Hmm... That's interesting. I'm trying to figure it out. Say, on my office
network, my default gateway is something like 10.0.0.32 because we're using
private addresses and NAT. When I travel, would the router in the hotel
respond to my ARP for 10.0.0.32?? Would the router think that it can reach
network 10.0.0.0?
And, let's say that I don't use private addresses on my office network
(which I don't). Let's say the default gateway is 138.1.80.193. Would the
hotel router respond to my ARP for 138.1.80.193? Would the router think
that it can reach network 138.1.0.0?
I would hate to be the desk clerk responding to questions about this! ;-)
Priscilla
At 10:56 AM 5/24/01, [EMAIL PROTECTED] wrote:
>Proxy-Arp Lives!
>
>I have to add that as I understand it proxy arp and nat are how hotels offer
>internet connectivity. Take a laptop with any ip address configured plug it
>in and it will arp for its default gateway. The router with proxy arp will
>answer as the default gateways mac address. Then using a wide scope for nat
>(the scope would be the entire ip address range) the hotel can provide
>internet connectivity to a client with any configured ip address and
>gateway.
>
>Dean Whitley
>
>-----Original Message-----
>From: Hire, Ejay [mailto:[EMAIL PROTECTED]]
>Sent: Thursday, May 24, 2001 10:32 AM
>To: [EMAIL PROTECTED]
>Subject: RE: ARP versus Proxy-arp [7:5664]
>
>
>Proxy arp isn't dead, it is still in use very frequently on dial-up links.
>If you get a chance, dial-up to earthlink and run winipcfg. You'll see that
>your default gateway is actually set to yourself. Their is a reasonable
>explanation of this behavior in the Sybex CCNP switch 2.0 chapter on
>redundancy.
>
>-EH
>
>-----Original Message-----
>From: Chuck Larrieu [mailto:[EMAIL PROTECTED]]
>Sent: Wednesday, May 23, 2001 10:37 PM
>To: [EMAIL PROTECTED]
>Subject: ARP versus Proxy-arp [7:5664]
>
>
>At the risk of becoming another Bob Vance......
>
>I'm reading Doug Comer's TCP/IP reference, on the assumption that it can't
>hurt to really get into how TCP/IP works.
>
>Proxy-arp versus normal arp.
>
>A host does not know the physical address of another host so it sends out an
>ARP request. If the host in question lies on another network, a router
>responds to that request. Proxy ARP, correct?
>
>A host through it's TCP stack does the XOR and determines that a host lies
>on another network. The host therefore sends the packet to the device
>indicated as its default gateway in its configuration. It sends an ARP
>request for the MAC of the default gateway. Normal ARP?
>
>So in other words, proxy arp may be viewed as something of an obsolete
>protocol / operation in that most modern TCP stacks contain the mechanisms
>for doing the network XOR determination, and then using the default gateway.
>A modern stack would recognize that a host is on a different network and go
>the default gateway route, so to speak.
>
>In other words, the necessity for proxy arp is eliminated for the most part
>because of the default gateway concept and the modern TCP stack.
>
>Has it sunk through this thick head finally?
>
>PS Comer states that proxy arp is aka arp hack. :->
>
>Chuck
>
>One IOS to forward them all.
>One IOS to find them.
>One IOS to summarize them all
>And in the routing table bind them.
>
>-JRR Chambers-
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
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