3Com Router User Manual

							Configure Frame Relay247
Note the following:
■The interfaces link layer protocol can be configured to Frame Relay only when 
it operates in the synchronous mode.
■When the interfaces link layer protocol is SLIP, the physical attributes of the 
interface cannot be modified to synchronous mode. At this time, you should 
first modify the link layer protocol of the interface to PPP and then you may 
change the interface attribute to synchronous mode.
The Frame Relay interface can send the packet in either of the Frame Relay 
formats, while it can recognize and receive packets in both formats. That is, even if 
the format of Frame Relay of opposite equipment is different from that of the 
local, the equipment at the two ends can communicate with each other as long as 
the opposite equipment can recognize the two formats automatically. But when 
the opposite equipment can not recognize the two formats automatically, the 
Frame Relays of equipment at the two ends must be set to the same format.
2Configure Frame Relay Terminal Type
In Frame Relay, the two sides in communication are classified into user side and 
network side. The user side is called DTE, and the network side is called DCE. The 
equipment response interface should be configured as DTE or DCE format 
according to its location in the network. In Frame Relay networks, 
Network-to-Network Interface (NNI) is used between the Frame Relay switches.
In the interface view, perform the following task to configure the type of Frame 
Relay interface as DTE, DCE or NNI. 
Ta b l e 275   Configure Frame Relay interface type
The default type of Frame Relay interface is DTE.
Note the following point: If the terminal type of Frame Relay interface is changed 
to DCE or NNI, 
fr switching should be enabled in the system view. 
3Configure Frame Relay LMI Type
The LMI protocol is used to maintain the PVC lists of Frame Relay protocol, 
including adding PVC records, deleting the records about disconnected PVCs, 
monitoring the change of PVC status, and verifying the link integrity. The 3Com 
Router supports three standard LMI protocols: LMI complying with ITU-T Q.933 
Appendix A, LMI complying with ANSI T1.617 Appendix D and non-standard LMI.
In the interface view, perform the following task to configure the type of LMI 
protocol of Frame Relay interface.
Ta b l e 276   Configure Frame Relay LMI protocol type
OperationCommand
Configure Frame Relay interface typefr interface-type { dte | 
dce | nni }
Restore the Frame Relay interface type to the default valueundo fr interface-type
OperationCommand
Configure Frame Relay LMI protocol typefr lmi type { ansi | 
nonstandard | q933a } [ 
bi-direction ]
Restore the Frame Relay interface LMI protocol type to 
default.undo fr lmi type 
						

							248CHAPTER 17: CONFIGURING FRAME RELAY
When the Frame Relay interface type is DCE or NNI, the default type of LMI 
protocol of interface is Q933a. When the Frame Relay interface type is DTE, the 
default LMI protocol of interface is null.
4Configure the Related Parameters of Frame Relay LMI Protocol
The procedure of the LMI protocol is as follow:
■DTE sends out a status enquiry message, and the timer T391 starts. T391 is set 
with the polling interval. In other words, DTE will send a status enquiry 
message at each interval of T391. Simultaneously, the counter V391 at the DTE 
side will start. If V391 < N391, The status enquiry message sent by DTE will 
only inquire the “link integrity”. If V391 = N391, it will clear all. In this case, 
besides inquiring the “link integrity”, the status enquiry sent by DTE will inquire 
the statuses of all the PVCs, which is called “Full Status Message Polling”.
■Upon receiving the enquiry message, DCE respond to the status enquiry 
message by sending the status message. Simultaneously, the polling 
authentication timer T392 at the DCE side starts, and DCE waits for the next 
status enquiry message. Upon the timeout of T392, if DCE receives no status 
enquiry messages, it will record this error and add 1 to the number of errors.
■Upon receiving the status response message, DTE knows the link status and 
PVC status. When DCE responds to the status enquiry message, it should 
respond the status message of all the PVCs if the PVC status on the network 
changes or there is PVC added or deleted, irrespective of DTE inquires for the 
PVC status or not,. Thereby, DTE can know the changes on DCE side, and 
update the record based on that information.
■If the timer T391 times out, but no status message is received yet at the DTE 
side to respond to that, this event error will be recorded and 1 will be added to 
the number of errors.
■If the number of errors in N393 events exceeds N392, DTE or DCE will assume 
that the path is usable but all the virtual circuits are unusable. N393 represents 
the total number of observed events, and N392 represents the error threshold.
You can configure the various counters and thresholds of the frame relay LMI 
protocol, to optimize the running efficiency of equipment at the DTE and DCE 
sides.
Perform the following configurations in synchronous interface view.
Ta b l e 277   Configure the related parameters of Frame Relay LMI protocol
OperationCommand
Set the counter on PVC status enquiry messages 
(N391 DTE)fr lmi n391dte [ n391-value ]
Restore the default value of the counter on the 
PVC status enquiry messagesundo fr lmi-n391dte
Set the LMI error threshold (N392 DCE)fr lmi n392dce [ n392-value ]
Restore the default value of the LMI error 
thresholdundo fr lmi n392dce
Set the LMI error threshold (N392 DTE)fr lmi n392dte [ n392-value ]
Restore the default value of the LMI error 
thresholdundo fr lmi n392dte
Set the LMI event counter (N393 DTE)fr lmi n393dte [ n393-value ]
Restore the default value of the LMI event 
counterundo fr lmi n393dte
Set the LMI event counter (N393 DCE)fr lmi n393dce [ n393-value ] 
						

							Configure Frame Relay249
The following table describes the value ranges and default values of related 
parameters of the Frame Relay LMI protocol
Ta b l e 278   Descriptions of related parameters of Frame Relay LMI protocol
In which, the related parameters at the DTE side include:
■T391DTE: The interval of the link integrity polling for the equipment at the DTE 
side
■N391DTE: DTE equipment will send a status enquiry message at a certain 
interval (which is determined by T391). The status enquiry messages are divided 
into two types: link integrity authentication messages and link status enquiry 
messages. The parameter N391DTE is used to define the sending ratio of these 
two types of messages. That is:
Number of link integrity authentication messages: Number of link status enquiry 
messages = N391-1: 1
■N392DTE: The threshold for the errors that can occur in the total number of 
observed events at the DTE side.
■N393DTE: The total number of observed events at the DTE side.
DTE equipment will send a status enquiry message at a certain interval (which is 
determined by T391) to inquire the link status. Upon receiving that message, the 
DCE equipment sends the status response message promptly. If the DTE 
equipment does not receive the response in the specified time, the error will be 
recorded. If the number of errors exceeds the threshold, the DTE equipment will 
regard the physical path and all the virtual circuits as unusable. The parameters 
N392 and N393 together define the “error threshold”. That is, if the number of 
errors in the N393 status enquiry messages sent by the DTE equipment reaches 
Restore the default value of the LMI event 
counterundo fr lmi n393dce
Set the link integrity polling timer at the user side 
(T391 DTE)fr lmi t391dte [ t391-value ]
Restore the default value of the link integrity 
polling timer at the user sideundo fr lmi t391dte
Set the polling timer at the network side (T392 
DCE)fr lmi t392dce [ t392-value ]
Restore the default value of the polling timer at 
the network sideundo fr lmi t392dce
Operation 
mode
Parameter descriptionValue rangeDefault value
DTELink integrity polling timer (T391)
When T391 = 0, it indicates that the 
LMI protocol is disabled.
5 to 30 seconds10 seconds
Counter on the PVC full status 
message polling requests (N391)1 to 255 times6 times
Error threshold counter at the user 
side (N392)1 to 10 times3 times
Event counter at the user side (N393)1 to 10 times4 times
DCEPolling authentication timer at the 
network side (T392)5 to 30 seconds15 seconds
Error threshold counter at the 
network side (N392)1 to 10 times3 times
Event counter at the network side 
(N393)1 to 10 times4 times 
						

							250CHAPTER 17: CONFIGURING FRAME RELAY
N392, the DTE equipment will assume that the number of errors reaches the 
threshold, and will regard the physical path and all the virtual circuits as unusable.
The parameters at the DCE side include:
■T392DCE: Define the longest duration for the DCE equipment to wait for a 
status enquiry message. It should be larger than T391.
■N392DCE: The threshold for the errors that can occur in the total number of 
observed events at the DCE side.
■N393DCE: The total number of observed events at the DCE side.
It should be noted that N392 should be no larger than N393 and T391DTE should 
be smaller than its peer T392DCE.
5Configure Frame Relay Address Mapping
Frame Relay address mapping means to establish the mapping between the peer 
protocol address and the local DLCI. Address mapping of Frame Relay can either 
be configured statically or set up dynamically.
aConfigure Frame Relay static address mapping
Static configuration means the manual setup of the mapping relation between 
the peer protocol address and local DLCI, and is usually applied when there are 
few peer hosts or there is a default route. 
In interface view, perform the following task to configure the Frame Relay 
static address mapping.
Ta b l e 279   Configure Frame Relay static address mapping
By default, the dynamic inverse arp is enabled on all the interfaces.
After the Frame Relay static address mapping is configured, the dynamic 
inverse arp will be disabled automatically on the specified DLCI.
bConfigure Frame Relay dynamic inverse arp
Dynamic configuration means the mapping peer protocol address and local 
DLCI dynamically after running the inverse address resolution protocol (Inverse 
ARP), which is applicable when the peer router also supports the inverse 
address resolution protocol and network is complex.
In interface view, perform the following task to configure the dynamic inverse 
arp of Frame Relay.
Ta b l e 280   Configure Frame Relay dynamic address mapping
By default, the dynamic inverse arp is enabled on the interface.
OperationCommand
Add a static address mappingfr map { ip | ipx } protocol-address dlci 
dlci [ broadcast ] [ nonstandard | ietf ] 
[ logic-channel channel_number ] [ 
nocompress | compression vj ] [ 
compression frf9 ]
Delete a static address mappingundo fr map { ip | ipx } protocol-address 
dlci dlci
OperationCommand
Enable dynamic address mappingfr inarp [ { ip | ipx } [ dlci ] ]
Disable dynamic address mappingundo fr inarp [ { ip | ipx } [ dlci ] ] 
						

							Configure Frame Relay251
The map created through the dynamic inverse ARP has broadcast attribute.
6Configure Frame Relay Local Virtual Circuit Number
Perform the following configurations in synchronous serial interface view.
Ta b l e 281   Configure Frame Relay local virtual circuit number
After entering the DLCI view through the fr dlci command, the user can 
configure the parameters associated with this virtual circuit, such as Frame Relay 
class.
The virtual circuit number is valid locally, that is, the virtual circuit numbers on both 
ends of the link can be the same. Different interfaces can be assigned with the 
same virtual circuit number, but the virtual circuit number must be unique on one 
physical interface.
When the Frame Relay interface type is DCE or NNI, the interface (either main 
interface or sub-interface) should be configured manully with virtual circuits. 
When the Frame Relay interface type is DTE, for the main interface, the system will 
determine the virtual circuit automatically according to the opposite equipment; 
the sub-interface must be configured with virtual circuits manually.
7Configure Frame Relay Sub-Interface 
The Frame Relay interface is a kind of NBMA (Non-Broadcast Multi-Access) 
interface, which supports sub-interfaces. The Frame Relay module has two types 
of interfaces: main interface and sub-interface. The sub-interface is logical 
interface and can be used to configure protocol address and virtual circuit. One 
physical interface can include multiple sub-interfaces, which do not exist 
physically. However, for the network layer, both the sub-interface and main 
interface can be used to configure the virtual circuit to connect to remote 
equipment.
The sub-interfaces of Frame Relay fall into two types: point-to-point sub-interface, 
used to connect a single remote object and point-to-multipoint sub-interface, 
used to connect multiple remote objects in the same network segment. 
The address mapping relation between the frame-relay sub-interfaces can be 
configured manually, or dynamically established by using the inverse ARP. For a 
point-to-point sub-interface, you only need configure one PVC on this 
sub-interface, since there is only one peer device. For a point-to-multipoint 
sub-interface, you can configure multiple PVCs. Each PVC can establish the 
address mapping with its connected peer through running the inverse dynamic 
ARP. Thereby, different PVCs can reach their peers without confusing. 
Alternatively, you can respectively establish different static address mapping for 
these PVCs.
aCreating Frame Relay Sub-Interface
In the interface view, perform the following task to create a sub-interface.
Ta b l e 282   Create Frame Relay sub-interface
OperationCommand
Assign a virtual circuit number to Frame Relay interfacefr dlci dlci-number
Remove the virtual circuit number of Frame Relay 
interfaceundo fr dlci dlci-number
OperationCommand
Enter interface viewinterface type number 
						

							252CHAPTER 17: CONFIGURING FRAME RELAY
bConfigure virtual circuit of Frame Relay sub-interface
In interface view, perform the following task to configure the virtual circuit of 
Frame Relay sub-interface.
Ta b l e 283   Configure virtual circuit of Frame Relay sub-interface
cConfigure Sub-Interface PVC and Establish Address Mapping
Since there is only one peer address for point-to-point sub-interface, the peer 
address is determined when a PVC is configured for the sub-interface. For 
point-to-multipoint sub-interface, the peer address and local DLCI can be 
determined by configuring static address mapping or using inverse address 
resolution protocol.
Establishing static address mapping of Frame Relay sub-interface
Ta b l e 284   Establish static address mapping
Applying dynamic address mapping to the sub-interface
Ta b l e 285   Configure Frame Relay dynamic address mapping
By default, all the sub-interfaces are enabled to use dynamic inverse-arp.
8Configure Frame Relay PVC Switching
Router routers can be used as Frame Relay switches to provide the function of 
Frame Relay PVC switching. There are two ways to configure the Frame Relay 
switching:
 configuring the Frame Relay switched route or configuring the Frame 
Relay switched PVC.
aEnable the Frame Relay switching
Configure interface link layer protocol to 
Frame Relaylink-protocol fr [ ietf | 
nonstandard ]
Create frame-relay sub-interface and enter 
the sub-interface viewinterface type 
number.subinterface-number 
[multipoint | point-to-point ]
Delete the frame-relay sub-interfaceundo interface type 
number.sub-number
OperationCommand
Configure a virtual circuitfr dlci dlci-number
Remove a virtual circuit undo fr dlci dlci-number
OperationCommand
Establish address mappingfr map { ip | ipx } 
protocol-address dlci dlci [ 
broadcast ] [ nonstandard | ietf ] 
[ logic-channel channel_number ] [ 
nocompress | compression vj ] [ 
compression frf9 ]
Delete an address mappingundo fr map { ip | ipx } 
protocol-address dlci dlci
OperationCommand
Enable dynamic address mappingfr inarp [ { ip | ipx } [ dlci ] ]
Disable dynamic address mappingundo fr inarp [ { ip | ipx } [ dlci 
] ] 
						

							Configure Frame Relay253
Perform “Enabling/Disabling Frame Relay PVC switching” in system view, and 
configure all the other commands in synchronous serial interface view.
Ta b l e 286   Configure the Frame Relay PVC switching
By default, Frame Relay PVC switching is disabled.
The configured PVC can take effect only when the type of Frame Relay 
interface is NNI or DCE.
bConfigure Frame Relay switched route
Perform the following configurations in synchronous serial interface view.
Ta b l e 287   Configure the Frame Relay local virtual circuit number
Perform the following configurations in interface view.
Ta b l e 288   Configure the route for Frame Relay PVC switching
By default, the Frame Relay switched route is not configured.
PVC switching can take effect only when the fr dlci-switch command is 
configured on the two interfaces on the Frame Relay switched routers.
cConfigure Frame Relay switched PVC
Perform the following configurations in interface view.
Ta b l e 289   Configure Frame Relay local switched PVC number
Perform the following configurations in system view.
Ta b l e 290   Configure the Frame Relay switched PVC
OperationCommand
Enable the Frame Relay to carry out PVC 
switchingfr switching
Disable the Frame Relay to carry out PVC 
switchingundo fr switching
Set the Frame Relay interface typefr interface-type { dte | dce | 
nni }
OperationCommand
Assign a PVC number for Frame Relay interfacefr dlci dlci-number
Delete the PVC number of Frame Relay interfaceundo fr dlci dlci-number
OperationCommand
Configure the route for Frame Relay PVC 
switchingfr dlci-switch in-dlci 
interface type number dlci 
out-dlci
Delete the route for Frame Relay PVC switchingundo fr dlci-switch in-dlci
OperationCommand
Assign a switched PVC number for the main 
interface or the sub-interfacefr dlci dlci-number
Delete the switched PVC number for the main 
interface or the sub-interfaceundo fr dlci dlci-number
OperationCommand
Configure the Frame Relay switched PVCfr switch name interface type 
number dlci dlci interface type 
number dlci dlci
Delete the Frame Relay switched PVCundo fr switch name 
						

							254CHAPTER 17: CONFIGURING FRAME RELAY
By default, no Frame Relay switched PVC is created.
After configuring the Frame Relay switched PVC, the user will enter the frame 
relay switch 
view to perform the operations of shutdown and undo shutdown 
on the switched PVC.
The differences between configuring a Frame Relay switched route and 
configuring a Frame Relay switched PVC are listed below:
1) A Frame Relay switched route can become valid only when it is configured on 
the two Frame Relay switched interfaces, whereas a Frame Relay switched PVC can 
become valid as soon as it is configured in system view for once.
2) After the Frame Relay switched PVC is configured, the user will enter the frame 
relay switch view. At this time, the user can perform the operations of 
shutdown 
and 
undo shutdown on the switched PVC. However, the user cannot do that on a 
Frame Relay switched route.
Configure Multilink 
Frame Relay (FRF.16) Overview
Multilink Frame Relay can bundle multiple low-rate Frame Relay links to form a 
Frame Relay with high rate and wide bandwidth. Multilink Frame Relay creates a 
virtual Frame Relay interface which contains multiple Frame Relay physical 
interfaces. In this way, the bandwidth of the virtual Frame Relay is equal to the 
sum of the bandwidth of each Frame Relay physical interface contained in the 
virtual Frame Relay interface.
The virtual Frame Relay interface is called “Bundle”, and the physical interfaces 
contained in the virtual interface is called “bundle link”. As for an actual physical 
layer, bundle link is equal to an analog data link layer, and bundle manages all the 
bundle links. As for data link layer, bundle is analog physical layer.
Figure 80   Illustration of the relationship between bundle and bundle links
On the Router Routers, the virtual Frame Relay interface is called “MFR interface”. 
One MFR interface corresponds to one bundle, and one physical interface 
corresponds to a bundle ink. The management performed on the bundle and 
bundle link is actually the management to the MFR interface and the physical 
interface.
After the Frame Relay physical interface is bundle to an MFR interface, the 
network layer parameters and Frame Relay link layer parameters configured on it 
Bundle Link
Physical Interface
Bundle Link
Physical Interface
Bundle
Frame Relay Protocol
Layer 3 Applications
Bundle Link
Physical Interface
Bundle Link
Physical Interface
Bundle
Frame Relay Protocol
Layer 3 Applications
Bundle Bundle LinkBundle Link 
						

							Configure Frame Relay255
will not take effect. On the MFR interface, you can configure the network layer 
parameters (e.g., IP address) and Frame Relay parameters (e.g., DLCI). The physical 
interface bundled on the MFR interface will use the parameters on the MFR 
interface. 
Configure MFR
The configuration tasks of the MFR are listed as follows:
■Configure a MFR Bundle
■Configure a MFR Bundle Link
1Configure a MFR bundle
Please perform the following configuration in system view.
Ta b l e 291   Configure a MFR bundle interface (MFR interface)
By default, no MFR bundle interface is configured.
Please perform the following configuration in MFR interface view.
Ta b l e 292   Configure MFR interface parameter
The default bundle identification s “mfr” plus the bundle number, for example, 
“mfr1. 
By default, the maximum number of the fragments allowed by the MFR interface 
is the same with the number of the physical interfaces bundled to it. 
By default, the voice packets are sent on the multiple physical interfaces bundled 
to the MFR interface by turns.
2Configure a MFR bundle link
Please perform the following configuration in synchronous serial interface view.
Ta b l e 293   Configure physical interfaces link layer protocol to Multilink Frame Relay
By default, no MFR bundle link is created. To remove the association between the 
physical interface and the MFR interface, configure the interfaces link layer 
protocol to a none MFR type using the
 link-protocol command.
Please perform the following configuration in synchronous serial interface view.
OperationCommand
Configure or enter a MFR bundle interfaceinterface mfr number [ 
.subnumber ] [ multipoint | 
point-to-point ]
Remove a MFR bundle interfaceundo interface mfr number [ 
.subnumber ]
OperationCommand
configure bundle identificationmfr bundle-name name
Restore the default bundle identificationundo mfr bundle-name
Set the maximum number of the fragments 
allowed by the MFR interface.mfr window-size number
OperationCommand
Configure physical interfaces link layer protocol to 
Multilink Frame Relay and associate the link with a 
bundle.link-protocol fr mfr number [ 
name ] 
						

							256CHAPTER 17: CONFIGURING FRAME RELAY
Ta b l e 294   Configure the parameters of the bundle link interface
The default link identification is the name of its physical interface. 
By default, a bundle link will send out hello message every 10 seconds; it will send 
a hello message a maximum of 3 times and wait 4 seconds for a hello message 
acknowledgement.
Configure Frame Relay 
Payload Compression 
(FRF.9)Introduction to Frame Relay Payload Compression
Using the Frame Relay payload compression technique to compress Frame Relay 
packets can effectively save the network bandwidth, and reduce the network load, 
hence fulfilling the highly efficient data transmission over the Frame Relay 
networks.
The 3Com Routers adopt FRF.9 standard to implement Frame Relay payload 
compression.
 When applied to the Frame Relay lines with relatively low 
bandwidth, Frame Relay payload compression can achieve significant effect.
 
Frame Relay Compression Configuration
Frame Relay interfaces fall into two types: point-to-point interface and multipoint 
interface.
 The methods of configuring Frame Relay payload compression are 
different for these two types of interfaces.
1Configure Frame Relay payload compression on point-to-point interface
Perform the following configurations in interface view.
Ta b l e 295   Configure Frame Relay compression on point-to-point interface
By default, Frame Relay payload compression is disabled.
On the 3Com Router, only the Frame Relay sub-interfaces can be point-to-point 
interfaces.
2Configure Frame Relay payload compression on multipoint interface
OperationCommand
configure link identification of the multilink Frame relay 
bundle linkmfr link-name name
Restore the default link identificationundo mfr link-name
Set the time interval for the bundle link to send Hello 
messagesmfr timer hello seconds
Restore the default of the time interval for the bundle 
link to send Hello messagesundo mfr timer hello
Set the number of times that the Frame Relay bundle 
link waits for the acknowledge timer to time out 
successivelymfr retry number
Restore the default value of the number of times that 
the Frame Relay bundle link waits for the acknowledge 
timer to time out successivelyundo mfr retry
Set the time that the Frame Relay bundle link waits for 
the remote end to acknowledge the Hello messagemfr timer ack seconds
Restore the default number of the time that the Frame 
Relay bundle link waits for the remote end to 
acknowledge the Hello messageundo mfr timer ack
CompressionCommand
Enable Frame Relay compressionfr compression frf9
Disable Frame Relay compressionundo fr compression frf9