Clase 6. Frame Relay Configuration.pdf

REDES WAN

Tema 6. Frame Relay Basic Configuration Alberto Arellano A. Ing. Msc. [email protected] CCNA – CCNP - CCSP

Frame Relay Encapsulation Router(config-if)#encapsulation frame-relay {cisco | ietf}

 cisco - Default. 

Use this if connecting to another Cisco router.

 Ietf - Select this if connecting to a non-Cisco router. 

RFC 1490

Frame Relay LMI LMI is a set of signalling standards between routers and frame relay switches. Communication takes place between a router and the first frame relay switch it's connected to. Information about keepalives, global addressing, IP Multicast and the status of virtual circuits is commonly exchanged using LMI. There are three standards for LMI:  Using DLCI 0:  ANSI's T1.617 Annex D standard  ITU-T's Q.933 Annex A standard  Using DLCI 1023:  The "Gang of Four" standard, developed by Cisco, DEC, StrataCom and Nortel Router(config-if)#frame-relay lmi-type {ansi | cisco | q933a}

Minimum Frame Relay Configuration

R1(config)# interface serial 2/0

R1(config-if)# ip address 172.16.1.2 255.255.255.0 R1(config-if)# encapsulation frame-relay R1(config-if)# frame-relay lmi-type ansi R2(config)# interface serial 2/0

R2(config-if)# ip address 172.16.1.1 255.255.255.0 R2(config-if)# encapsulation frame-relay R2(config-if)# frame-relay lmi-type ansi

Minimum Frame Relay Configuration

 Cisco Router is now ready to act as a Frame-Relay DTE device. The following process occurs: 1. The interface is enabled. 2. The Frame-Relay switch announces the configured DLCI(s) to the router. 3. Inverse ARP is performed to map remote network layer addresses to the local DLCI(s). The routers can now ping each other!

Inverse ARP

R1# show frame-relay map Serial0 (up): ip 172.16.1.1 dlci 101, dynamic, broadcast, status defined, active

• •

dynamic refers to the router learning the IP address via Inverse ARP The DLCI 101 is configured on the Frame Relay Switch by the provider.

Inverse ARP Limitations

 Inverse ARP only resolves network addresses of remote FrameRelay connections that are directly connected.  Inverse ARP does not work with Hub-and-Spoke connections.  When using dynamic address mapping, Inverse ARP requests a nexthop protocol address for each active PVC.  Once the requesting router receives an Inverse ARP response, it updates its DLCI-to-Layer 3 address mapping table.  Dynamic address mapping is enabled by default for all protocols enabled on a physical interface.  If the Frame Relay environment supports LMI autosensing and Inverse ARP, dynamic address mapping takes place automatically.  Therefore, no static address mapping is required.

Configuring Frame Relay maps Router(config-if)#frame-relay map protocol protocol-address dlci [broadcast] [ietf | cisco]

 If the environment does not support LMI autosensing and Inverse ARP, a Frame Relay map must be manually configured.  Use the frame-relay map command to configure static address mapping.  Once a static map for a given DLCI is configured, Inverse ARP is disabled on that DLCI.  The broadcast keyword is commonly used with the frame-relay map command.  The broadcast keyword provides two functions.  

Forwards broadcasts when multicasting is not enabled. Simplifies the configuration of OSPF for nonbroadcast networks that use Frame Relay.

By default, cisco is the default encapsulation

Uses cisco encapsulation for this DLCI (not needed, default)

Remote IP Address

Local DLCI

Verifying Frame Relay interface configuration

 The show interfaces serial command displays information regarding the encapsulation and the status of Layer 1 and Layer 2.  It also displays information about the multicast DLCI, the DLCIs used on the Frame Relay-configured serial interface, and the DLCI used for the LMI signaling.

show frame-relay pvc

 The command show frame-relay pvc shows the status of all PVCs configured on the router.  This command is also useful for viewing the number of Backward Explicit Congestion Notification (BECN) and Forward Explicit Congestion Notification (FECN) packets received by the router.  If a single PVC is specified, only the status of that PVC is shown.

show frame-relay map show frame-relay lmi

Frame Relay Example

Frame Relay Example

Note: LMI Type Ansi configured by default

Configure Frame Relay Routers

Configure Frame Relay Routers

Verify PVC – R1

Verify PVC – R1

Verify Connectivity from R1

Configure OSPF Protocol

Configure OSPF Protocol

Configure OSPF Protocol

Verify Routing Table

Configure Switching Frame Relay

Configure Switching Frame Relay

Configure Switching Frame Relay

Configure PVCs on Frame Relay Switch

Configure Routers - DTE

Verify Status PVCs

Verify Status PVCs