![[previous]](../../../graphics/l_arrow.gif){kind=icon}
![[next]](../../../graphics/r_arrow.gif){kind=icon}
This chapter contains information on configuring bridging for the OfficeConnect Remote 840. If you need more information on the difference between Bridging and Routing, and which one is best for your needs, see Appendix A,"Bridging and Routing".
A bridge connects two or more LANs together at Layer 2 (data link) of the ISO-OSI 7 layer model. A learning bridge links networks, but also separates network traffic and forwards only the packets that need to be forwarded based on Media Access Control (MAC) address.
The OfficeConnect Remote 840 can be configured as a learning bridge.
Bridges separate traffic by examining the MAC addresses contained in data packets. MAC addresses uniquely identify each machine attached to a network segment. A data packet is not forwarded to another segment if its destination MAC address resides on the same segment as its source.
To efficiently separate traffic, the bridge maintains a Bridge Forwarding Table. The table contains a list of MAC addresses and their associated network segments. The table is built dynamically from the source MAC addresses of data packets passing through the bridge.
The OfficeConnect Remote 840 bridge supports the Spanning Tree Protocol (STP). This feature is used when two networks are joined by two bridges forming a looped network. STP prevents data packets from circling the two networks.
The OfficeConnect Remote 840 provides a Bridge Firewall function which allows flexible configuration of simultaneous bridging and routing. For more information on the Bridge Firewall, see Appendix A,"Bridging and Routing".
A boot mode, Default Bridge Mode, can be activated. This automatically configures the unit to bridge all packets (see "Default Bridge Mode").
For more information on bridging, see Appendix A, "Bridging and Routing".
To set up bridging on the OfficeConnect Remote 840, you must:
You may also want to:
If you are planning to use the OfficeConnect Remote 840 to bridge all traffic, you may want to use the boot option Default Bridge Mode (see "Default Bridge Mode").
To configure a protocol over the LAN, you need to assign a protocol network to the LAN port by providing a name. After adding a network, you can modify advanced parameters. The network's status appears in the Monitor > Networks > Network Status table.
For bridging to take place across the OfficeConnect Remote 840, you also have to enable bridging over the WAN port. See "Configuring Bridging for the Remote Site Connections".
Use the Local Site (LAN) > Bridge Configuration screen to define or modify a bridged network over the LAN.
Only one bridged network can be added over the LAN.
You may add a bridged network over the Ethernet interface by following these steps:
1 . Select Configuration > Local Site (LAN) > Bridge.
2 . Click Add. This accesses a screen containing the following fields.
3 . Enter the following:
4 . Check the Enable Bridge box and click Add when the name has been entered to save your field.
5 . Check the Enable Spanning Tree box if you wish to enable spanning tree, which is used to eliminate loops in a circular bridged network.
To modify information pertaining to an existing Bridge network, or to delete that information from your configuration, follow these steps:
1 . Proceed to the Bridge screen, following steps 1 and 2 above.
2 . Select the bridge network you wish to modify or delete.
3 . Click Modify/Delete. This accesses a screen containing the following fields:
4 . You may uncheck the Enable Bridge or Enable Spanning Tree boxes if you have previously checked them from this screen, or delete the information about the selected Bridge network by clicking Delete.
5 . To alter previously set fields, follow step 1 and select a Bridge network in the list and click Modify. To delete a network from your configuration, select a network and click Delete.
6 . Click Modify after you have entered the field.
To set up a protocol over the WAN, a remote site profile must be created and edited for each remote location you want to connect to. With this profile, you specify virtual circuit (VPI, VCI) information, protocols, and addresses that determine the method of connection and communication to that remote site.
The steps you take to assign a network over the WAN are quite different from those to assign a network over the LAN. First you add a remote site profile, and then you modify the profile to enable bridging.
When the remote site connection is established, the bridge network will come up over the WAN interface. The network and its status appears in the Monitor > Network > Network Status table.
If you need to connect to multiple remote sites, such as two remote offices, set up a remote site profile for each remote location.
For any routing to take place across the OfficeConnect Remote 840, you also have to set up a corresponding network over the LAN. See "Configuring Bridging for the LAN".
These instructions assume you have already added a remote site profile. If you have not added one, select Add instead of Modify in step 1 and see "Remote Site Management" for details on other parameters to configure.
To enable bridging:
1 . From the OfficeConnect Remote 840 home page, select Configuration > Remote Sites (WAN), select a remote site definition, and click Modify. This accesses the Remote Sites General Modify screen, containing the following fields:
2 . Check the Enable Bridging box to enable bridging for this remote site. Then click Modify.
Unless you are using the boot option Default Bridge Mode, the OfficeConnect Remote 840 is set up to route IP traffic by default. To bridge IP traffic, you must turn off IP Forwarding in the router configuration.
IP Forwarding refers to the routing of IP packets from one interface to another. It does not affect communicating to the OfficeConnect Remote 840 itself. Even when IP Forwarding is disabled, you can perform non-routing functions such as use the OfficeConnect Remote 840 Manager from a Web browser and use PING.
To bridge IP traffic:
1 . Add the bridge network over the LAN (see the instructions above).
2 . From the OfficeConnect Remote 840 home page, select Configuration > Global > IP > IP Settings. This brings up the IP Settings screen:
3 . Turn off IP forwarding by unchecking the Forwarding check box.
4 . Your browser will temporarily lose connection with the OfficeConnect Remote 840. Wait a few seconds, click the browser's Stop button; then click Reload.
Because routers base their forwarding decision on network-level addresses, packets that are routed over a WAN are transmitted without MAC-layer addresses. Additionally, address resolution procedures that can be used to determine the destination MAC address for a packet are not required.
Conversely, packets that are bridged over a Wide Area Connection include MAC-layer information. Address resolution procedures are required.
MAC-Encapsulated Routing uses network-level addresses for forwarding decisions but transmits MAC-layer addresses over the Wide Area Connection. Additionally, address resolution procedures are used. To the remote site, the packets appear as if they had been bridged.
This feature allows the routing features of the OfficeConnect Remote 840 (i.e., address translation, DHCP Server, DNS Proxy, etc.) to be employed in a bridged environment.
MAC-Encapsulated Routing is specified on a remote site basis. When MAC-Encapsulated Routing is enabled in a remote site profile, packets for the routed protocols configured by the profile (i.e., IP and/or IPX) will be sent using the appropriate bridged encapsulation. If the configured Network Service is PPP, the packets will be encapsulated in BRCP.
MAC-Encapsulated Routing is configured on the Remote Sites General screen.
To access the Remote Sites General screen:
1 . Go to the OfficeConnect Remote 840 home page and select Configuration > Remote Sites (WAN).
2 . Select a defined remote site and click Modify. This will access the Remote Sites General Modify screen, containing the following fields:
3 . Check the Enable MAC Encapsulated Routing box to enable MAC Encapsulated Routing for this remote site.
4 . Click Modify to save the change.
The OfficeConnect Remote 840 can be configured for simultaneous bridging and routing. IP routing is configured if IP forwarding is enabled (see "Enabling IP Routing" in Chapter 4.)
IPX routing is enabled if an IPX network is present over the Ethernet interface (see "Configuring IPX for the LAN" in Chapter 9). Bridging is enabled by adding a bridge network over the Ethernet interface (see "Configuring Bridging for the LAN"). Routing and bridging are enabled for each destination in its remote site profile.
When configured for simultaneous bridging and routing, packets received from the LAN are first passed through the router for any configured protocols. If the packet can not be routed, it is passed to the bridge depending on the setting of the Bridge Firewall function. The bridge firewall has three modes, which are configured on the Advanced Bridging Options screen.
The three modes are:
1. Discard Routed Protocols (Discard):
This is the default mode. If a protocol is configured for routing, and a packet for that protocol type is received from the LAN that is not addressed to the MAC address of the OfficeConnect Remote 840, it is discarded. Additionally, broadcasts (including ARPs) for the protocol are not passed to the bridge.
2. Forward Unicast Packets Only (Unicast):
If a protocol is configured for routing, and a packet for that protocol type is received from the LAN that is not addressed to the MAC address of the OfficeConnect Remote 840, it is bridged. Additionally, ARP broadcasts for IP addresses other than that of the OfficeConnect Remote 840 are also bridged. Other broadcasts for the configured protocol are not bridged.
3. Forward Broadcast/Unicast Packets (All):
Unicast packets for a configured protocol received from the LAN that are not addressed to the MAC address of the OfficeConnect Remote 840 are bridged. Received broadcasts (e.g., DHCP) are bridged.
Packets received from the WAN do not pass through the Bridge Firewall. Instead, packets received from the WAN are delivered to the router or they are delivered to the router or bridging function based on their encapsulation and on the state of the MAC-Encapsulated Routing parameter in the remote site profile.
In general, a packet received in a routed encapsulation (i.e., IPCP or routed RFC 1483 or RFC 1490) is delivered to the router. A packet received in a bridged encapsulation is passed to the bridge. If MAC-Encapsulated Routing is enabled, the received (bridge-encapsulated) packets are delivered to the router.
The advanced bridging configuration options are located with the rest of the Local Site configuration options. However, these advanced bridging options function more as global parameters and therefore are applicable to bridging over the WAN as well as the LAN.
Most users do not need to change these values from the defaults.
To alter advanced bridging configurations:
1 . Go to the OfficeConnect Remote 840 home page and select Configuration > Local Site > Bridge.
2 . Click Advanced to access a screen containing the following field:
If you need to return to the original parameters for this screen, click Reset before you click Submit.
3 . Click Submit when the fields have been entered to save your customizations.
Default Bridge Mode is designed for those who want to use their OfficeConnect Remote 840 to function as a bridge automatically, with no special configuration or software installation required. This mode preconfigures the unit to bridge all packets.
In this mode, you will not be required to use Setup Wizard or install any software from the CD unless you want to change the configuration (you can install from the CD at any time).
There are several different settings for Default Bridge Mode. The different settings control the WAN operational mode; ATM or Frame Relay, and the VPI/VCI or DLCI settings.
If you set the OfficeConnect Remote 840 to this mode and no configuration exists, the OfficeConnect Remote 840 will automatically set up a bridge network on the Ethernet and will create a VC profile that bridges using RFC 1483 or RFC 1490 encapsulation with various VPI/VCI or DLCI values (see "DIP Switch Modes" table in Chapter 1 for details on how to set your router switches to obtain the correct VPI/VCI values for your configuration).
Your OfficeConnect Remote 840 was set in Unconfigured Mode (all switches OFF) before shipping.
The following settings are preconfigured:
You will need to tell your service provider to use a connection on VPI / VCI using RFC 1483 or RFC 1490 (bridged).
Boot options only affect the operation of a unit which does not presently have any configuration settings (i.e., the unit is new, the reset button has been clicked, or a delete configuration command has been executed from the CLI or HTML interface). See "Restoring Factory Defaults" in Chapter 2 for more information on how to reset configuration parameters for your OfficeConnect Remote 840.
For more instructions on setting up your OfficeConnect Remote 840 using Default Bridge Mode, see the OfficeConnect Remote 840 SDSL Router Install Guide that was included the box when you purchased your SDSL router.
You can view bridge network status from the Monitor > Networks > Network Status screen. This lists the networks (WAN networks incorporate the word "port" in the name) and shows you their states.
The Bridge Forwarding Table is displayed in the Monitor > Routes and Services > Bridge Forwarding screen. In addition to listing the MAC addresses, it provides counters for traffic passing through the bridge to and from the addresses.
General bridge transmit and receive counters are located in the Monitor > Networks > Bridge screen.
To test bridging:
If you have problems with bridging IP, check that IP Forwarding is disabled on the Configuration > Global > IP > IP Settings screen. Also, be sure that your LAN IP Addresses belong to the same IP network as the remote site.