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FRAME RELAY

Frame relay header size is 2 bytes

DLCI:-

To connect two DTEs, an FR service uses a virtual circuit (VC)between pairs of routers. Arouter can then send an FR frame with the appropriate (typically) 10-bitData Link Connection

Identifier (DLCI) header field that identifies each VC.

DLCI is a layer 2 address.10.bits are for DLCI.

LMI:Local Management Interface (LMI) messages manage the local access link between the router

and the Frame Relay switch. DTE side can send status inquiry to frame relay switch, switch

replies with the dlci no assigned to the VC.IT is the responsible for link establishment anddeleting.

It works as keep alive by default time is 10 sec.

There are three types of LMI:1) CISCO2) ANSI3) ITU

Frame relay payload compression:

Framerelay payload compression feature compress the bits of header of attached with the dataLZS algorithm assigns dynamic dictionary entries listed in binary strings.

There are three types of compression

1) Packet by packet(cisco proprietary)(uses LZS algorithm)2) FRF.9(IEEE standard)(LZS algorithm)3) Data stream(cisco proprietary)(LZS algorithm)

Command:Show compress

FRAMERELAY TOPOLOGIES:1) Hub and spoke topology

In which spokes are connected to single host, every spoke traffic is passed through that

host

2) Full mesh topologyIn which everyone is mapped with each other

FRAMERELAY CONNECTION TYPES:By default frame relay act as a non-broadcast multi-access network. Which cannot carry and

updates of protocols such as rip those protocols uses broadcast to send their periodic updates

If we want traffic could be travel on the link the broadcast word should be added

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Hub to spoke Spoke to hub

Never use keyword of broadcast with own ip mapping or with spoke to spoke mappingThere are two types of connections

1) PP(point to point)In point to point single host is connected at the end2) PMP(point to multipoint)In PMP more than one host is connected on a single network ID

FR Connection STATES:

1) ACTIVEBoth sides are working

2) INACTIVE:Other side has problem

3) DELETED:Own side problem

FR SUBINTERFACE:

Frame relay sub interfaces resolves the NBMA reachability issues such as

Split horizon:

Route is not send from that interface from it has been received

When we configure PP link it is disabled by defaultto disable this feature in PMP

Command:

No ip split horizon (under interface level)

AUTHENTICATION:

To configure authentication on frame relay we have to first go through these steps

1) Create PPP virtual templates on framerelay PP subinterfacePPP

/ \NCP(network control protocol) LCP(link control protocol)

/ | \

Authentication multilinking compression

/ \

PAP CHAP

VIRTUAL TEMPLATES:

All configurations are configured under this logical interface and then called to otherserial interfaces

MULTILINKING:

It is just like ether channel in which two links are combined and assigned a single ip

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COMPRESSION:

Data is compressed or decompressedPAP(password authentication protocol):

Its a clear text authentication means 64 bit authentication

CHAP(chake head authentication protocol)Its a md5 authentication most secure.it hashes its HOSTNAME and PASSWORD using

MD5 algorithm

RESTRICTIONS:

1) Always disable inverse ARP(address resolution protocol)which map ip against DLCIdynamically)

2) Never use the keyword of broadcast against own ip mapping3) Never use broadcast keyword against spoke to spoke mapping

COMANDS:

Sh framerelay pvc

[Important] Frame relay encapsulation could also be referred as RFC

1490/2427 means IETF in some books or during CCIE Exam.

Command:

Encapsulation frame relay IETFThis encapsulation is used where different vendors are working

NOTE:

If one side is configured with cisco and other side is configured with IETF the VC will be in deletestate.

RFC 1490/2427 ARE CALLED NLPID(network layer protocol ID)

CCIE Routing or Service Provider Exam Troubleshooting:

1) Inverse ARP is on2) Frame relay Map command is not used for other end3) Wrong DLCI are used4) There is no frame relay Switch in between two Hosts5) Broadcast keyword is missing towards HUB.6) Own Interface IP address Mapping is missing7) Authentication Mismatch8) Password Mismatch9) Hostnames are wrongly configured due to which ChAP authentication is not successful10)Wrong IP address is used while mapping with DLCI.