Nortel Networks WEB OS 212777 - Manual (Page 144)

Web OS 10.0 Application Guide
144 n Chapter 6: Server Load Balancing
212777-A, February 2002
Using Proxy IP Addresses
Proxy IP addresses are used primarily to eliminate SLB topology restrictions in complex net-
works (see
“Proxy IP Addresses” on page 136 ). Proxy IP addresses can also provide direct
access to real servers.
If the switch port to the client is configured with a proxy IP address, the client can access each
real server directly using the real server’s IP address. The switch port must be connected to the
real server and client processing must be disabled (see the
server and client options
under the /cfg/slb/port command in your Web OS Command Reference).
SLB is still accessed using the virtual server IP address.
Mapping Ports
When SLB is used without proxy IP addresses and without DAM, the Web switch must pro-
cess the server-to-client responses. If a client were to access the real server IP address and port
directly, bypassing client processing, the server-to-client response could be mishandled by
SLB processing as it returns through the Web switch, with the real server IP address getting
remapped back to the virtual server IP address on the Web switch.
First, two port processes must be executed on the real server. One real server port will handle
the direct traffic, and the other will handle SLB traffic. Then, the virtual server port on the Web
switch must be mapped to the proper real server port.
In Figure 6-8 , clients can access SLB services through well-known TCP port 80 at the virtual
server’s IP address. The Web switch behaving like a virtual server is mapped to TCP port 8000
on the real server. For direct access that bypasses the virtual server and SLB, clients can spec-
ify well-known TCP port 80 as the real server’s IP address.
Figure 6-8 Mapped and Nonmapped Server Access
N OTE – Port mapping is supported with DAM when filtering is enabled, a proxy IP address is
configured, or URL parsing is enabled on any switch port.
For more information on how to map a virtual server port to a real server port, see “Mapping
Ports” on page 139 .
80
8000
80
Virtual Server on the
Alteon Web Switch
Real
Server
Client
Network
Direct Access
via Real Server IP & Port
Layer 4 Mapped Access
via Virtual Server IP & Port