Lab
9.1.1: Solutions Guide Link
Failure Dial Backup
Objective:
Implement an ISDN dial backup system
for your Frame Relay network between Orlando and Atlanta.
Scenario:
You have just installed an ISDN line
to be used as a dial backup line to your Frame Relay connection
between the Atlanta (hub) and Orlando (stub) office. Configure DDR
on the BRI interface of the Orlando router. Configure Frame Relay on
the serial interfaces connecting to the Frame Relay network. Use
floating static routes to control which link is used.
Lab Tasks:
Cable the lab as shown in the
diagram. Use the Adtran Atlas 550 as your ISDN and Frame Relay networks. Start with a clean config on both routers.
First configure your ISDN BRI
lines. Assign the appropriate SPIDs and dialer maps to implement DDR.
Be sure to configure the following items:
PPP encapsulation
CHAP authentication
ISDN Spid numbers
Idle timeouts
Map statements
Test your DDR configuration to make
sure it is functional.
Next, setup your Frame Relay network. Configure
Frame Relay encapsulation on your serial links.
Use the DLCIs specified in the above diagram.
Use ANSI as your LMI type.
Use sub-interfaces. Configure the
appropriate IP addresses.
Test your Frame Relay configuration
to make sure it is functional
When you are satisfied that both components are functional, turn
on the link down dial backup feature on the Orlando Frame Relay interface. This will enable the BRI line to use DDR when the
Frame Relay link goes down.
For the Orlando router, you need a
default route that prefers the Frame Relay link. If the Frame Relay
link is down, there should be a second default route
that uses the BRI link.
What commands would you use to
install these routes?
For the Atlanta router, you need a
static route to Orlando's Ethernet (192.168.1.0) that first
prefers the Frame Relay link. If the Frame Relay link is down,
there should a second route to that network that uses the BRI
link.
What commands would you use to
install these routes?
At this point, your Frame Relay network should be up. From the
Orlando router, look at your routing table. What is the next hop
address of your default route?
In what state is your BRI interface?
Simulate a link down condition on your
Frame Relay network by
removing the Orlando serial cable to the Frame Relay network. Watch
your console session on the Orlando router to see what happens to
the BRI interface.
What happened?
Did the BRI line dial yet?
Why?
Ping to 192.168.2.1 - What happens?
Look at the routing table on the
Orlando router. What do you notice?
Look at the status of the dial backup
link with the
show backup
command.
Plug the Frame Relay serial link
back in to the Orlando router.
What happens?
While you are waiting for the BRI
line to go back down, check the status of the dial backup link using
the show backup command.
When everything is back to normal, check the status of the dial
backup link using the
show backup
command.