Installation guide

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Cisco uBR7100 Series Universal Broadband Router Software Configuration Guide
OL-2238-03
Chapter 4 Configuring Basic Broadband Internet Access
Transparent Bridging Configuration
Transparent Bridging Configuration
Bridging operation between the cable interface and port adapter interfaces is typically not used in
DOCSIS CMTS installations because of potential performance and security problems, but bridging
operations is appropriate for certain MDU/MTU applications. For example, a hotel could offer Internet
connectivity for customers who want to use a fixed IP address, as opposed to being assigned a temporary
IP address from the local server’s DHCP address pool.
Note Transparent bridging is supported only when using Cisco IOS Release 12.1(7)EC or greater. For
complete details on transparent bridging and IRB operation, see the Bridging chapters in the Cisco IOS
Bridging and IBM Networking Configuration Guide, Release 12.1, available on CCO and the
Documentation CD-ROM.
The following sample configuration file configures the Cisco uBR7111 router for basic bridging
operation with the following features:
• Basic DOCSIS Internet Access using bridging operations—This requires the following:
– IP routing is disabled.
– The FastEthernet and cable interfaces are assigned to the same bridge group.
– Each interface receives the same IP address since they form one logical network.
– The subscriber-loop-control bridging option is enabled on the cable interface to allow packets
received on an upstream to be forwarded to another cable modem host on the downstream.
Note The spanning-tree protocol is disabled, by default, on the cable interface, but this is not
required.
• DOCSIS Cable Modem Configuration Files—These configuration files provide several different
service level options:
– platinum.cm—Users are given a maximum upstream bandwidth of 128kbps, with a guaranteed
minimum bandwidth of 10kbps. The downstream has a maximum bandwidth of 10Mbps. Up to
8 PCs are allowed on this connection.
– gold.cm—Users are given a maximum upstream bandwidth of 64kbps and a maximum
downstream bandwidth of 5Mbps. Up to 3 PCs are allowed on this connection.
– silver.cm—Users are given a maximum upstream bandwidth of 64kbps and a maximum
downstream bandwidth of 1Mbps. Only 1 PC is allowed on this connection.
– disable.cm—Users are denied access to the cable network. This configuration file can be used
for users who have cancelled service or have not paid their bills.
• TFTP server provides access to the cable modem configuration files (but a DHCP server is not
supported in bridging mode)
The following is a typical configuration file for transparent bridging operation:
!
version 12.1
no service pad
service timestamps debug datetime msec localtime
service timestamps log datetime
no service password-encryption
service udp-small-servers max-servers no-limit
service tcp-small-servers max-servers no-limit