Lab
11.3.4: Configuring TCP Load Distribution with Frame Relay
Objectives:
To configure a Frame Relay connection between our WebHeads
router in Orlando and the ISP's router in Houston, and configure
TCP Load Distribution on the WebHeads router.
Scenario:
We work for a company that hosts web sites. The company, "WebHeads"
currently has only one main web server, hosting a large number of
web sites. The web sites hosted at WebHeads are growing increasingly
more popular with Internet users. We have done testing and found
that the frame relay link and our router can easily handle more
information, but our server is having a hard time keeping up with
the requests for web pages. One option is to buy a new more powerful
web server, but our superiors are afraid of the loss of business if
the server ever failed, and the down time would cost the WebHeads
company a lot of money. Our solution instead was to buy multiple
servers which have duplicate information loaded on them, that way if
one should ever fail, the others would still be up and operating,
and the company would not have any down time or loss of revenue.
Since the original server was at IP address 4.4.4.4, we want to keep
that same address for all of the servers in use. The way that we can
accomplish this is through the use of Load Distribution on our
router. It is our job to set up this connection and to correctly
configure Load Distribution on the WebHeads router.
Notes:
Lab Tasks:
Cable the lab as shown in the diagram.
The next task is to set up the routers and Frame Relay
connection as in previous labs:
Configure IGRP routing with the AS# 707.
Configure the correct IP addresses on each of the routers.
Configure the encapsulation type, DLCI, LMI type, and any
frame relay maps.
Note: Houston, use DLCI 17 to get to WebHeads. WebHeads use
DLCI 18 to get to Houston.
Don't forget the
no shutdown
command on the interfaces.
Before configuring Load distribution on the WebHeads router,
test your configurations by pinging the other router. This way you
are insuring that your basic configuration is correct before
changing it.
The first step in configuring load distribution is to define a
pool of addresses containing the IP addresses of the real web
servers. Since we are going to take down the original server when
load distribution is complete, its original address of 4.4.4.4 is
going to be a virtual address that is shared by all of the web
servers. To the outside world it will only look like one server
even though each of the servers are sharing part of the load. The
servers still need real IP addresses, and the router needs to know
what those addresses are so that it can send the first request to
the first server, the next address to the next server, etc. Use
the following command:
WebHeads(config)#ip nat pool rot-hosts 4.4.4.10 4.4.4.12
prefix-length 24 type rotary
What does the prefix-length in the previous command refer to?
What does the term rotary mean?
Next we need to define a standard access list permitting the
address of the virtual server(the address that all of the servers will
be sharing).
WebHeads(config)#access-list 5 permit 4.4.4.4
Now is the time to enter the command to establish dynamic inside
destination translation, identifying the access list defined in the
prior step.
WebHeads(config)#ip nat inside destination list 5 pool rot-hosts
Explain in your own words what the previous command is telling the
router.
We next need to tell the router which interface is connected to
inside network and which interface is connected to the outside.
WebHeads(config)#interface fast ethernet 0/0
WebHeads(config-if)#ip nat inside
WebHeads(config)#interface serial 0/0
WebHeads(config-if)#ip nat outside
Now we get to verify the routers address translation.
WebHeads#show ip nat translations
What information did the router respond with?
WebHeads#show ip nat statistics
What information did the router respond with?
For lab testing purposes set the default pages of the 3
different servers to say three different things so you will know which
web server you have hit. Now it is time to test our new configuration.
From a workstation on the ISP routers network open Internet Explorer
or Netscape Navigator. For an IP address, use 4.4.4.4, the IP address
of our virtual server.
WebHeads#show ip nat translations
What information did the router respond with?
WebHeads#show ip nat translations verbose
What additional information did the router respond with?
WebHeads#show ip nat statistics
What information did the router respond with?
From the workstation refresh the Internet browser window a few
times and observe the resulting web pages. Check ip nat translations
again on the router.
What were the inside IP addresses that the NAT table rotated
through?