Frame Relay-Brief Introduction and basic configuration

Frame Relay is becoming increasingly popular today, but it has been widely used in past designs.

This blog post briefly summarizes some concepts of FR from the second layer.

Before introducing frame relay, let's first understand the differences between broadcast media and non-broadcast media:

Broadcast media): Ethernet, token-ring, FDDI

Features:

• The source can call all connected (Layer 2) Destination addresses at the same time.
• Simplified layer-3 to layer-2 Parsing

Non-broadcast multi access (nbma): Frame relay, ISDN, and ATM etc.

Features:

• The source cannot communicate with all the destination addresses connected to Layer 2 at the same time.
• Layer-3 broadcast is implemented through layer-2 repeated Unicast (pseudo-broadcast)

========= Comparison Between Layer-3 and layer-2 address resolution ======

Layer-3 Address Resolution of broadcast media: Remote L2 MAC address and remote L3 Address binding

-IPv4 adress Resolution Protocol (ARP)

• Broadcast Request-who knows the MAC address of 1.1.1.1
• Unicast reply-my Mac is ABCD. ABCD. ABCD

Layer-3 Address Resolution of broadcast media: Remote or local L2 MAC address and remote L3 Address binding

• Local fr dlci and remote IPv4 address binding
• Remote ISDN phone and original power IPX Address binding

-Reverse ARP parses the remote layer-3 address to the local layer-2 address

-Only directly connected devices can be parsed.

Nbma port type:

Multi-Point interface-connection to multiple L2 links & resolution from L3 to L2 (fr & ATM Main Interface)

Single point interface (spof)-connects to a layer-2 link and does not require layer-3 to layer-2 Resolution (PPP link, fr P2P subinterface)

==============================================

1. fr Brief Introduction

When nbma is applied, there are potential layer-3 to layer-2 Resolution problems.

Dlci-data link connection identifier (digital link identifier)

• L2 addressing
• Dlci effective locally

Lm-local Management Interface

• DTE or DCE Communication
• Reporting the status of a virtual link

2. fr LMS Configuration Enable fr -Encapsulation frame-relay Type of LMS (self-active detection) -Frame-relay lm-type [Cisco | ANSI | q933a]-show frame-relay LMIS Verify the status of the virtual connection VC -Show frame-relay PVC Status type: -Active (e2e is good, at least router to switch is OK)-inactive (a problem occurs in the middle)-Deleted, configuration error, etc.)-static (LMIS is disabled, used for back to back fr)
3. fr Address Resolution -Multi-Point Port requires layer-3 to layer-2 Resolution: Which dlci is required to send packets to ip a. B. C. D? -Resolution type

• Dynamic parsing through reverse ARP request (inverse ARP)
• Static parsing by using the command frame-relay Map

-Verification: Sh frame-relay Map
======== Fr inverse ARP -When the protocol supported by FR is configured, reverse ARP is automatically enabled.-The request is sent on all links configured by the port.

• The reverse APR request can send disable-no frame-relay inverse ARP [Protocol] [dlci]
• The reply cannot be disable (this is a potential problem)

-Automatically include broadcast support
Fr static Mapping -Manually bind the local L2 address to the remote L3 address

• Frame-relay map [Protocol] [address] dlci [Broadcast]
• Same as static ARP Logic

-Static configuration overwrites dynamic configuration.-To support broadcasting, you must manually configure ========.
The auto-install and frame relay of the vro may introduce the following problems:-if there is no configuration file in NVRAM, the router detects the encapsulation mode of the ingress port and sends the address request Lan-dhcphdlc-slarpfr-BOOTP-after the address is configured, the router tries to get the configuration through TFTP.
Fr problems here are listed in Step 4:

1. Plugin Encapsulation
2. LMIS Learning Through dlci
3. Send BOOTP to all dlcis
4. If the request fails, the system automatically configures 0.0.0.0 mapping.

• This may damage the subsequent route configuration.
• The solution is save config and reload.

======================= The last point-to-point port to be mentioned
-A port does not need to be resolved from Layer 3 to Layer 2 on a layer 2 link, you only need to configure the Link number-frame-relay interface-dlci [dlci]-more inclined to point-to-point configuration (to avoid configuration problems above three layers)

==================== Cisco official documentation-basic configuration

An interface is by default a "multipoint" interface so,Frame-relay inverse-ARPIs 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 LR updates. the routers then inverse ARP for the remote IP address and create a mapping of local dlcis and their associated remote IP addresses.

Spicey

Spicey # show running-config building configuration... current configuration: 1705 bytes! Version 12.1 service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption! Hostname Spicey !!! Interface ethernet0 IP address 124.124.124.1 255.255.255.0! Interface serial0 IP address 3.1.3.1 255.255.255.0 encapsulation frame-relay interface-dlci 140 !! Router rip network 3.0.0.0 network 124.0.0.0! Line con 0 Exec-timeout 0 0 Transport input noneline aux 0 line vty 0 4 login! End

Prasit

Prasit #Show running-configBuilding configuration... current configuration: 1499 bytes! Version 12.1 service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption! Hostname prasit !!! Interface ethernet0 IP address 123.123.123.1 255.255.255.0 !! Interface serial1 IP address 3.1.3.2 255.255.255.0 encapsulation frame-relay interface-dlci 150 !! Router rip network 3.0.0.0 network 123.0.0.0 !!! Line con 0 Exec-timeout 0 0 Transport input noneline aux 0 line vty 0 4 login! End

Verify

• Show frame-relay Map

• Show frame-relay PVC

• Show frame-relay LMS

• Ping <Device Name>

• Show IP Route

Spicey#show frame-relay mapSerial0 (up): ip 3.1.3.2 dlci 140(0x8C,0x20C0), dynamic,              broadcast,, status defined, activeSpicey#show frame-relay pvcPVC 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            0DLCI = 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 01:28:28Spicey#show frame-relay lmiLMI 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 0Spicey#ping 123.123.123.1Type 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 msSpicey#show ip routeCodes: 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-ISinter 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 subnetsC       3.1.3.0 is directly connected, Serial0     124.0.0.0/24 is subnetted, 1 subnetsC       124.124.124.0 is directly connected, Ethernet0R    123.0.0.0/8 [120/1] via 3.1.3.2, 00:00:08, Serial0

Prasit#show frame-relay mapSerial1 (up): ip 3.1.3.1 dlci 150(0x96,0x2460), dynamic,              broadcast,, status defined, activePrasit#show frame-relay pvcPVC 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            0DLCI = 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 01:28:05Prasit#show frame-relay lmiLMI 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 0Prasit#ping 124.124.124.1Type 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 msPrasit#show ip routeCodes: 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-ISinter area       * - candidate default, U - per-user static route, o - ODR       P - periodic downloaded static routeGateway of last resort is not set     3.0.0.0/24 is subnetted, 1 subnetsC       3.1.3.0 is directly connected, Serial1R    124.0.0.0/8 [120/1] via 3.1.3.1, 00:00:19, Serial1     123.0.0.0/24 is subnetted, 1 subnetsC       123.123.123.0 is directly connected, Ethernet0

Exam materials: comprehensive guide to indexing and troubleshooting Frame Relay

Frame Relay-Brief Introduction and basic configuration