3Com Router User Manual

							Typical X.25 Configuration Example237
[Router-fr-dlci-100]x25-template profile1
[Router-fr-dlci-100]quit
iMap the Frame Relay address to the destination IP address.
[Router-Serial1]fr map ip 202.38.163.252 100
2Configure RouterB:
aCreate an X.25 template.
[Router]x25 template profile1
bConfigure the local X.25 address.
[Router-x25-profile1]x25 x121-address 20094
cMap the destination X.25 address to the destination IP address.
[Router-x25-profile1]x25 map ip 202.38.163.251 x121-address 10094
[Router-x25-profile1]quit
dConfigure an IP address for the local interface.
[Router]interface serial 1
[Router-Serial1]ip address 202.38.163.252 255.255.255.0
eConfigure the link layer protocol of the interface to Frame Relay.
[Router-Serial1]link-protocol fr
[Router-Serial1]fr interface-type dte
fConfigure a Frame Relay DLCI.
[Router-Serial1]fr dlci 100
gConfigure the DLCI to be Annex G DLCI.
[Router-fr-dlci-100]annexg dte
hAssociates an X.25 template with the DLCI.
[Router-fr-dlci-100]x25-template profile1
[Router-fr-dlci-100]quit
iMap the Frame Relay address to the destination IP address.
[Router-Serial1]fr map ip 202.38.163.251 100
SVC Application of X.25 
over Frame RelayI. Networking Requirements
RouterA and RouterC are respectively connected to RouterB and RouterD through 
X.25. RouterB and RouterC are connected through Frame Relay. Configure Annex 
G DLCI 100 for Frame Relay on both RouterB and RouterC to interconnect the two 
X.25 networks. Thereby, PC1 and PC2 can access each other. 
						

							238CHAPTER 16: CONFIGURING LAPB AND X.25
II. Networking Diagram
Figure 78   Networking for the SVC application of X.25 over Frame Relay
III. Configuration Procedure
1Configure the router Router A:
aConfigure the basic X.25 parameters.
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dte ietf
[Router-Serial0]x25 x121-address 1
[Router-Serial0]x25 map ip 1.1.1.2 x121-address 2
[Router-Serial0]ip address 1.1.1.1 255.0.0.0
2Configure the router Router D:
aConfigure the basic X.25 parameters:
[Router]config
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dte ietf
[Router-Serial0]x25 x121-address 2
[Router-Serial0]x25 map ip 1.1.1.1 x121-address 1
[Router-Serial0]ip address 1.1.1.2 255.0.0.0
3Configure the router Router B: 
aEnable X.25 switching.
[Router]x25 switching
bEnable switching on Frame Relay DCE.
[Router]fr switching
cConfigure Serial 0 as the X.25 interface.
[Router]interface serial 0
[Router-Serial0]switching x25 dce ietf
dConfigure Serial 1 as the Frame Relay interface.
[Router]interface serial 1
[Router-Serial1]link-protocol frame-relay
[Router-Serial1]fr interface-type dce
eConfigure a Frame Relay Annex G DLCI.
[Router-Serial1]fr dlci 100
[Router-fr-dlci-100]annexg dce
fConfigure local X.25 switching.
PC1
S0
S0S0
S0
PC2
E0 E0Router B
Router ARouter C
Router DS1 S1DLCI100 
						

							Typical X.25 Configuration Example239
[Router]x25 switch svc 1 interface serial 0
gConfigure X.25 over Frame Relay switching.
[Router]x25 switch svc 2 interface serial 1 dlci 100
4Configure the router Router C:
aEnable X.25 switching.
[Router]x25 switching
bConfigure Serial 0 as the X.25 interface.
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dce ietf
cConfigure Serial 1 as the Frame Relay interface.
[Router]interface serial 1
[Router-Serial1]link-protocol fr
dConfigure the Frame Relay Annex G DLCI.
[Router-Serial1]fr dlci 100
eConfigure local X.25 switching.[Router-fr-dlci-100]annexg dte
[Router]x25 switch svc 2 interface serial 0
fConfigure X.25 over Frame Relay switching.
[Router]x25 switch svc 1 interface serial 1 dlci 100
PVC Application of X.25 
over Frame RelayI. Networking Requirements
RouterA and RouterC are respectively connected to RouterB and RouterD through 
X.25. RouterB and RouterC are connected through Frame Relay. Configure Frame 
Relay Annex G DLCI 100 on both RouterB and RouterC to set up an X.25 PVC to 
interconnect the two X.25 networks. Thereby, PC1 and PC2 can access each other.
II. Networking Diagram
Figure 79   Networking for the PVC application of X.25 over Frame Relay
III. Configuration Procedure
1Configure Router A:
aConfigure the basic X.25 parameters.
[Router]interface serial 0
[Router-Serial0]switch svc x25 dte ietf
PC1
S0
S0S0
S0
PC2
E0 E0Router B
Router ARouter C
Router DS1 S1DLCI100 
						

							240CHAPTER 16: CONFIGURING LAPB AND X.25
[Router-Serial0]x25 x121-address 1
[Router-Serial0]x25 vc-range in-channel 10 20 bi-channel 30 1024
[Router-Serial0]x25 pvc 1 ip 1.1.1.2 x121-address 2
[Router-Serial0]ip address 1.1.1.1 255.0.0.0
2Configure Router D:
aConfigure the basic X.25 parameters.
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dte ietf
[Router-Serial0]x25 x121-address 2
[Router-Serial0]x25 vc-range in-channel 10 20 bi-channel 30 1024
[Router-Serial0]x25 pvc 1 ip 1.1.1.1 x121-address 1
[Router-Serial0]ip address 1.1.1.2 255.0.0.0
3Configure Router B:
aEnable X.25 switching.
[Router]x25 switching
bEnable switching on Frame Relay DCE.
[Router]fr switching
cConfigure Serial 0 as the X.25 interface.
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dce ietf
[Router-Serial0]x25 vc-range in-channel 10 20 bi-channel 30 1024
dConfigure an X.25 template.
[Router]x25 template profile1
[Router-x25-profile1]x25 vc-range in-channel 10 20 bi-channel 30 
1024
[Router-x25-profile1]x25 pvc 1 interface serial 0 pvc 1
eConfigure S1 as the Frame Relay interface.
[Router]interface serial 1
[Router-Serial1]link-protocol fr
[Router-Serial1]fr interface-type dce
fConfigure a Frame Relay Annex G DLCI.
[Router-Serial1]fr dlci 100
[Router-fr-dlci-100]annexg dce
gApply the X.25 template to Annex G DLCI 100 (which is equivalent to 
configure X.25 attributes for the Annex G DLCI).
[Router-fr-dlci-100]x25-template profile1
4Configure Router C:
aEnable X.25 switching.
[Router]x25 switching
bConfigure Serial 0.
[Router]interface serial 0
[Router-Serial0]link-protocol x25 dce ietf
[Router-Serial0]x25 vc-range in-channel 10 20 bi-channel 30 1024
cConfigure an X.25 template.
[Router]x25 template profile1 
						

							Fault Diagnosis and Troubleshooting of LAPB241
[Router-x25-profile1]x25 vc-range in-channel 10 20 bi-channel 30 
1024
[Router-x25-profile1]x25 pvc 1 interface serial 0 pvc 1
5Configure Serial 1.
aConfigure S1 as the Frame Relay interface.
[Router]interface serial 1
[Router-Serial1]link-protocol frame-relay
bConfigure a Frame Relay Annex G DLCI.
[Router-Serial1]fr dlci 100
[Router-fr-dlci-100]annexg dte
cApply the X.25 template to Annex G DLCI 100 (which is equivalent to 
configure X.25 attributes for the Annex G DLCI).
[Router-fr-dlci-100]x25-template profile1
Fault Diagnosis and 
Troubleshooting of 
LAPBFault 1: Two connected sides use X.25 link layer protocol (or LAPB), but the 
protocol is always disconnected. Turn on the debugging switch. It is found 
that one end sends SABM frame, while the other end sends FRMR frame 
circularly.
Troubleshooting: this is because both sides worked in the same working mode 
(DTE or DCE). Change the working mode of one side to solve the problem.
Fault 2: Two connected sides use X.25 link layer protocol, and the protocol 
is already in UP status, but cannot ping through the peer. Turn on the 
debugging switch and it is found that the received frames are discarded 
on one end instead of being forwarded up to the packet layer.
Troubleshooting: The maximum frame bits of this end may be too small. Change 
the configuration.
Fault Diagnosis and 
Troubleshooting of 
X.25This section describes some common faults and the troubleshooting methods. 
Assuming that the connection of the X.25 layer 2 (LAPB) is completely correct.
Fault 1: LAPB is already in Connect status, but the X.25 protocol can not 
enter UP status.
Troubleshooting: It is possible that the local working mode has been configured 
wrong, for example, both sides of a connection are DTE or DCE. Try again after 
changing the interface working mode.
Fault 2: X.25 protocol is UP, but virtual circuit can not be established, i.e., 
unable to ping through.
This may be caused by one of the following:
■Local X.121 address not configured
■Address mapping to the peer not configured
■Opposite X.121 address not configured
■Address mapping from peer to local not configured
■Channel range not correct 
						

							242CHAPTER 16: CONFIGURING LAPB AND X.25
■Facility options inhibited by network have been carried.
Troubleshooting: if the address is configured incorrectly, change the configuration. 
For the last two causes, please consult the network management department for 
correct channel range and permissible facility options.
Fault 3: The virtual circuit can be established, but is frequently reset or 
cleared during data transmission.
Troubleshooting: It is very likely that the flow control parameters are set 
incorrectly. For the back to back direct connection, check the sending window and 
receiving window of the local and peer to see whether they match each other. In 
case it is connected to public packet networks, consult the network management 
department to correct flow control parameters.
Fault 4: The request to set Permanent virtual circuits (PVCs) is rejected.
Troubleshooting: if the channel section of the permanent virtual circuit is disabled, 
the X.25 will reject the request to set a permanent virtual circuit. In this case, 
simply enable the permanent virtual circuit channel section.
Fault 5: After configuring SVC application of XOT, you cannot ping 
through
Troubleshooting: there are various reasons. You may first check if the physical and 
protocol statuses of the interface are UP. If the interface status is DOWN, check if 
the physical connection and bottom configuration are correct. If the interface is 
properly configured, then check the SVC configuration. If SVC is also properly 
configured, check the XOT configuration. 
Fault 6: After configuring PVC application of XOT, you cannot ping 
through
Troubleshooting: there are various reasons. You may first check if the physical and 
protocol statuses of the interface are UP. If the interface status is DOWN, check if 
the physical connection and configuration are correct. If the interface is properly 
configured, then check the PVC configuration. If PVC is also properly configured, 
check the XOT configuration.
Fault 7: Annex G DLCI is used for interconnection, the link layer protocol is 
up, and DLCI has been in place after negotiation. However, the remote end 
cannot be pinged.
Troubleshooting:
■Check whether the X.25 protocol is up at both ends of the Annex G DLCI by 
using the 
display fr pvc-info command. Both the Frame Relay interface 
and DLCI number should be explicitly specified in the command.
■Check whether the proper map between the Frame Relay address and the 
destination IP address has been configured on the router at each ends.
■Check whether the proper X.25 template has been configured for the Annex G 
DLCI on each ends, and whether the local X.121 address has been correctly 
mapped to the X.25 address for the destination IP address on each ends.
■Check whether X.25 SVC has been correctly set up by executing the display 
x25 vc
 command. 
						

							Fault Diagnosis and Troubleshooting of X.25243
■If receiving the ping packet forwarded from the router at one end, check 
whether the returning route has been configured in the routing table. In 
addition, if the destination IP address for returning the packets is different from 
that configured in the Frame Relay address map and X.25 address map, you 
need to reconfigure the maps. 
■If multiple X.25 address maps for reaching the same destination X.121 address 
have been configured in an X.25 template, check whether the 
x25 
vc-per-map 
command has been configured so that multiple X.25 SVC calls 
can be placed with the same X.25 address map. Use the 
debugging x25 
command to debug the X.25 protocol. 
						

							244CHAPTER 16: CONFIGURING LAPB AND X.25 
						

							17
CONFIGURING FRAME RELAY
This chapter contains information on the following topics:
■Frame Relay Protocol Overview
■Configure Frame Relay
■Configure Frame Relay QoS
■Configure Frame Relay over Other Protocols
■Display and debug Frame Relay
■Typical Frame Relay Configuration Example
■Fault Diagnosis and Troubleshooting of Frame Relay
Frame Relay Protocol 
OverviewFrame Relay protocol is a fast-packaging switching technology, which develops on 
the basis of X.25 technology. Compared with X.25 protocol, Frame Relay only 
implements the core function of the link layer, easily and efficiently.
A Frame Relay network provides capacity of data communication between user 
equipment (such as routers and hosts), also called data terminal equipment (DTE). 
The equipment that provides access for DTE is data circuit-terminating equipment 
(DCE). A Frame Relay network can be a public network, a private enterprise 
network, or a network formed by direct connection between data equipment.
The Frame Relay protocol is a statistics multiplexing protocol, providing multiple 
virtual circuits on a single physical transmission line. Each virtual circuit is identified 
by a DLCI (Data Link Connection Identifier), which is valid only on the local 
interface and the corresponding opposite interface. This means that in the same 
Frame Relay network, the same DLCI on different physical interfaces does not 
indicate the same virtual connection. A user interface in the Frame Relay network 
supports up to 1024 virtual circuits, among which the DLCI range available to the 
user is 16~1007. As a Frame Relay virtual circuit is connection oriented, different 
local DLCIs are connected to different opposite equipment. Therefore, the local 
DLCI can be considered as the Frame Relay address of the opposite equipment.
Frame relay address mapping associates the opposite equipments protocol 
address with its Frame Relay address (local DLCI), so that the upper layer protocol 
can locate the opposite equipment by using its protocol address. Frame Relay 
mainly bears IP. In sending IP packet, only the next hop address of the packet can 
be obtained from the route table, so this IP address must be used to determine the 
corresponding DLCI before sending. This process can be performed by searching 
for the Frame Relay address mapping table, because the mapping relation 
between the opposite IP address and the next hop DLCI is stored in the address 
mapping table. The address mapping table can be manually configured, or 
maintained dynamically by the Inverse ARP protocol. 
						

							246CHAPTER 17: CONFIGURING FRAME RELAY
Virtual circuits can be divided into permanent virtual circuit and switching virtual 
circuit, according to their different configuration method. Virtual circuits 
configured manually are called Permanent virtual circuits (PVCs), and those created 
by protocol negotiation are called switching virtual circuits (SVCs), which are 
automatically created and deleted by Inverse ARP protocol. At present, the most 
frequently used in Frame Relay is the permanent virtual circuit mode, i.e., manually 
configured virtual circuit.
In the permanent virtual circuit mode, test the availability of the virtual circuit, 
which is accomplished by the local management interface (LMI) protocol. The 
3Com Router supports three LMI protocols: LMI complying with ITU-T Q.933 
Appendix A, LMI complying with ANSI T1.617 Appendix D and non-standard LMI. 
Their basic function is: DTE sends one Status Enquiry packet to query the virtual 
circuit status at certain interval, after the DCE receives the packet, it will 
immediately use the Status packet to inform DTE the status of all the virtual 
circuits on current interface.
The status of Permanent virtual circuits (PVCs) on DTE is completely determined by 
DCE. And the network determines the status of Permanent virtual circuits (PVCs) 
of DCE. In case that the two network devices are directly connected, the 
equipment administrator sets the virtual circuit status of DCE. In The 3Com Router, 
the quantity and status of the virtual circuits are set at the time when address 
mapping is set (with the 
fr map command). They can also be configured with the 
Frame Relay local virtual circuit configuration command (
fr dlci command).
Configure Frame Relay Frame Relay configuration includes:
■Configure the Link Layer Protocol of the Interface to Frame Relay
■Configure Frame Relay Terminal Type
■Configure Frame Relay LMI Type
■Configure the Related Parameters of Frame Relay LMI Protocol
■Configure Frame Relay Address Mapping
■Configure Frame Relay Local Virtual Circuit Number
■Configure Frame Relay Sub-Interface
■Configure Frame Relay PVC Switching
■Configure Multilink Frame Relay (FRF.16)
■Configure Frame Relay Payload Compression (FRF.9)
■Enable/Disable TCP/IP Header Compression on Interfaces
■Configure Frame Relay Fragment(FRF.12)
1Configure the Link Layer Protocol of the Interface to Frame Relay
Perform the following task in the interface view.
Ta b l e 274   Configure the link layer protocol of interface to Frame Relay
By default, the interfaces link layer protocol is PPP.
OperationCommand
Configure the link layer protocol of interface to Frame 
Relaylink-protocol fr [ ietf | 
nonstandard ]