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Use the commands described in this chapter to configure access to Frame Relay networks.
For Frame Relay configuration information and examples, refer to the "Configuring Frame Relay" chapter in the Router Products Configuration Guide.
To clear dynamically created Frame Relay maps, which are created by the use of Inverse ARP, use the clear frame-relay-inarp EXEC command.
This command has no arguments or keywords.
The following example clears dynamically created Frame Relay maps:
frame-relay inverse-arp
show frame-relay map
To enable Frame Relay encapsulation, use the encapsulation frame-relay interface configuration command. To disable Frame Relay encapsulation, use the no form of this command.
Use this command with no keywords to restore the default Cisco encapsulation.
The following example configures Cisco Frame Relay encapsulation on interface serial 1:
Use the ietf keyword if your router is connected to another vendor's equipment across a Frame Relay network to conform with RFC 1490:
To create a special queue for a specified interface to hold broadcast traffic that has been replicated for transmission on multiple DLCIs, use the frame-relay broadcast-queue interface configuration command.
The default values are as follows:
size—64 packets
byte-rate—256000 bytes per second
packet-rate—36 packets per second
For purposes of the Frame Relay broadcast queue, broadcast traffic is defined as packets that have been replicated for transmission on multiple DLCIs, but it does not include the original routing packet or SAP packet, which passes through the normal queue. Due to timing sensitivity, bridged broadcasts and spanning tree packets are sent through the normal queue.
The Frame Relay broadcast queue is managed independently of the normal interface queue. It has its own buffers and a configurable service rate.
A broadcast queue is given a maximum transmission rate (throughput) limit measured in bytes per second and packets per second. The queue is serviced to ensure that only this maximum is provided. The broadcast queue has priority when transmitting at a rate below the configured maximum, and hence has a guaranteed minimum bandwidth allocation. The two transmission rate limits are intended to avoid flooding the interface with broadcasts. The actual limit in any second is the first rate limit that is reached.
Given the transmission rate restriction, additional buffering will be required to store broadcast packets. The broadcast queue is configurable to store large numbers of broadcast packets.
The queue size should be set to avoid loss of broadcast routing update packets. The exact size will depend on the protocol being used and the number of packets required for each update. To be safe, set the queue size so that one complete routing update from each protocol and for each DLCI can be stored. As a general rule, start with 20 packets per DLCI.
As a general rule, the byte rate should be less than both of the following:
The packet rate is not critical if you set the byte rate conservatively. As a general rule, set the packet rate assuming 250-byte packets.
The following example specifies a broadcast queue to hold 80 packets, to have a maximum byte transmission rate of 240,000 bytes per second, and to have a maximum packet transmission rate of 160 packets per second:
To specify the discard eligibility (DE) group number to be used for a specified DLCI, use the frame-relay de-group interface configuration command. To disable a previously defined group number assigned to a specified DLCI, use the no form of the command with the relevant keyword and arguments.
To disable all previously defined group numbers, use the no form of this command with no arguments.
This command requires that Frame Relay software be enabled.
The DE bit is not set or recognized by the Frame Relay switching code, but must be recognized and interpreted by the Frame Relay network.
The following example specifies that group number 3 will be used for DLCI 170:
To define a discard eligibility (DE) list specifying which packets will have the DE bit set and thus will be eligible for discarding when congestion is experienced on the Frame Relay switch, use the frame-relay de-list global configuration command. To delete a portion of a previously defined DE list, use the no form of this command.
Discard eligibility is not defined.
To remove an entire DE list, use the no form of this command with no options and arguments.
This prioritization feature requires that the Frame Relay network be able to interpret the DE bit as indicating which packets can be dropped first in case of congestion or which packets are less time sensitive or both.
The following example specifies that IP packets larger than 512 bytes will have the discard eligibility bit set.
To assign a DLCI to a specified Frame Relay subinterface on the router, use the frame-relay interface-dlci interface configuration command. To remove this assignment, use the no form of this command.
Use this command only for subinterfaces on a router. Use of the command on an interface, rather than a subinterface, will prevent the router from forwarding packets intended for that DLCI.
Subinterfaces are logical interfaces associated with a physical interface. To use this command, you must be in subinterface configuration mode. This requires making the logical subinterface assignment before assigning any DLCIs and any encapsulation or broadcast options. See the "Example" section for the sequence of commands.
Use the protocol ip ip-address option only when this router will act as the BOOTP server for autoinstallation over Frame Relay.
For more information about autoinstalling router configuration files over a Frame Relay network, see the "Loading System Images, Microcode Images, and Configuration Files" chapter in the Router Products Configuration Guide.
Table 9-1 lists the frame-relay interface-dlci option keywords.
Table 9-1 Frame Relay Interface-DLCI Option Keywords
| Keyword | Option |
|---|---|
The following example assigns DLCI 100 to subinterface serial 5.17:
Use the frame-relay intf-type interface configuration command to configure a Frame Relay switch type. Use the no form of this command to disable the switch.
This command can be used only if Frame Relay switching has previously been enabled globally by use of the frame-relay switching command.
The following example configures a DTE switch type:
If the Inverse Address Resolution Protocol (InvARP) was previously disabled on a router configured for Frame Relay, use the frame-relay inverse-arp interface configuration command to reenable InvARP. Use the no form of this command to disable this feature.
This implementation of Inverse ARP is based on RFC 1293. It allows a router running Frame Relay to discover the protocol address of a device associated with the virtual circuit.
In Frame Relay, permanent virtual circuits are identified by a DLCI, which is the equivalent of a hardware address. By exchanging signaling messages, a network announces a new virtual circuit, and with Inverse ARP, the protocol address at the other side of the circuit can be discovered.
The show frame-relay map command displays the word "dynamic" to flag virtual circuits that are created dynamically by Inverse ARP.
The following example sets Inverse ARP on an interface running AppleTalk:
clear frame-relay-in1arp
show frame-relay map
To configure an interface to ensure that the associated PVC will always carry outgoing TCP/IP headers in compressed form, use the frame-relay ip tcp header-compression interface configuration command. To disable compression of TCP/IP packet headers on the interface, use the no form of this command.
Active TCP/IP header compression; all outgoing TCP/IP packets are subjected to header compression.
This command applies to interfaces that support Frame Relay encapsulation, specifically serial ports and HSSI.
Frame Relay must be configured on the interface before this command can be used.
TCP/IP header compression and IETF encapsulation are mutually exclusive. If an interface is changed to IETF encapsulation, all encapsulation and compression characteristics are lost.
When you use this command to enable TCP/IP header compression, every IP map will inherit the compression characteristics of the interface, unless header compression is explicitly rejected or modified by using the frame-relay map ip header compression command.
The following example configures serial interface 1 to use the default encapsulation (cisco) and passive TCP header compression:
frame-relay map ip tcp header-compression
To enable the Local Management Interface (LMI) mechanism for serial lines using Frame Relay encapsulation, use the frame-relay keepalive interface configuration command. Use the
no form of this command to disable this capability.
The frame-relay keepalive and keepalive commands perform the same function; both commands enable the keepalive sequence. The keepalive sequence is part of the Local Management Interface (LMI) protocol, so these commands also control the enabling and disabling of the LMI.
When viewing the configuration information using the show configuration command, only the keepalive command setting is included; you will not see the frame-relay keepalive setting.
The following example sets the keepalive timer on the server for a period that is two or three seconds faster (shorter interval) than the interval set on the keepalive timer of the Frame Relay switch. The difference in keepalive intervals ensures proper synchronization between the Cisco server and the Frame Relay switch.
A dagger () indicates that the command is documented in another chapter.
keepalive
frame-relay lmi-t392dce
To set a full status polling interval, use the frame-relay lmi-n391dte interface configuration command. To restore the default interval value, assuming an LMI has been configured, use the no form of this command.
Use this command when the interface is configured as data terminal equipment (DTE) or network-to-network interface (NNI) as a means of setting the full status message polling interval.
In the following example, one out of every four status inquiries generated by the router will request a full status response from the switch. The other three status inquiries will request keepalive exchanges only.
To set the DCE and NNI error threshold, use the frame-relay lmi-n392dce interface configuration command. To remove the current setting, use the no form of this command.
In Cisco's implementation, N392 errors must occur within the number defined by the N393 event count in order for the link to be declared down. Therefore, the threshold value for this command must be less than the count value defined in the frame-relay lmi-n393dce command.
In the following example, the LMI failure threshold is set to three. The router acts as a Frame Relay DCE or NNI switch.
To set the error threshold on a DTE or NNI interface, use the frame-relay lmi-n392dte interface configuration command. To remove the current setting, use the no form of this command.
In the following example, the LMI failure threshold is set to three. The router acts as a Frame Relay DTE or NNI switch.
To set the DCE and NNI monitored events count, use the frame-relay lmi-n393dce interface configuration command. To remove the current setting, use the no form of this command.
This command and the frame-relay lmi-n392dce command define the condition that causes the link to be declared down. In Cisco's implementation, N392 errors must occur within the events count in order for the link to be declared down. Therefore, the events value defined in this command must be greater than the threshold value defined in the frame-relay lmi-n392dce command.
In the following example, the LMI monitored events count is set to three. The router acts as a Frame Relay DCE or NNI switch.
To set the monitored event count on a DTE or NNI interface, use the frame-relay lmi-n393dte interface configuration command. To remove the current setting, use the no form of this command.
In the following example, the LMI monitored events count is set to three. The router acts as a Frame Relay DTE or NNI switch.
To set the polling verification timer on a DCE or NNI interface, use the frame-relay lmi-t392dce interface configuration command. To remove the current setting, use the no form of this command.
The value for the timer must be greater than the DTE or NNI keepalive timer.
The following example indicates a polling verification timer on a DCE or NNI interface set to 20:
To select the Local Management Interface (LMI) type, use the frame-relay lmi-type interface configuration command. To return to the default LMI type, use the no form of this command.
Note The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) carries out the functions of the former Consultative Committee for International Telegraph and Telephone (CCITT).
Cisco's implementation of Frame Relay supports three LMI types: Cisco, ANSI Annex D, and
ITU-T Q.933 Annex A.
The LMI type is set on a per-interface basis and is shown in the output of the show interfaces EXEC command.
The following is an example of the commands you enter to select the ANSI Annex D LMI type:
To set the source DLCI for use when the LMI is not supported, use the frame-relay local-dlci interface configuration command . To remove the DLCI number, use the no form of this command.
Note The frame-relay local-dlci command is provided mainly to allow testing of the Frame Relay encapsulation in a setting where two servers are connected back to back. This command is not required in a live Frame Relay network.
If LMI is supported and the multicast information element is present, the network server sets its local DLCI based on information provided via the LMI.
The following example specifies 100 as the local DLCI:
Use the frame-relay map interface configuration command to define the mapping between a destination protocol address and the DLCI used to connect to the destination address. Use the no form of this command to delete the map entry.
There can be many DLCIs known by a router that can send data to many different places, but they are all multiplexed over one physical link. The Frame Relay map tells the router how to get from a specific protocol and address pair to the correct DLCI.
The optional ietf and cisco keywords allow flexibility in the configuration. If no keywords are specified in the configuration, the map inherits the attributes set with the encapsulation frame-relay command. You can also use the encapsulation options to specify that, for example, all interfaces use IETF encapsulation except one, which needs the original Cisco encapsulation method, and it can be defined using the cisco keyword with the frame-relay map command.
The broadcast keyword provides two functions: It forwards broadcasts when multicasting is not enabled, and it simplifies the configuration of OSPF for nonbroadcast networks that will use Frame Relay.
The broadcast keyword might also be required for some routing protocols—for example, AppleTalk—that depend on regular routing table updates, especially when the router at the remote end is waiting for a routing update packet to arrive before adding the route.
OSPF treats a nonbroadcast, multiaccess network such as Frame Relay much the same way it treats a broadcast network in that it requires selection of a designated router. In previous releases, this required manual assignment in the OSPF configuration using the neighbor interface router command. When the frame-relay map command is included in the configuration with the broadcast, and the ip ospf network command (with the broadcast keyword) is configured, there is no need to configure any neighbors manually. OSPF will now automatically run over the Frame Relay network as a broadcast network. (Refer to the ip ospf network interface command for more detail.)
Note The OSPF broadcast mechanism assumes that IP class D addresses are never used for regular traffic over Frame Relay.
The following example maps the destination IP address 131.108.123.1 to DLCI 100:
OSPF will use DLCI 100 to broadcast updates.
Use the frame-relay map bridge interface configuration command to specify that broadcasts should be forwarded when bridging. Use the no form of this command to delete the map entry.
The following example uses DLCI 144 for bridging:
The following example sets up separate point-to-point links over a subinterface and runs transparent bridging over it:
DLCI 42 is used as the link; see the section "Frame Relay Configuration Examples" in the Router Products Configuration Guide for more examples of subinterfaces.
Use the frame-relay map clns interface configuration command to specify that broadcasts should be forwarded when routing using ISO CLNS. Use the no form of this interface configuration command to delete the map entry.
The following example uses DLCI 125 for ISO CLNS routing:
To assign header compression characteristics to an IP map that differ from the compression characteristics of the interface with which the IP map is associated, use the frame-relay map ip tcp header-compression interface configuration command. To remove the IP map, use the no form of this command.
The default encapsulation is cisco.
To disable TCP/IP header compression on the IP map, use the nocompress form of the command.
IP maps inherit the compression characteristics of the associated interface unless this command is used to provide different characteristics. This command can also be used to reconfigure an IP map that existed before TCP header compression was configured on the associated interface.
When IP maps at both ends of a connection inherit passive compression, the connection will never transfer compressed traffic because neither side will generate a packet with a compressed header.
If you change the encapsulation characteristics of the interface to IETF, you lose the TCP header compression configuration of the associated IP map.
The command frame-relay map ip ip-address dlci tcp header-compression active can also be entered as frame-relay map ip ip-address dlci active tcp header-compression.
The following example illustrates a command sequence configuring an IP map associated with serial interface 1 to enable active TCP header compression:
frame-relay ip tcp header-compression
Use the frame-relay multicast-dlci interface configuration command to define the DLCI to be used for multicasts. Use the no form of this command to remove the multicast group.
Note The frame-relay multicast-dlci command is provided mainly to allow testing of the Frame Relay encapsulation in a setting where two servers are connected back to back. This command is not required in a live Frame Relay network.
Use this command when the multicast facility is not supported. Network transmissions (packets) sent to a multicast DLCI are delivered to all network servers defined as members of the multicast group.
The following example specifies 1022 as the multicast DLCI:
Use the frame-relay route interface configuration command to specify the static route for PVC switching. Use the no form of this command to remove a static route.
The following example configures a static route that allows packets in DLCI 100 and transmits packets out over DLCI 200 on interface serial 2:
The following example illustrates the commands you enter for a complete configuration that includes two static routes for PVC switching between interface serial 1 and interface serial 2:
To instruct the network server to request the short status message from the switch (see Version 2.3 of the joint Frame Relay Interface specification), use the frame-relay short-status interface configuration command. Use the no form of this command to override the default
These commands have no keywords or arguments.
To request the full status message
The following example returns the interface to the default state of requesting full status messages.
Use the frame-relay switching global configuration command to enable PVC switching on a Frame Relay DCE or an NNI. Use the no form of this command to disable switching.
This command has no arguments or keywords.
This command must be added to the configuration file before configuring the routes.
The following example shows the simple command that is entered in the configuration file before the Frame Relay configuration commands to enable switching:
To display statistics and TCP/IP header compression information for the interface, use the show frame-relay ip tcp header-compression EXEC command.
This command has no arguments or keywords.
The following is sample output from the show frame-relay ip tcp header-compression command:
Table 9-2 describes the fields shown in the display.
Table 9-2 Show Frame-Relay IP TCP Header-Compression Field Descriptions
Use the show frame-relay lmi EXEC command to display statistics about the Local Management Interface (LMI).