Coyote Point Systems Equalizer, Installation And Administration Manual

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Appendix B:Using Reserved IP Addresses
102 Equalizer Installation and Administration Guide
Reserved IP Addresses
Equalizer supports placing servers on reserved, non-routable networks such as the class A
network 10.0.0.0 and the class C network 192.168.2.0. In environments where the
conservation of IP addresses is important, using reserved IP addresses can minimize the
number of “real” IP addresses needed.
For example, an ISP hosting several hundred unique web sites replicated on three servers
might not want to assign real IP addresses for all of them because each virtual cluster
would consume four addresses: three on the back-end servers and one for the virtual
cluster. In this case, the ISP might use 10.0.0.0 (the now-defunct Arpanet) as the internal
network and assign virtual server addresses out this network for the servers.
Figure 65 Reserved Internal Network
If servers placed on a non-routable network will need to communicate with hosts on the
Internet for any reason (such as performing DNS resolution or sending email), you need to
configure Equalizer to perform outbound NAT (network address translation). When
outbound NAT is enabled, Equalizer translates connections originating from the servers on
the reserved network so that external hosts won’t see packets originating from non-
routable addresses.
Note – Due to the additional overhead introduced by enabling outbound NAT, using reserved
internal networks should be approached with caution.
Server 2 Server 3
.10 .11 .12
Server 1
Equalizer
Router .1
External Network
Internal Network
199.146.85.0
10.0.0.0
FXP0 .2
FXP1 .1
Client
Internet
Client
NameServer