This preview shows page 1. Sign up to view the full content.
Unformatted text preview: n Section 3.8 that the destination address
of the dialup SLIP link, as shown by the ifconfig command, was 22.214.171.124. The Net-Blazer doesn't
require an IP address for its end of each dialup SLIP link. (Doing so would use up more IP addresses.) Instead, it
determines which dialup host is sending it packets by which serial interface the packet arrives on, so there's no file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/arp_addr.htm (9 of 12) [12/09/2001 14.46.39] Chapter 4. ARP: Address Resolution Protocol need for each dialup host to use a unique IP address for its link to the router. All the dialup hosts use
126.96.36.199 as the destination address for their SLIP link.
Proxy ARP handles the delivery of datagrams to the router sun, but how are the other hosts on the subnet
140.252.13 handled? Routing must be used to direct datagrams to the other hosts. Specifically, routing table
entries must be made somewhere on the 140.252 network that point all datagrams destined to either the subnet
140.252.13, or the specific hosts on that subnet, to the router netb. This router then knows how to get the
datagrams to their final destination, by sending them through the router sun.
Proxy ARP is also called promiscuous ARP or the ARP hack. These names are from another use of proxy ARP: to
hide two physical networks from each other, with a router between the two. In this case both physical networks
can use the same network ID as long as the router in the middle is configured as a proxy ARP agent to respond to
ARP requests on one network for a host on the other network. This technique has been used in the past to "hide" a
group of hosts with older implementations of TCP/IP on a separate physical cable. Two common reasons for
separating these older hosts are their inability to handle subnetting and their use of the older broadcasting address
(a host ID of all zero bits, instead of the current standard of a host ID with all one bits). 4.7 Gratuitous ARP
Another feature of ARP that we can watch is called gratuitous ARP. It occurs when a host sends an ARP request
looking for i...
View Full Document
This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12