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Point-to-point numbered refers
to connections where the interfaces connecting the
routers to the WAN have IP addresses. On both WAN
ports, the address of the WAN port is set to an IP
address on a common IP network, and the destination
addresses are set to the IP address of WAN port of
the unit on the far side of the link.
====ETHERNET===================== 192.168.1.0/24 ===
|
| LAN Device: Ethernet0
+-------+--------+
| |
| Router A | Bridge IP: 192.168.1.1, 192.168.2.1
| |
+-------+--------+
| WAN Device: Serial0
|
[-] CSU/DSU (may be integrated on WAN card)
|
| PTP WAN
|
[-] CSU/DSU (may be integrated on WAN card)
|
| WAN Device: Serial0
+-------+--------+
| |
| Router B | Bridge IPs: 192.168.1.100, 192.168.2.100
| |
+-------+--------+
| LAN Device: Ethernet0
| LAN Device: Ethernet1
|
|
====ETHERNET===================== 192.168.1.0/24 ===
|
====ETHERNET===================== 192.168.2.0/24 ===
Before You Start
In this network, you will bridge
multiple devices into a single collision domain. It
is possible to bridge multiple WAN devices with any
bridge, including Bonder, MPPP, MLFR, ATM PVCs and Frame
PVCs. Be sure to assign unique IP addresses to all devices
in this network. The bridge operates at OSI model layer
2, and will create a single network from the various
LAN and WAN devices. All devices connected to this bridged
network will have IP addresses from the same network
blocks and common netmasks. The bridge will make the
network appear to be one single, large network.
In the example below, we have inserted bvi16 and bvi5
into the configuration. You may select any bridge group
number and may have as many different bridges as your
configuration requires.
These IP network addresses are given to you by your
Internet Service Provider, your leased line carrier,
or by ARIN. If you do not plan to
connect you network to the Internet, you can use an
IP network address set aside for private use. The IP
network address for private use can be found in RFC
1597. Most people will use 192.168.0.0 as we have in
this example.
Configuring The WAN Ports
In this example, we are going to
assume the following:
- Router A has a LAN network using
the 192.168.1.0/24 netblock and uses the 192.168.1.1
address (and a netmask of 255.255.255.0)
- Router A is the default gateway for
the 192.168.2.0/24 netblock and uses the 192.168.2.1
address (and a netmask of 255.255.255.0)
- Router B has a LAN network using
the 192.168.1.0/24 netblock and uses the 192.168.1.100
address (and a netmask of 255.255.255.0)
- Router B also has a LAN network using
the 192.168.2.0/24 netblock and uses the 192.168.2.100
address (and a netmask of 255.255.255.0) in this
network
- The WAN port on both routers is Serial0.
The IP addresses used in this Technical
Note are examples only, you will need to use an IP network
given to you by your Internet Service Provider.
Router A
!
version 2.00
!
interface Ethernet0
# No IP address used
# The next command adds Ethernet0 to bridge #16
# and disables the use of the spanning-tree algorithm
bridge-group 16 spanning-disabled
!
interface Serial0
description Connection to Router B
encapsulation ppp
# No IP address used
# The next command adds Ethernet0 to bridge #16
# and disables the use of the spanning-tree algorithm
bridge-group 16 spanning-disabled
!
interface bvi16
ip address 192.168.1.1 255.255.255.0
ip address 192.168.2.1 255.255.255.0 secondary
!
end
Router B
!
version 2.00
!
interface Ethernet0
# No IP address used
# The next command adds Ethernet0 to bridge #5
# and disables the use of the spanning-tree algorithm
bridge-group 5 spanning-disabled
!
interface Ethernet1
# No IP address used
# The next command adds Ethernet1 to bridge #5
# and disables the use of the spanning-tree algorithm
bridge-group 5 spanning-disabled
!
interface Serial0
description Connection to Router A
encapsulation ppp
# No IP address used
# The next command adds Ethernet0 to bridge #5
# and disables the use of the spanning-tree algorithm
bridge-group 5 spanning-disabled
!
interface bvi5
ip address 192.168.1.100 255.255.255.0
ip address 192.168.2.100 255.255.255.0 secondary
!
end
Troubleshooting
If the port does not have an "up"
status for both hardware and protocol in the interface
statistics output (Option 2 from the Main menu) do the
following:
If hardware shows "down", check your cable connections
and ensure that you have connected to the correct port.
If you have connected to the correct port, double-check
the telephone company smart jack or other telephone
company-installed equipment for your circuit. The smart
jack should show no red alarms if the cables are connected.
If, after connecting the cables correctly, you have
errors on the telephone company equipment, contact your
line provider for assistance.
If hardware shows "up", but protocol shows "down", you
should see the PPP negotiation and see the status of
the WAN port change to up. At this point you should
be able to ping the other side.
If you have an external CSU/DSU, put the CSU/DSU into
a local loopback. This will cause each packet sent to
the CSU/DSU to reflect back to the WAN port. This is
for testing only, the line will not function while the
CSU/DSU is in a local loopback. If, in the interface
statistics detail output for the port, you see transmitted
packets immediately received on the same port, then
you can determine the following facts:
- The WAN port on the router is sending
and receiving data.
- The cable and connectors between
the router and the CSU/DSU are functioning.
- The DTE port on the CSU/DSU is functioning.
- THE ROUTER IS FUNCTIONING AS IT SHOULD.
If you don't get your packets back
immediately on the same interface:
- For cards with a software-selectable
serial interface, check that you have specified
the correct wiring specification (V.35, RS232, RS422/X.21).
The "dctype" command is typically set to V.35 (the
default) in North America and RS422 in Europe and
Asia.
- That all cables are securely connected.
- Begin swapping hardware, cables,
CSU/DSU, etc.
If you get your packets back immediately,
but the line protocol status is not "up":
- Check the CSU/DSU settings such as
clocking, etc. Almost always the CSU/DSU should
be set for external clocking. Your line provider
typically provides the clock. It's not a bad idea
to verify any external CSU/DSU settings with the
manufacturer.
- Have their telephone carrier test
the line. Requesting a hard copy of the test results
will often get you a better test.
If the line protocol status is "up"
but you can't ping the other side:
- Double check settings. Make sure
that the IP address for the WAN port on both sides
are in the same subnet.
- Do a traceroute from your workstation
through the local (to you) router to the router
in trouble. Then do a traceroute from the router
in trouble (assuming you can get to it) back to
your workstation. The problem will lie in the gap
between the two traceroutes.
- Make sure the default gateway
is set to the upstream router or the serial device
used for the upstream connection, as in our example
above on Router B.
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