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In preparation of your CCNP exam, we want to make sure we cover the various concepts that we could see on your Cisco CCNP exam. So to assist you, below we will discuss on of the more difficult CCNP concepts; Great Frame Relay Information. As you progress through your CCNP exam studies, I am sure with repetition you will find this topic becomes easier. So even though it may be a difficult concept and confusing at first, keep at it as no one said getting your Cisco certification would be easy!
Introduction Frame Relay is an industry-standard, switched data link layer protocol that handles multiple virtual circuits using High-Level Data Link Control (HDLC) encapsulation between connected devices. In many cases, Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement. The following figure illustrates a Frame Relay frame (ANSI T1.618).
 Note in the above figure, Q.922 addresses, as presently defined, are two octets and contain a 10-bit data-link connection identifier (DLCI). In some networks Q.922 addresses may optionally be increased to three or four octets.
The "flag" fields delimit the beginning and end of the frame. Following the leading "flag" field are two bytes of address information. Ten bits of these two bytes make up the actual circuit ID (called the DLCI, for data-link connection identifier).
The 10-bit DLCI value is the heart of the Frame Relay header. It identifies the logical connection that is multiplexed into the physical channel. In the basic (that is, not extended by the Local Management Interface [LMI]) mode of addressing, DLCIs have local significance; that is, the end devices at two different ends of a connection may use a different DLCI to refer to that same connection.
Before You Begin Conventions For more information on document conventions, see the Cisco Technical Tips Conventions.
Prerequisites For more information and definitions for the terms used in this document, please refer to the Frame Relay Glossary
Components Used This document is not restricted to specific software and hardware versions.
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
Background Theory Frame Relay was originally conceived as a protocol for use over ISDN interfaces. Initial proposals to this effect were submitted to the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) (formerly the Consultative Committee for International Telegraph and Telephone [CCITT]) in 1984. Work on Frame Relay was also undertaken in the ANSI-accredited T1S1 standards committee in the United States.
In 1990, Cisco Systems, StrataCom, Northern Telecom, and Digital Equipment Corporation formed a consortium to focus Frame Relay technology development and accelerate the introduction of inter operable Frame Relay products. They developed a specification conforming to the basic Frame Relay protocol being discussed in T1S1 and ITU-T, but extended it with features that provide additional capabilities for complex internetworking environments. These Frame Relay extensions are referred to collectively as the LMI. This is the "cisco" LMI in the router as opposed to the "ansi" or "q933a" LMI.
Frame Relay provides a packet-switching data communications capability that is used across the interface between user devices (such as routers, bridges, host machines) and network equipment (such as switching nodes). User devices are often referred to as data terminal equipment (DTE), while network equipment that interfaces to DTE is often referred to as data circuit-terminating equipment (DCE). The network providing the Frame Relay interface can be either a carrier-provided public network or a network of privately owned equipment serving a single enterprise.
Frame Relay differs significantly from X.25 in its functionality and format. In particular, Frame Relay is a more streamlined protocol, facilitating higher performance and greater efficiency.
As an interface between user and network equipment, Frame Relay provides a means for statistically multiplexing many logical data conversations (referred to as virtual circuits) over a single physical transmission link. This contrasts with systems that use only time-division-multiplexing (TDM) techniques for supporting multiple data streams. Frame Relay's statistical multiplexing provides more flexible and efficient use of available bandwidth. It can be used without TDM techniques or on top of channels provided by TDM systems.
Another important characteristic of Frame Relay is that it exploits the recent advances in wide-area network (WAN) transmission technology. Earlier WAN protocols, such as X.25, were developed when analog transmission systems and copper media were predominant. These links are much less reliable than the fiber media/digital transmission links available today. Over links such as these, link-layer protocols can forego time-consuming error correction algorithms, leaving these to be performed at higher protocol layers. Greater performance and efficiency is therefore possible without sacrificing data integrity. Frame Relay is designed with this approach in mind. It includes a cyclic redundancy check (CRC) algorithm for detecting corrupted bits (so the data can be discarded), but it does not include any protocol mechanisms for correcting bad data (for example, by retransmitting it at this level of protocol).
Another difference between Frame Relay and X.25 is the absence of explicit, per-virtual-circuit flow control in Frame Relay. Now that many upper-layer protocols are effectively executing their own flow control algorithms, the need for this functionality at the link layer has diminished. Frame Relay, therefore, does not include explicit flow control procedures that duplicate those in higher layers. Instead, very simple congestion notification mechanisms are provided to allow a network to inform a user device that the network resources are close to a congested state. This notification can alert higher-layer protocols that flow control may be needed.
Configuring Basic Frame Relay Once you have reliable connections to the local Frame Relay switch at both ends of the permanent virtual circuit (PVC), then it is time to start planning the Frame Relay configuration. In this first example, the Local Management Interface (LMI)-type defaults to "cisco" LMI on Spicey. An interface is by default a "multipoint" interface so, frame-relay inverse-arp is on (for point-to-point, there is no Inverse ARP). IP split horizon checking is disabled by default for Frame Relay encapsulation, so routing updates come in and out the same interface. The routers learn the data-link connection identifiers (DLCIs) they need to use from the Frame Relay switch via LMI updates. The routers then Inverse ARP for the remote IP address and create a mapping of local DLCIs and their associated remote IP addresses.
Network Diagram
Configurations
debug and show Commands Before issuing debug commands, please see Important Information on Debug Commands.
- show frame-relay map
- show frame-relay pvc
- show frame-relay lmi
- ping
- show ip route
Spicey Spicey#show frame-relay map
Serial0 (up): ip 3.1.3.2 dlci 140(0x8C,0x20C0), dynamic,
broadcast,, status defined, active
Spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0
input pkts 83 output pkts 87 in bytes 8144
out bytes 8408 dropped pkts 0 in FECN pkts0
in BECN pkts 0 out FECN pkts 0 out BECN pkts0
in DE pkts 0 out DE pkts 0
out bcast pkts 41 out bcast bytes 3652
pvc create time 01:31:50, last time pvc status changed 01:28:28
Spicey#show frame-relay lmi
LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0
Num Status Enq. Sent 550 Num Status msgs Rcvd 552
Num Update Status Rcvd 0 Num Status Timeouts 0
Spicey#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/40 ms
Spicey#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
3.0.0.0/24 is subnetted, 1 subnets
C 3.1.3.0 is directly connected, Serial0
124.0.0.0/24 is subnetted, 1 subnets
C 124.124.124.0 is directly connected, Ethernet0
R 123.0.0.0/8 [120/1] via 3.1.3.2, 00:00:08, Serial0
Prasit Prasit#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 150(0x96,0x2460), dynamic,
broadcast,, status defined, active
Prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1
input pkts 87 output pkts 83 in bytes 8408
out bytes 8144 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 38 out bcast bytes 3464
pvc create time 01:34:29, last time pvc status changed 01:28:05
Prasit#show frame-relay lmi
LMI Statistics for interface Serial1 (Frame Relay DTE) LMI TYPE = CISCO
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0
Num Status Enq. Sent 569 Num Status msgs Rcvd 570
Num Update Status Rcvd 0 Num Status Timeouts 0
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Prasit#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
3.0.0.0/24 is subnetted, 1 subnets
C 3.1.3.0 is directly connected, Serial1
R 124.0.0.0/8 [120/1] via 3.1.3.1, 00:00:19, Serial1
123.0.0.0/24 is subnetted, 1 subnets
C 123.123.123.0 is directly connected, Ethernet0
Configuring Hub and Spoke Frame Relay In this example, the router learns which data-link connection identifiers (DLCIs) it uses from the Frame Relay switch and assigns them to the main interface. Then the router will Inverse ARP for the remote IP address.
Note: You will not be able to ping Prasit's serial IP address from Aton unless you explicitly add in Frame Relay maps on each end. If routing is configured correctly, traffic originating on the LANs should not have a problem. You will be able to ping if you use the Ethernet IP address as the source address in an extended ping.
When frame-relay inverse-arp is enabled, broadcast IP traffic will go out over the connection by default.
Network Diagram
Configurations
show Commands - show frame-relay map
- show frame-relay pvc
- ping < device name>
Spicey spicey#show frame-relay map
Serial0 (up): ip 3.1.3.2 dlci 140(0x8C,0x20C0), dynamic,
broadcast,, status defined, active
Serial0 (up): ip 3.1.3.3 dlci 130(0x82,0x2020), dynamic,
broadcast,, status defined, active
spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 2 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 130, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0
input pkts 32 output pkts 40 in bytes 3370
out bytes 3928 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 30 out bcast bytes 2888
pvc create time 00:15:46, last time pvc status changed 00:10:42
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0
input pkts 282 output pkts 291 in bytes 25070
out bytes 27876 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 223 out bcast bytes 20884
pvc create time 02:28:36, last time pvc status changed 02:25:14
spicey#
spicey#ping 3.1.3.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
spicey#ping 3.1.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
Prasit prasit#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 150(0x96,0x2460), dynamic,
broadcast,, status defined, active
prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1
input pkts 311 output pkts 233 in bytes 28562
out bytes 22648 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 162 out bcast bytes 15748
pvc create time 02:31:39, last time pvc status changed 02:25:14
prasit#ping 3.1.3.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
prasit#ping 3.1.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.3, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Aton aton#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 160(0xA0,0x2800), dynamic,
broadcast,, status defined, active
aton#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 160, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1
input pkts 35 output pkts 32 in bytes 3758
out bytes 3366 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 27 out bcast bytes 2846
pvc create time 00:10:53, last time pvc status changed 00:10:53
aton#ping 3.1.3.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
aton#ping 3.1.3.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Connecting from Spoke to Spoke You cannot ping from one spoke to another spoke in a hub and spoke configuration using multipoint interfaces because there is no mapping for the other spokes' IP addresses. Only the hub's address is learned via the Inverse Address Resolution Protocol (IARP). If you configure a static map using the frame-relay map command for the IP address of a remote spoke to use the local data link connection identifier (DLCI), you can ping the addresses of other spokes.
Configurations
show Commands - show frame-relay map
- ping < device name>
- show running-config
Prasit
prasit#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 150(0x96,0x2460), dynamic,
broadcast,, status defined, active
Serial1 (up): ip 3.1.3.3 dlci 150(0x96,0x2460), static,
CISCO, status defined, active
prasit#ping 3.1.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/70/80 ms
prasit#ping 122.122.122.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 122.122.122.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/67/76 ms
Aton
aton#show running-config
interface Ethernet0
ip address 122.122.122.1 255.255.255.0
!
interface Serial1
ip address 3.1.3.3 255.255.255.0
no ip directed-broadcast
encapsulation frame-relay
frame-relay map ip 3.1.3.2 160
frame-relay interface-dlci 160
aton#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 160(0xA0,0x2800), dynamic,
broadcast,, status defined, active
Serial1 (up): ip 3.1.3.2 dlci 160(0xA0,0x2800), static,
CISCO, status defined, active
aton#ping 3.1.3.2
Type escape sequence to abort
Sending 5, 100-byte ICMP Echos to 3.1.3.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/68/68 ms
aton#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/67/80 ms
Configuring Frame Relay Subinterfaces Frame Relay subinterfaces provide a mechanism for supporting partially meshed Frame Relay networks. Most protocols assume transitivity on a logical network; that is, if station A can talk to station B, and station B can talk to station C, then station A should be able to talk to station C directly. Transitivity is true on LANs, but not on Frame Relay networks unless A is directly connected to C.
Additionally, certain protocols, such as AppleTalk and transparent bridging, cannot be supported on partially meshed networks because they require "split horizon" in which a packet received on an interface cannot be transmitted out the same interface even if the packet is received and transmitted on different virtual circuits.
Configuring Frame Relay subinterfaces ensures that a single physical interface is treated as multiple virtual interfaces. This capability allows us to overcome split horizon rules. Packets received on one virtual interface can now be forwarded out another virtual interface, even if they are configured on the same physical interface.
Subinterfaces address the limitations of Frame Relay networks by providing a way to subdivide a partially meshed Frame Relay network into a number of smaller, fully meshed (or point-to-point) subnetworks. Each subnetwork is assigned its own network number and appears to the protocols as if it is reachable through a separate interface. (Note that point-to-point subinterfaces can be unnumbered for use with IP, reducing the addressing burden that might otherwise result).
Point-to-Point Subinterfaces Network Diagram
Configuration
show Commands - show frame-relay map
- show frame-relay pvc
Spicey Spicey#show frame-relay map
Serial0.1 (up): point-to-point dlci, dlci 140(0x8C,0x20C0), broadcast
status defined, active
Spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0.1
input pkts 193 output pkts 175 in bytes 20450
out bytes 16340 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 50 out bcast bytes 3786
pvc create time 01:11:27, last time pvc status changed 00:42:32
Spicey#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Prasit Prasit#show frame-relay map
Serial1.1 (up): point-to-point dlci, dlci 150(0x96,0x2460), broadcast
status defined, active
Prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
Serial1.1
input pkts 74 output pkts 89 in bytes 7210
out bytes 10963 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 24 out bcast bytes 4203
pvc create time 00:12:25, last time pvc status changed 00:12:25
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Hub and Spoke Subinterfaces The following hub and spoke sample configuration shows two point-to-point subinterfaces and uses dynamic address resolution on one remote site. Each subinterface is provided with an individual protocol address and subnetmask, and the interface-dlci command associates the subinterface with a specified data-link connection identifier (DLCI). Addresses of remote destinations for each point-to-point subinterface are not resolved since they are point-to-point and traffic must be sent to the peer at the other end. The remote end (Aton) uses Inverse ARP for its mapping and the main hub responds accordingly with the IP address of the subinterface. This occurs because Frame Relay Inverse ARP is on by default for multipoint interfaces.
Network Diagram
Configurations
show Commands - show frame-relay map
- show frame-relay pvc
Spicey Spicey#show frame-relay map
Serial0.2 (up): point-to-point dlci, dlci 130(0x82,0x2020), broadcast
status defined, active
Serial0.1 (up): point-to-point dlci, dlci 140(0x8C,0x20C0), broadcast
status defined, active
Spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 2 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 130, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0.2
input pkts 11 output pkts 22 in bytes 1080
out bytes 5128 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 17 out bcast bytes 4608
pvc create time 00:06:36, last time pvc status changed 00:06:36
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0.1
input pkts 33 output pkts 28 in bytes 3967
out bytes 5445 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 17 out bcast bytes 4608
pvc create time 00:06:38, last time pvc status changed 00:06:38
Spicey#ping 122.122.122.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 122.122.122.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
Spicey#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Prasit Prasit#show frame-relay map
Serial1.1 (up): point-to-point dlci, dlci 150(0x96,0x2460), broadcast
status defined, active
Prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
Serial1.1
input pkts 45 output pkts 48 in bytes 8632
out bytes 6661 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 31 out bcast bytes 5573
pvc create time 00:12:16, last time pvc status changed 00:06:23
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Aton Aton#show frame-relay map
Serial1 (up): ip 3.1.3.1 dlci 160(0xA0,0x2800), dynamic,
broadcast,, status defined, active
Aton#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 160, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1
input pkts 699 output pkts 634 in bytes 81290
out bytes 67008 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 528 out bcast bytes 56074
pvc create time 05:46:14, last time pvc status changed 00:05:57
Aton#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Configuring Dynamic and Static Mapping for Multipoint Subinterfaces Dynamic address mapping uses Frame Relay Inverse ARP to request the next hop protocol address for a specific connection, given a data-link connection identifier (DLCI). Responses to Inverse ARP requests are entered in an address-to-DLCI mapping table on the router or access server; the table is then used to supply the next hop protocol address or the DLCI for outgoing traffic.
Since the physical interface is now configured as multiple subinterfaces, you must provide information that distinguishes a subinterface from the physical interface and associates a specific subinterface with a specific DLCI.
Inverse ARP is enabled by default for all protocols it supports, but can be disabled for specific protocol-DLCI pairs. As a result, you can use dynamic mapping for some protocols and static mapping for other protocols on the same DLCI. You can explicitly disable Inverse ARP for a protocol-DLCI pair if you know the protocol is not supported on the other end of the connection. Because Inverse ARP is enabled by default for all protocols that it supports, no additional command is required to configure dynamic address mapping on a subinterface.
A static map links a specified next hop protocol address to a specified DLCI. Static mapping removes the need for Inverse ARP requests; when you supply a static map, Inverse ARP is automatically disabled for the specified protocol on the specified DLCI. You must use static mapping if the router at the other end either does not support Inverse ARP at all or does not support Inverse ARP for a specific protocol that you want to use over Frame Relay.
Network Diagram We've already seen how to configure a Cisco router to do Inverse ARP. The following example shows how to configure static maps in case you need them for multipoint interfaces or subinterfaces:
Configurations
debug and show Commands - show frame-relay map>
- show frame-relay pvc
Aton Aton#show frame-relay map
Serial1.1 (up): ip 4.0.1.1 dlci 160(0xA0,0x2800), static, broadcast,
CISCO, status defined, active
Aton#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 160, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
Serial1.1
input pkts 16 output pkts 9 in bytes 3342
out bytes 450 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 9 out bcast bytes 450
pvc create time 00:10:02, last time pvc status changed 00:10:02
Aton#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
Spicey Spicey#show frame-relay map
Serial0 (up): ip 4.0.1.2 dlci 140(0x8C,0x20C0), static, broadcast,
CISCO, status defined, active
Serial0 (up): ip 4.0.1.3 dlci 130(0x82,0x2020), static, broadcast,
CISCO, status defined, active
Spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 2 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 130, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0
input pkts 9 output pkts 48 in bytes 434
out bytes 11045 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 48 out bcast bytes 11045
pvc create time 00:36:25, last time pvc status changed 00:36:15
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0
input pkts 17 output pkts 26 in bytes 1390
out bytes 4195 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 16 out bcast bytes 3155
pvc create time 00:08:39, last time pvc status changed 00:08:39
Spicey#ping 122.122.122.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 122.122.122.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/40 ms
Spicey#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36
Prasit Prasit#show frame-relay map
Serial1.1 (up): ip 4.0.1.1 dlci 150(0x96,0x2460), static,
broadcast,
CISCO, status defined, active
Prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1.1
input pkts 28 output pkts 19 in bytes 4753
out bytes 1490 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 9 out bcast bytes 450
pvc create time 00:11:00, last time pvc status changed 00:11:00
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
For more information on these commands, please see Frame Relay Commands.
Configuring IP Unnumbered Frame Relay If you do not have the IP address space to use many subinterfaces, you can use IP unnumbered on each subinterface. If this is the case, you need to use static routes or dynamic routing so that your traffic is routed as usual, and you must use point-to-point subinterfaces.
Network Diagram The example below illustrates this:
Configurations
show Commands - show frame-relay map
- show frame-relay pvc
Spicey Spicey#show frame-relay map
Serial0.1 (up): point-to-point dlci, dlci 140(0x8C,0x20C0), broadcast
status defined, active
Spicey#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 140, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
Serial0.1
input pkts 23 output pkts 24 in bytes 3391
out bytes 4952 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 14 out bcast bytes 3912
pvc create time 00:04:47, last time pvc status changed 00:04:47
Spicey#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
124.0.0.0/24 is subnetted, 1 subnets
C 124.124.124.0 is directly connected, Ethernet0v 123.0.0.0/8 is variably subnetted, 2 subnets, 2 masksv I 123.0.0.0/8 [100/8576] via 123.123.123.1, 00:01:11, Serial0.1
I 123.123.123.0/32 [100/8576] via 123.123.123.1, 00:01:11,
Serial0.1
Spicey#ping 123.123.123.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 123.123.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/36 ms
Prasit Prasit#show frame-relay map
Serial1.1 (up): point-to-point dlci, dlci 150(0x96,0x2460), broadcast
status defined, active
Prasit#show frame-relay pvc
PVC Statistics for interface Serial1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 150, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
Serial1.1
input pkts 24 output pkts 52 in bytes 4952
out bytes 10892 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 41 out bcast bytes 9788
pvc create time 00:10:54, last time pvc status changed 00:03:51
Prasit#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
124.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
I 124.0.0.0/8 [100/8576] via 124.124.124.1, 00:00:18, Serial1.1
I 124.124.124.0/32 [100/8576] via 124.124.124.1, 00:00:18,
Serial1.1
123.0.0.0/24 is subnetted, 1 subnets
C 123.123.123.0 is directly connected, Ethernet0
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/120/436 ms
Frame Relay Backup over ISDN You may want to back up Frame Relay circuits using ISDN. There are several ways to do this. The first, and probably the best, is to use floating static routes that route traffic to a Basic Rate Interface (BRI) IP address and use an appropriate routing metric. You can also use a backup interface on the main interface or on a per-data-link connection identifier (DLCI) basis. It may not help much to back up the main interface because you could lose permanent virtual circuits (PVCs) without the main interface going down. Remember, the protocol is being exchanged with the local Frame Relay switch, not the remote router.
Configurations
show Commands To verify if the ISDN is working, use the following debug commands. Before issuing debug commands, please see Important Information on Debug Commands.
- debug isdn q931
- debug ppp neg
- debug ppp auth
Try to make an ISDN call from the calling side to the central side without the backup commands. If this is successful, add the backup commands to the calling side.
Note: To test the backup, do not use the shutdown command on the serial interface but emulate a real serial line problem by pulling out the cable from the serial line.
Network Diagram
Configurations
show Commands - show frame-relay map
- show ip route
- show isdn history
- show isdn status
- show interface bri 0
- how isdn active
Spicey Spicey#show frame-relay map
Serial0.2 (up): point-to-point dlci, dlci 130(0x82,0x2020), broadcast
status defined, active
Serial0.1 (up): point-to-point dlci, dlci 140(0x8C,0x20C0), broadcast
status defined, active
Spicey#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
3.0.0.0/24 is subnetted, 2 subnets C
3.1.3.0 is directly connected, Serial0.2 C
3.1.6.0 is directly connected, BRI0
4.0.0.0/24 is subnetted, 1 subnets C
4.0.1.0 is directly connected, Serial0.1
124.0.0.0/24 is subnetted, 1 subnets C
124.124.124.0 is directly connected, Ethernet0
123.0.0.0/8 is variably subnetted, 2 subnets, 2 masks I
123.0.0.0/8 [100/8576] via 4.0.1.2, 00:00:00, Serial0.1 S
123.123.123.0/24 [250/0] via 3.1.6.2 I
122.0.0.0/8 [100/8576] via 3.1.3.3, 00:00:37, Serial0.2
Spicey#
*Mar 1 00:59:12.527: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up
*Mar 1 00:59:13.983: %LINEPROTO-5-UPDOWN: Line protocol on Interface
BRI0:1, changed state to up
*Mar 1 00:59:18.547: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 6105 Prasit
Spicey#show isdn history
-------------------------------------------------------------------------------- ISDN CALL HISTORY
-------------------------------------------------------------------------------- Call History contains all active calls, and a maximum of 100 inactive calls.
Inactive call data will be retained for a maximum of 15 minutes.
-------------------------------------------------------------------------------- Call Calling Called Remote Seconds Seconds Seconds
Charges
Type Number Number Name Used Left Idle Units/Currency
-------------------------------------------------------------------------------- In 6105 6106 Prasit 31 90 29
-------------------------------------------------------------------------------- Spicey#
*Mar 1 01:01:14.547: %ISDN-6-DISCONNECT: Interface BRI0:1 disconnected
from 6105 Prasit, call lasted 122 seconds
*Mar 1 01:01:14.663: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down
*Mar 1 01:01:15.663: %LINEPROTO-5-UPDOWN: Line protocol on Interface
BRI0:1, changed state to down
Prasit Prasit#show frame-relay map
Serial1.1 (up): point-to-point dlci, dlci 150(0x96,0x2460), broadcast
status defined, active
Prasit#ping 124.124.124.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 124.124.124.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/36/40 ms
Prasit#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
I 3.0.0.0/8 [100/10476] via 4.0.1.1, 00:00:55, Serial1.1
4.0.0.0/24 is subnetted, 1 subnets
C 4.0.1.0 is directly connected, Serial1.1
124.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
S 124.124.124.0/24 [250/0] via 3.1.6.1
I 124.0.0.0/8 [100/8576] via 4.0.1.1, 00:00:55, Serial1.1
123.0.0.0/24 is subnetted, 1 subnets
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