Title: Configuring Frame Relay
1Configuring Frame Relay
2Frame Relay
Frame relay specifies the interface between the
DTE (FRAD) and the DCE (FRND) but does not
specify the connection within the Frame Relay
cloud.
FRAD
FRAD
Access Link
Access Link
FRND
FRND
Access link may be many types of access service
carriers provide including SW56, T1, FT1, etc.
3Frame Relay Frame
Frame Relay Address
Data
FCS
flag
flag
Address field (2 octets) First 10 bits Data
Link Connection Identifier (DLCI) Last 3 bits
Congestion Control Forward Explicit Congestion
Notification (FECN) Backward Explicit
Congestion Notification (BECN) Discard
Eligibility (DE) Data many types of data
including IP packet Flag mark beginning and
end of frame
4Frame-Relay Encapsulation
- Two types of Frame-Relay encapsulation
- Cisco
- Default used to connect two Cisco devices
- Proprietary
- IETF
- Encapsulation frame-relay ietf
- Used to connect to non-Cisco devices
- Standard
5Virtual Circuits
Permanent Virtual Circuits (PVC) established by
administrator and last until removed. Switched
Virtual Circuits (SVC) established by a
call setup frame and last until transmission ends.
6Frame-Relay DLCIs
- DLCI is a value between 16 and 1007
- Router can support multiple VCs on a single
serial interface using subinterfaces - You would obtain the DLCI values from the WAN
provider
7(No Transcript)
8Local Management Interface (LMI)
- LMI are extensions to the Frame Relay standard
that allow Frame Relay devices to communicate
with one another - Simplifies Frame Relay configuration since DTEs
can automatically detect DLCI values - Three types
- Cisco (default), ansi, q933a
- After IOS 11.2 LMI type is autosensed
RouterA(config-if)frame-relay lmi-type ansi
9LMI Extensions
- Common extensions
- Virtual circuit status messages allow router to
determine what PVCs are available and to
determine the operational status of PVCs the
router knows about - Router can transmit keepalive frames to ensure
the PVC stays up
10LMI Extensions
- Optional extensions
- Multicasting
- Global addressing gives DLCIs global rather than
local significance - Simple flow control
11Inverse-ARP
- Inverse-ARP is used by routers to build frame
relay maps by requesting the IP addresses
associated with each DLCI - Inverse ARP messages are exchanged every 60
seconds between routers on a PVC
Route Table Frame
Relay Map Network Next Hop
Next Hop DLCI 10.0.0.0 172.16.1.2
172.16.1.2 100
12Frame Relay Map
- A routers frame relay map matches DLCIs with
specific interfaces - The map identifies DLCIs with network addresses
R3show frame-relay map Serial0.1 (up) ip
129.130.32.1, dlci 301(0x12D,0x48D0),
broadcast status defined, active
13Configuring the Frame Relay Map Manually
- Without inverse-ARP the frame relay map must be
built manually
RouterA(config-if)frame-relay map ip
172.16.30.17 16 ietf broadcast 16 DLCI Ietf
frame relay encapsulation type Broadcast send
broadcasts
14Point-to-Point Connections
- A subinterface on one router is connected to one
interface or subinterface on another router - Both are in the same subnet
- Broadcasts are not forwarded
10.0.0.2
10.0.0.1
15Multipoint Connections
- A subinterface on one router is connected to
subinterfaces on multiple other routers - All are in the same subnet
- Broadcasts are forwarded to all routers and split
horizon is in effect
10.0.0.4
DLCI1
10.0.0.1
10.0.0.2
DLCI2
10.0.0.3
16Frame Relay Configurations
- Three possible Frame Relay networks
- Full Mesh VCs between every pair of routers
- Partial Mesh Some routers dont have VCs
between them - Hybrid Part of the network is full mesh and
part is partial mesh
17Full Mesh Networks
A
199.1.1.1
s0
s0
s0
199.1.1.3
199.1.1.2
18Configuration of Router A
RouterA(config)int serial 0 RouterA(config-if)en
capsulation frame-relay RouterA(config-if)ip
address 199.1.1.1 255.255.255.0
Default settings used LMI type is automatically
sensed Encapsulation is cisco PVC DLCIs are
learned via LMI Inverse ARP is enabled and used
to build map
19Partial Mesh Network with Point-to-Point
Connections
A
DLCI 51
s0
140.1.3.0/24
140.1.1.0/24
140.1.2.0/24
s0
s0
s0
B
DLCI 52
DLCI 54
DLCI 53
20Configuration of Router A
RouterA(config)int serial 0 RouterA(config-if)en
capsulation frame-relay RouterA(config-if)int
serial 0.1 point-to-point RouterA(config-if)ip
address 140.1.1.1 255.255.255.0 RouterA(config-if)
frame-relay interface-dlci 52 RouterA(config-if)
int serial 0.2 point-to-point RouterA(config-if)i
p address 140.1.2.1 255.255.255.0 RouterA(config-i
f)frame-relay interface-dlci 53
21Configuration of Router A
RouterA(config-if)int serial 0.2
point-to-point RouterA(config-if)ip address
140.1.3.1 255.255.255.0 RouterA(config-if)frame-r
elay interface-dlci 54
22Configuration of Router B
RouterB(config)int serial 0 RouterB(config-if)en
capsulation frame-relay RouterB(config-if)int
serial 0.1 point-to-point RouterB(config-if)ip
address 140.1.1.2 255.255.255.0 RouterB(config-if)
frame-relay interface-dlci 51
23Partial Mesh Network with Multipoint Connections
DLCI 51
A
s0
140.1.1.0/24
140.1.1.0/24
140.1.1.0/24
s0
s0
s0
B
DLCI 52
DLCI 54
DLCI 53
24Configuration of Router A
RouterA(config)int serial 0 RouterA(config-if)en
capsulation frame-relay RouterA(config-if)int
serial 0.1 multipoint RouterA(config-if)ip
address 140.1.1.1 255.255.255.0 RouterA(config-if)
frame-relay interface-dlci 52 RouterA(config-if)
frame-relay interface-dlci 53 RouterA(config-if)f
rame-relay interface-dlci 54
25Configuration of Router B
RouterA(config)int serial 0 RouterA(config-if)en
capsulation frame-relay RouterA(config-if)int
serial 0.1 point-to-point RouterA(config-if)ip
address 140.1.1.2 255.255.255.0 RouterA(config-if)
frame-relay interface-dlci 51
26Hybrid Networks
DLCI 51
A
s0
140.1.2.0/24
140.1.1.0/24
140.1.1.0/24
s0
s0
s0
B
DLCI 54
DLCI 52
DLCI 53
27Router A Configuration
RouterA(config)int serial 0 RouterA(config-if)en
cap frame-relay RouterA(config-if)int serial 0.1
multipoint RouterA(config-if)ip address
140.1.1.1 255.255.255.0 RouterA(config-if)frame-r
elay interface-dlci 52 RouterA(config-if)frame-re
lay interface-dlci 53 RouterA(config-if)int
serial 0.2 point-to-point RouterA(config-if)ip
address 140.1.2.1 255.255.255.0 RouterA(config-if)
frame-relay interface-dlci 54
28Router B Configuration
RouterB(config)int serial 0 RouterB(config-if)en
cap frame-relay RouterB(config-if)int serial 0.1
multipoint RouterB(config-if)ip address
140.1.1.2 255.255.255.0 RouterB(config-if)
frame-relay map ip 140.1.1.1 51
b RouterB(config-if) frame-relay map ip
140.1.1.3 53 b
29Non-Broadcast MultiAccess (NBMA) Networks
- NBMA networks are those that allow multiple nodes
to access the network but do not support
broadcasts - Broadcast (like routing updates) packets must be
transmitted to each node individually in NBMA
networks
30Broadcasts
- Since Frame Relay doesnt allow broadcasts,
routers must transmit updates across every VC
that you tell it to - On a router with 100s of VCs this can cause
problems - Routers use different queues for broadcast
packets and administrator can limit the amount of
bandwidth devoted to broadcasts
31Split Horizon
- Since multiple VCs are connected to a single
physical interface Split Horizon can cause
problems - Router doesnt advertise routes out an interface
from which it learned them - Split horizon is applied to subinterfaces as if
they were separate physical interfaces - Routes learned on one subinterface are advertised
out other interfaces
32Split Horizon in Frame-Relay
DLCI 51
A
s0
140.1.1.0/24
140.1.1.0/24
140.1.1.0/24
s0
s0
s0
B
DLCI 52
DLCI 54
DLCI 53
33IOS Commands to Know
- Encapsulation frame-relay
- Frame-relay map
- Frame-relay interface-dlci
34IOS Commands to Know
- Show interfaces serial
- Displays information about the multicast DLCI and
DLCIs used on the Frame Relay configured serial
interface, and the LMI DLCI used - Show frame-relay PVC
- Displays the status of each configured connection
as well as traffic statistics. This command is
useful for viewing the number of BECN and FECN
frames received by the router.
35IOS Commands to Know
- Show frame-relay map
- Displays the network-layer address and associated
DLCI for each remote destination - Show frame-relay lmi
- Displays LMI traffic statistics.
36Configuring DLCIs
Used with subinterfaces RouterA(config)interfa
ce serial 0.1 multipoint RouterA(config-if)frame-
relay interface-dlci 100 RouterA(config-if)interf
ace serial 0.2 multipoint RouterA(config-if)frame
-relay interface-dlci 200