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Date: | Mon, 7 May 2012 22:48:42 -0400 |
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Btw, I just checked my old notes, which I copied and pasted below.
Hopefully this will shed some light into your issue:
> 1. The server first checks its routing table to see which router
> provides the next hop to the destination network.
> 2. If there is a valid router, let's say with an IP address of
> 192.168.1.1, the server checks its ARP table to see whether it has the MAC
> address of the router's NIC. You could very loosely view this as the server
> trying to find the Ethernet serial number of the next hop router on the
> local network, thereby ensuring that the packet is sent to the correct
> device.
> 3. If there is an ARP entry, the server sends the IP packet to its NIC
> and tells the NIC to encapsulate the packet in a frame destined for the MAC
> address of the router.
> 4. If there is no ARP entry, the server issues an ARP request asking
> that router 192.168.1.1 respond with its MAC address so that the delivery
> can be made. When a reply is received, the packet is sent and the ARP table
> is subsequently updated with the new MAC address.
> 5. As each router in the path receives the packet, it plucks the IP
> packet out of the Ethernet frame, leaving the MAC information behind. It
> then inspects the destination IP address in the packet and use its routing
> table to determine the IP address of the next router on the path to this
> destination.
> 6. The router then uses the "ARP-ing" process to get the MAC address
> of this next hop router. It then reencapsulates the packet in an Ethernet
> frame with the new MAC address and sends the frame to the next hop router.
> This relaying process continues until the packet reaches the target
> computer.
> 7. If the target server is on the same network as the source server, a
> similar process occurs. The ARP table is queried. If no entry is available,
> an ARP request is made asking the target server for its MAC address. Once a
> reply is received, the packet is sent and the ARP table is subsequently
> updated with the new MAC address.
> 8. The server will not send the data to its intended destination
> unless it has an entry in its ARP table for the next hop. If it doesn't,
> the application needing to communicate will issue a timeout or time
> exceeded error.
> 9. As can be expected, the ARP table contains only the MAC addresses
> of devices on the locally connected network. ARP entries are not permanent
> and will be erased after a fixed period of time depending on the operating
> system used.
>
>
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