Testing Tips

Bridge mode testing with CDRouter

7 min read

CDRouter includes support for testing basic Layer 2 bridging devices including wireless access points, broadband access devices, and Ethernet switches. CDRouter can be used to verify the following functionality of a DUT operating in bridge mode:

  • IPv4 and IPv6 forwarding
  • TR-069 client
  • 802.1x port based authentication
  • VLAN functionality

Basic Configuration

To enable bridge mode within CDRouter, set the testvar forwardingMode to bridge. This testvar supports two values, route for routing devices or bridge for Layer 2 bridging devices. The default value is route.

For bridging devices, the wanMode and ipv6WanMode testvars are still used to determine how the DUT obtains its IPv4 and IPv6 management addresses, respectively, if applicable.

In most scenarios, the DUT’s DHCP server will be disabled when configured for bridge mode. As a result, CDRouter will automatically enable its internal DHCP server on the LAN when bridge mode is used. This allows CDRouter’s LAN client to obtain an IPv4 address and DNS information. CDRouter’s internal DHCP server will assign addresses from the configured DHCP pool and provide the DNS server address specified by the testvar internalDHCPdns:

testvar dhcpClientStart       192.168.1.2
testvar dhcpClientEnd         192.168.1.7
testvar internalDHCPdns       1.1.1.1

Likewise, if IPv6 is enabled, CDRouter will also send router advertisements on the WAN that should be bridged to the LAN so that its LAN IPv6 client can obtain an address. The router advertisements will contain the prefix information specified by the following testvars:

testvar ipv6WanIspIp             3001::1
testvar ipv6WanIspPrefixLen      64

Note that CDRouter can be used to test TR-069, if supported by the DUT in bridge mode. When configured for bridge mode, CDRouter will also automatically skip any test cases or test modules that are not applicable or incompatible.

Typically, a DUT in bridge mode will obtain an IP address for its management interface using one of the following methods:

  • IPv4: DHCP or static configuration
  • IPv6: DHCP, autoconf, or static configuration

Likewise, CDRouter supports all of the above WAN modes for bridge mode configurations. In addition, CDRouter also supports a new IPv6 WAN mode of none. This new IPv6 WAN mode is useful for testing IPv6 forwarding on devices that do not support IPv6 directly on their management interface.

testvar ipv6WanMode none

Examples

There are three common Layer 2 bridging scenarios that can be tested and verified with CDRouter:

  • 802.11 a/b/g/n wireless access points
  • Broadband CPE in bridge mode (DSL, DOCSIS, or PON)
  • Ethernet switches

CDRouter can also be used to verify the DUT’s TR-069 client functionality, if present. Configuration examples for each scenario are provided below.

Configuration Example 1: An 802.11 a/b/g/n wireless access point

Wireless access points typically have a single Ethernet interface which is connected to another switch or gateway. The access point then provides network connectivity to clients connected via 802.11 a/b/g/n.

The CDRouter test setup for this example is shown below:

bridge_AP[1]

In this example the DUT is an 802.11 a/b/g/n wireless access point. CDRouter’s WAN interface (eth1) is directly connected via Ethernet to the DUT’s WAN/Ethernet port. Likewise, CDRouter’s LAN interface (wlan0) will associate and connect to the DUT’s 802.11 a/b/g/n network. A simple CDRouter configuration based on the following assumptions is provided below.

  • Management interface IPv4 address: static, 192.168.1.50
  • Management interface IPv6 address: not supported
  • Wireless mode: 802.11g
  • Wireless security: none (basic wireless)*
  • TR-069 support: no

NOTE: CDRouter supports a wide range of wireless security schemes. Please see this Knowledge Base article for more information.


# Enable forwarding mode within CDRouter
testvar forwardingMode        bridge

# LAN IPv4 configuration
testvar lanInterface          wlan0
testvar lanType               802.11g
testvar lanSSID               bridge_AP
testvar lanWepKey             off
testvar dhcpClientStart       192.168.1.2
testvar dhcpClientEnd         192.168.1.7

# WAN IPv4 configuration
testvar wanInterface          eth1
testvar wanMode               static
testvar wanIspIp              192.168.1.10
testvar wanIspAssignIp        192.168.1.50

# IPv6 configuration
testvar supportsIPv6          yes
testvar ipv6WanMode           none
testvar ipv6WanIspIp          3001::1
testvar ipv6WanIspPrefixLen   64

In this example CDRouter will automatically enable its internal DHCP server using the address range specified by the testvars dhcpClientStart and dhcpClientEnd. Once associated with the DUT, CDRouter’s LAN client will obtain an IPv4 address from within this range. In addition, CDRouter will send NDP Router Advertisements on the WAN based on the address and prefix length specified by the testvars ipv6WanIspIp and ipv6WanIspPrefixLen, respectively. These Router Advertisements will be forwarded by the access point to all associated clients thereby allowing CDRouter’s LAN client to obtain an IPv6 address as well.

Configuration Example 2: A DSL CPE in bridge mode

Many broadband access devices, including DSL CPE, DOCSIS gateways, and PON ONUs, can be optionally configured in bridge mode. In bridge mode the access device simply provides connectivity between the service provider’s DSL, DOCSIS, or PON network and the customer premise. A traditional Ethernet-to-Ethernet gateway is then typically connected to the LAN side of the bridged access device.

The CDRouter test setup for this example is shown below:

bridge_DSL[1]

In this example the DUT is assumed to be a DSL CPE in bridge mode, but this same topology is applicable to other broadband access technologies such as DOCSIS and PON as well. CDRouter’s WAN interface (eth1) is directly connected to the DSLAM via Ethernet. Likewise, CDRouter’s LAN interface (eth2) is connected via Ethernet to the LAN side of the DUT. A simple CDRouter configuration based on the following assumptions is provided below.

  • Management interface IPv4 address: DHCP
  • Management interface IPv6 address: DHCPv6
  • Wireless mode: not supported
  • Wireless security: not supported
  • TR-069 support: yes

# Enable forwarding mode within CDRouter
testvar forwardingMode        bridge

# LAN IPv4 configuration
testvar lanInterface          eth2
testvar lanType               ethernet
testvar dhcpClientStart       192.168.1.2
testvar dhcpClientEnd         192.168.1.7

# WAN IPv4 configuration
testvar wanInterface          eth1
testvar wanMode               DHCP
testvar wanIspIp              192.168.1.1
testvar wanIspAssignIp        192.168.1.50

# IPv6 configuration
testvar supportsIPv6          yes
testvar ipv6WanMode           DHCP
testvar ipv6WanIspIp          3001::1
testvar ipv6WanIspAssignIp    3001::2
testvar ipv6WanIspPrefixLen   64

# TR-069 configuration
testvar acsIp                 6.0.0.1
testvar acsPort               80
testvar acsTransport          http
testvar acsAuth               digest

# CDRouter default values used for remainder of TR-069 configuration

Configuration Example 3: Ethernet switch with 802.1x port based authentication

CDRouter’s support for bridge mode makes it possible to test basic Ethernet switching devices, including those that implement 802.1x for port based authentication. A detailed discussion of testing 802.1x enabled devices with CDRouter can be found here. Although this testing guide is specific to 802.1x in gateway devices, many of the principles are applicable to devices operating in bridge mode as well.

The CDRouter test setup for this example is shown below:

bridge_Switch[1]

In the example below the DUT is a managed 8-port Ethernet switch that has ports 1 and 8 in a separate VLAN. Port 8 on the switch is configured with VLAN ID 100 (tagged) and 802.1x port based authentication. Port 8 is connected to CDRouter’s LAN (eth2) while port 1 (also tagged with VLAN 100) is connected to CDRouter’s WAN (eth1). Using this setup CDRouter is capable of testing not only the basic forwarding functionality the DUT, but also the DUT’s 802.1x authenticator functionality. A simple CDRouter configuration based on the following assumptions is provided below.

  • Management interface IPv4 address: DHCP
  • Management interface IPv6 address: DHCPv6
  • Wireless mode: not supported
  • Wireless security: not supported
  • TR-069 support: no
  • 802.1x support: yes, port 8
  • VLANs: yes, ports 1 and 8 tagged with VLAN ID 100

# Enable forwarding mode within CDRouter
testvar forwardingMode        bridge

# LAN IPv4 configuration
testvar lanInterface          eth2
testvar lanType               ethernet
testvar dhcpClientStart       192.168.1.2
testvar dhcpClientEnd         192.168.1.7

# VLAN configuration
testvar lanVlanId             100
testvar lanVlanPriority       1
testvar wanVlanId             100
testvar wanVlanPriority       1

# WAN IPv4 configuration
testvar wanInterface          eth1
testvar wanMode               DHCP
testvar wanIspIp              192.168.1.1
testvar wanIspAssignIp        192.168.1.50

# IPv6 configuration
testvar supportsIPv6          yes
testvar ipv6WanMode           DHCP
testvar ipv6WanIspIp          3001::1
testvar ipv6WanIspAssignIp    3001::2
testvar ipv6WanIspPrefixLen   64

# 802.1x configuration
testvar wanRadiusEnable       yes
testvar wanRadiusIp           3.3.3.44
testvar wanRadiusSecret       qacafe123
# See Application Note on 802.1x testing for more information
# on the configuration EAP identities

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