308
Chapter 8
Hot Standby Routing Protocol (HSRP)
F I G U R E 8 . 1
Proxy ARP for dial-up connections
First, you should review how Proxy ARP typically functions in dial-up
environments. In the example shown in Figure 8.1, when Host C wants to
send a packet to Host A, it assumes that Host A is on the same segment.
When Host C sends a broadcast ARP for 200.1.1.4, Host B will reply with
its own MAC address. Host C will send packets that are destined for Host
A to Host B's MAC address. Host B will then forward them to A. This style
of Proxy ARP is still prevalent in dial-up environments.
Implementing Proxy ARP with Routers
Proxy ARP with routers works similarly to the example in Figure 8.1, but it
can be configured to provide some fault tolerance. Let's consider Figure 8.2
and how Proxy ARP could be used in this example.
F I G U R E 8 . 2
Proxy ARP with routers
Host A
Host B
Host C
Dial-Up
200.1.1.4
200.1.1.7
200.1.1.6
200.1.1.3
Host C
IP Address 10.1.0.99
Mask 255.255.0.0
Gateway 10.1.0.99
10.1.0.1/16
14.4.4.4/16
10.1.0.2/16
Router B
Router A
Router D
Internet
Copyright ©2000 SYBEX , Inc., Alameda, CA
www.sybex.com