From: Mark, Detrick (mdetrick@xxxxxxxxx)
Date: Mon Jun 21 1999 - 13:47:09 GMT-3
In addition to the great answer below...
The default-gateway setting on the PC tells the PC to send an ARP for the
local MAC of the destination machine on its own subnet or to send to the MAC
of the IP address of the default-gateway because the machine is not on the
local subnet. Determining if the machine is on the local subnet is
accomplished by a calulation using the subnet mask and IP address of the PC.
Example:
If you wanted to use the router as a proxy-arp instead of gateway on the PC,
and the enterprise was addressed using private 10. A computer on segment
10.0.0.0/24 may be configured with i.e. 10.0.0.56/8 (opening up the subnet
mask to make the PC think all the subnets are local, router is configured
with 10.0.0.1/24) and send all 10 traffic out on its local subnet. This
might work for all 10 addressing within the enterprise, but resolution to
anything other than 10.0.0.0 (outside the enterprise)would fail because the
PC would want to send to the gateway which has not been configured.
Mark Detrick
DSL Business Unit
Cisco Systems
2569 McCabe Way
Irvine, CA 92614
----- Original Message -----
From: Higgins, Andrew <Andrew.Higgins@sequoia.panurgy.com>
To: 'jbxu' <jbxu@www3.cea.online.sh.cn>; <ccielab@groupstudy.com>
Sent: Saturday, June 19, 1999 7:30 PM
Subject: RE: proxy-arp
> Not necessarily. For proxy-arp to work, a device needs to arp on the
local
> subnet with a destination address that is not part of the local subnet. I
> have seen proxy-arp used at a client site where several Unix workstations
> had the incorrect subnet mask configured and they were sending arps on the
> local subnet for devices that were actually on remote subnets. The router
> recognized the arps were for remote subnets and replied to the
workstations
> with its own mac address, then passed to data along to the remote device.
>
> Andrew
>
> -----Original Message-----
> From: jbxu [mailto:jbxu@www3.cea.online.sh.cn]
> Sent: Saturday, June 19, 1999 10:13 PM
> To: ccielab@groupstudy.com
> Subject: proxy-arp
>
>
> question:
> I think "proxy-arp" is to help pc with no knowledge of routing
> to determine the media address of pc on other networks.I know the proxy
> arp on the cisco router is enabled by default.
> Is this mean I can ping a pc on another network from my pc without
> defult-gateway.
> anyone have the experience to use the proxy-arp?
>
> thanks in advance
>
>
> jbxu
> jbxu@mail.cea.online.sh.cn
>
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