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The Asynchronous Transfer Mode (ATM) Cable Interface Processor (ACIP) is available on Cisco 7500 series routers. The ACIP provides a single, full-duplex ATM network interface for connection to a cable facilitiy's headend at data rates up to 155 Mbps bidirectionally. The ACIP has one multimode duplex SC connector or two single SC connectors that support SONET/SDH multimode fiber optic cable (STS-3C or STM-1).
The ACIP supports the following features:
Perform the tasks in the following sections to configure the ACIP interface (all tasks are required except for the last task):
After you configure the ACIP, you must configure the cable headend and/or ATM switch.
For information on other commands that can be used by the ACIP such as bridging, refer to the Cisco IOS Release 11.2 configuration guides.
For ACIP configuration examples, see the "Configuration Example" section later in this chapter.
The ACIP interface (or subinterface) uses the configuration defaults shown in Table 41. For information on how to change the defaults, refer to the "Configuring ATM" chapter of the Wide-Area Networking Configuration Guide and the "Configuring Interfaces" chapter of the Configuration Fundamentals Configuration Guide. All ATM and interface commands might not be applicable to the ACIP interface. If a command is not available, the router displays the message "Command not supported on this interface."
| Parameter | Command | Default Value |
|---|---|---|
| Maximum transmission unit | mtu bytes | 4470 |
| Exception queue buffers | atm exception queue number | 32 |
| Receive buffers | atm rxbuff number | 256 |
| Transmit buffers | atm txbuff number | 256 |
| Maximum number of virtual circuits (VCs) | atm maxvc number | 2048 |
| ATM raw cell queue size | atm rawq-size number | 32 |
| ATM VCs per VP | atm vc-per-vp number | 1024 |
| Source of Transmit Clock | atm clock internal | Recovered receive clock |
To configure the ATM interface on the ACIP, perform the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
| Step 1 Assign a bridge group.1 | bridge bridge-group protocol {dec | ieee} |
| Step 2 Specify the interface and enter interface configuration mode. | interface atm slot/0 |
| Step 3 Assign the bridge group to the interface. | bridge-group number |
| Step 4 Disable the spanning tree on the interface. | bridge-group number spanning-disabled |
| Step 5 Change the shutdown state to up and enable the interface. | no shutdown |
To assign the ATM interface on the ACIP to a cable headend and specify the cable headend IP address, perform the following tasks beginning in global configuration mode:
After you have set up the interfaces in the router, you can enable integrated routing and bridging.
To enable integrated routing and bridging, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Enable integrated routing and bridging. | bridge irb |
Use the show interfaces irb privileged EXEC command to display the protocols that a given bridged interface can route to the other routed interface when the packet is routable, and to display the protocols that a given bridged interface bridges.
The bridge-group virtual interface resides in the router. It acts like a normal routed interface that does not support bridging, but represents the entire corresponding bridge group to routed interfaces within the router. The bridge-group virtual interface is assigned the number of the bridge group that it represents. The bridge-group virtual interface number is the link between the bridge-group virtual interface and its bridge group. Because the bridge-group virtual interface is a virtual routed interface, it has all the network layer attributes, such as a network address and the ability to perform filtering. Only one bridge-group virtual interface is supported for each bridge group.
When you enable routing for a given protocol on the bridge-group virtual interface, packets coming from a routed interface but destined for a host in a bridged domain are routed to the bridge-group virtual interface, and are forwarded to the corresponding bridged interface. All traffic routed to the bridge-group virtual interface is forwarded to the corresponding bridge group as bridged traffic. All routable traffic received on a bridged interface is routed to other routed interfaces as if it is coming directly from the bridge-group virtual interface.
To create a bridge-group virtual interface, perform the following tasks in interface configuration mode:
When integrated routing and bridging is enabled, the default route/bridge behavior in a bridge group is to bridge all packets.
You could then explicitly configure the bridge group to route a particular protocol, so that routable packets of this protocol are routed, while non-routable packets of this protocol or packets for protocols for which the bridge group is not explicitly configured to route will be bridged.
To configure specific protocols to be routed in a bridge group, perform the following task in global configuration mode:
| Task | Command |
|---|---|
| Specify the IP protocol to be routed in a bridge group. | bridge bridge-group route ip |
When you intend to bridge and route a given protocol in the same bridge group, you must configure the network-layer attributes of the protocol on the bridge-group virtual interface. Do not configure protocol attributes on the bridged interfaces. No bridging attributes can be configured on the bridge-group virtual interface.
Although it is generally the case that all bridged segments belonging to a bridge group are represented as a single segment or network to the routing protocol, there are situations where several individual networks coexist within the same bridged segment. To make it possible for the routed domain to learn about the other networks behind the bridge-group virtual interface, configure a secondary address on the bridge-group virtual interface to add the corresponding network to the routing process.
After configuring the new interface, you can display its status. You can also display the current status of connections and active modems on each interface. To show current status information, perform any of the following tasks in EXEC mode:
The following example shows how to configure the ACIP interface; it also shows other Cisco IOS commands required for the ACIP to connect to a cable headend (modem).
Each ATM virtual circuit carries data for a single subscriber cable data modem. Data sent over this interface is first encapsulated in Ethernet frames and then encapsulated in AAL5 CPCS-PDU (per RFC 1483 LLC SNAP Encapsulation of Bridged Protocols). To support encapsulation, the router must operate as an integrated router/bridge by using the bridge irb command and the bridge-group virtual interface (interface bvi command). The bridge-group virtual interface decapsulates the Ethernet packets received from the ATM interface and multiplexes the router interface to multiple virtual circuits (VCs). No actual bridging is performed between VCs.
All of the IP devices on each of the Ethernet interfaces of the subscriber cable data modem must be on the same IP subnet. The router, in general, will not perform an ARP to find MAC addresses of hosts, instead the router will assume that DHCP is used by each host. Because entries in the ARP table must not age out normally, the software automatically adds the bridge number aging-time 604800 command to the configuration file.
Data from one host to another on the same cable channel must be sent via the router. The router knows that two hosts are both on the same subnet and would normally send an ICMP redirect to inform the first host that a better path exists. However, because the cable media does not support direct host-to-host communications, the router must do the forwarding, and the ICMP must be suppressed with the no ip redirects command.
The cable bind command specifies the headend IP address (1.1.1.2), and the BVI interface specifies the local IP address (1.1.1.1).
router(config)#interface atm 5/0router(config-if)#bridge-group 1router(config-if)#bridge-group 1 spanning-disablerouter(config-if)#no shutdownrouter(config-if)#exitrouter(config)#cable bind atm 5/0 17 1.1.1.2router(config)#bridge irbrouter(config)#interface bvi 1router(config-if)#ip address 1.1.1.1 255.255.255.0router(config-if)#no ip redirectsrouter(config-if)#exitrouter(config)#bridge 1 protocol decrouter(config)#bridge 1 route iprouter(config)#exit
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 11.2 command references.
To assign the ATM interface on the ACIP to a cable headend modem, use the cable bind global configuration command. To disable this feature, use the no form of this command.
cable bind atm-interface vpi ip-address| atm-interface | ATM interface handling the data traffic to the subscriber cable data modem. |
| vpi | ATM network virtual path identifier (VPI) of this virtual circuit. The value ranges from 0 through 255.
The VPI is an 8-bit field in the header of the ATM cell. The VPI value is unique only on a single link, not throughout the ATM network because it has local significance only. The VPI value must match that of the switch. |
| ip-address | IP address of the cable headend modem. |
Disabled
Global configuration
This command first appeared in Cisco IOS Release 11.2 P.
The following example assigns the ATM interface 3/0 to the cable headend modem at the IP address 1.1.1.1:
cable bind atm 3/0 17 1.1.1.1
To enable proxy-Address Resolution Protocol (ARP) handling when user-to-user communication is permitted for each data modem channel, use the cable enable-proxy global configuration command. To disable this feature, use the no form of this command.
cable enable-proxy atm-interface vpi| atm-interface | ATM interface handling the data traffic to the subscriber cable data modem. |
| vpi | ATM network virtual path identifier (VPI) of this virtual circuit. This value ranges from 0 through 255.
The VPI is an 8-bit field in the header of the ATM cell. The VPI value is unique only on a single link, not throughout the ATM network because it has local significance only. The VPI value must match that of the switch. |
Disabled
Global configuration
This command first appeared in Cisco IOS Release 11.2 P.
If a host sends an ARP request for another host on the same subnet, the router can use its proxy ARP capability to answer the request.
The following example enables proxy-ARP on ATM interface 3/0:
cable enable-proxy atm 3/0 17
To display the status of active channels, use the show cable channels EXEC command. A channel is a single downstream/upstream connection on the headend modem (the same as a TV channel).
show cable channelsThis command has no arguments or keywords.
EXEC
This command first appeared in Cisco IOS Release 11.2 P.
The following is sample output from the show cable channel command:
router# show cable channel
State BVI Interface VPI Speed(kbps) Vendor IP Address
up BVI1 ATM5/0.1 17 8192 Terayon 16.5.121.6
Table 42 describes the fields shown in the display.
| Field | Description |
|---|---|
| State | State of this virtual circuit. Values are:
|
|
BVI | Bridged-virtual interface associated with the ATM interface. |
| Interface | Interface type and slot. |
| VPI | ATM network virtual path identifier (VPI) of this virtual circuit. This value ranges from 0 through 255. |
| Speed | Speed of the downstream connection in kbps. |
| Vendor | Cable headend modem vendor name. |
| IP Address | IP address of the cable headend modem associated with the ATM interface. |
To display the status of active subscriber modems, use the show cable modem EXEC command.
show cable modemThis command has no arguments or keywords.
EXEC
This command first appeared in Cisco IOS Release 11.2 P.
The following is sample output from the show cable modem command:
router# show cable modem
Interface VCD VPI VCI Modem ID
ATM5/0.1 1381 17 32 0202.0202.0300
ATM5/0.1 1382 17 33 0202.0202.0301
Table 43 describes the fields shown in the display.
| Field | Description |
|---|---|
| Interface | Interface type and slot. |
| VCD | Virtual circuit descriptor (VCD) of this virtual circuit. The value ranges from 1 to the value set with the atm maxvc command. |
| VPI | Virtual path identifier (VPI) of this virtual circuit. The value ranges from 0 through 255. |
| VCI | Virtual circuit identifier (VCI) of this virtual circuit. The value ranges from 0 through 65535. |
| Modem ID | Identification of the subscriber modem (MAC address). |
This section describes the debug commands that can be used to troubleshoot the ACIP.
To display changes in connectivity to the cable headend modem, use the debug cable channel EXEC command.
[no] debug cable channelThe debug cable channel command shows status changes on configured cable channels.
Figure 17 shows sample debug cable channel output. In this example, the channel state changes from down to up. Use the show cable channel command to verify the status.
router# debug cable channel
%CDM-6-CHANNELDOWN: Channel(vpi=17) on ATM5/0.1, changed state to down
%CDM-6-CHANNELUP: Channel(vpi=17) on ATM5/0.1, changed state to up
To display changes in the subscriber modem status, use the debug cable modem EXEC command.
[no] debug cable modemThe debug cable modem command shows status changes on the subscriber modems.
Figure 18 shows sample debug cable modem output. In this example, the modem state changes from down to up. Use the show cable modem command to verify the status.
router# debug cable modem
%CDM-6-MODEMDOWN: Modem(vci=32) on ATM5/0.1, changed state to down
%CDM-6-MODEMDOWN: Modem(vci=33) on ATM5/0.1, changed state to down
and
%CDM-6-MODEMUP: Modem(vci=32) on ATM5/0.1, changed state to up
%CDM-6-MODEMUP: Modem(vci=33) on ATM5/0.1, changed state to up
To display error messages caused by unexpected system behavior or problems connecting to the cable headend modem, use the debug cable error EXEC command.
[no] debug cable errorThe debug cable error command shows internal errors messages. These messages indicate internal errors or errors in the connection to the cable headend.
Figure 19 shows all possible messages you can receive when you use the debug cable error command. If you receive any of these messages, copy the message exactly as it appears, and report it to your technical support representative.
cable: Internal error (1) [ to (15) ] cable: Cannot send packet to <IP-Address>. cable: authentication error reading from <IP-Address>. cable: parse error reading from <IP-Address>. cable: No response from <IP-Address>. cable: Unrecognized return data type <Value>. cable: channel not configured cable: cdm_snmp_set_req() failure
For more information on the ACIP, refer to the ATM Cable Interface Processor (ACIP) Installation and Configuration publication.
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