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ARP Proxy concept from two different resources

“Data Communications and Networking” 3ed by Forouzan page 518 says:

[[[Case 2 :

The sender is a host and wants to send a packet to another hosts on another network. In this case, the host looks at its routing table and finds the ip address of the next hop (router) for this destination. The ip address of the router becomes the ip address that must be mapped to a physical address]]].

See the link below for case 2

http://img45.imageshack.us/img45/3345/case020vv.jpg

1- Shouldn’t he say that : “The mac address of the router becomes the mac address that must be mapped to the ip address” instead of "The ip address of the router becomes the ip address that must be mapped to a physical address" ?

comparing with the link below:

http://www.cisco.com/warp/public/105/5.html

[[[Note: Multiple IP addresses are mapped to a single MAC address (the router's MAC address), indicating that proxy ARP is in use]]].

2- Target MAC address within ARP request packet is all 0s, this ARP packet is encapsulated directly inot data link frame.

MAC address for the same Target within data link farme is all Fs.

The same book depicts the MAC address within data link frame all 1s,,,Is this acceptable ?

1 ACCEPTED SOLUTION

Accepted Solutions

Re: ARP Proxy concept from two different resources

Hi Zillah,

1) You are right saying that when we say proxy arp someone else in the network send its own mac address to map the destination ip address which does not belong to the one who send its mac address.

So your statement Shouldn’t he say that : “The mac address of the router becomes the mac address that must be mapped to the ip address" is true.

2) The destination address of the ARP is a broadcast address which is all 1's

http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/arp.html

But even if we say all F instead of all 1 in broadcast mac address it is one of the same thing

http://www.webopedia.com/TERM/B/broadcast_address.html

http://www.bellevuelinux.org/broadcast_address.html

So what I want to say is broadcast mac address can be represented by both the ways all 1's or all F's.

HTH, if yes please rate the post.

Ankur

3 REPLIES

Re: ARP Proxy concept from two different resources

Hi Zillah,

1) You are right saying that when we say proxy arp someone else in the network send its own mac address to map the destination ip address which does not belong to the one who send its mac address.

So your statement Shouldn’t he say that : “The mac address of the router becomes the mac address that must be mapped to the ip address" is true.

2) The destination address of the ARP is a broadcast address which is all 1's

http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/arp.html

But even if we say all F instead of all 1 in broadcast mac address it is one of the same thing

http://www.webopedia.com/TERM/B/broadcast_address.html

http://www.bellevuelinux.org/broadcast_address.html

So what I want to say is broadcast mac address can be represented by both the ways all 1's or all F's.

HTH, if yes please rate the post.

Ankur

New Member

Re: ARP Proxy concept from two different resources

Thanks Ankur

[[[So your statement Shouldn’t he say that : “The mac address of the router becomes the mac address that must be mapped to the ip address" is true.]]]

Does that mean there is a sort of typo in the explaination of the book ?

Re: ARP Proxy concept from two different resources

HI Zillah,

Yes there can be a type error in the book.

In proxy ARP the mac address of the router becomes the mac address that must be mapped to the destination ip address which is not in my network.

HTH, if yes please rate the post.

Ankur

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