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Frame Relay

Permanent virtual circuit (PVC) – gives appearance all end points are connected together
data link connection identifier (DLCI) – Numbers locally assigned for each originating circuit
local management interface (LMI) – language between CPE and ISP router
network-to-network interface (NNI) – configuration between ISP routers that provide the frame relay network
local access rate / committed information rate (CIR) – local access rate is physical connection speed (i.e. 1.544 T1), CIR is what ISP guarantees you (i.e. 128kbps), bw that is split out for PVCs

Hub and spoke lab (R3, R4 have to route through R2 to get to R2):
R1 ——– R2
|—- R3
|—- R4

R1
conf t
int s0/0
encapsulation frame-relay
ip address 10.1.1.1 255.255.255.0
no shut
show frame-relay lmi (check status sent/received)
show int s0/0 (LMI DLCI 1023, used for ISP to send info)

R2
int s0/0
encapsulation frame-relay
ip address 10.1.1.2 255.255.255.0
no shut
show frame-relay map <== 3 states
#active – local & remote connection working
#inactive – local connection working, remote is not
#deleted – local connect not working

show frame-relay pvc (shows status, pkts sent/rcvd, dlci)
# turn off inverse arp, if there are too many dlcis shown (CCIE lab)
# use subinterfaces for multiple p2p or p2m links, p2p is preferred)
R1
int s0/0
no frame-relay inverse-arp (prevents autodiscovery dlci…pertinent to ccie lab)
no arp frame-relay (prevents others from autodiscovering your dlci)
no ip address
end
clear frame-relay inarp (clear caches)
conf t
int s0/0.1 point-to-point (encap frame-relay has to already be ON on main interface)
ip address 10.1.1.1 255.255.255.0
frame-relay interfcace-dlci 102 (hard code dlci 102)
exit
# point to mulitpoint
int s0/0.2 multipoint
ip address 172.16.1.1 255.255.255.0
frame-relay map ip 172.16.1.2 103 broadcast (dlci 103 to remote router, broadcast allows routing protocols updates)
frame-relay map ip 172.16.1.3 104 broadcast (dlci 104 to other multilink)
show ip int brief
sh frame-relay map

R3
conf t
int s0/0
encapsulation frame-relay
no frame inverse-arp
no arp frame
ip address 172.16.1.2 255.255.255.0
frame map ip 172.16.1.1 301 broadcast
no shutdown

R4
conf t
int s0/0
encapsulation frame-relay
no frame inverse-arp
no arp frame
frame map ip 172.16.1.1 401 broadcast
no shut
show frame map

# now create mappings to get to R2, R3
frame map ip 172.16.1.2 401 broadcast

R3
conf t
int s0/0
frame map ip 172.16.1.3 301 broadcast
ping 172.16.1.1
show ip route (with eigrp networks would be advertised from R1 s0/0)
# Split horizon will prevent network advertisements going back the subinterfaces it came in from. R3 cannot see R4's LAN networks

R1
conf t
int s0/0.2
no ip split-horizon eigrp 1 (allow split horizon for eigrp AS 1, to allow eigrp adverts)

R4
# check if ip routes are now advertised
show ip route

## Frame Relay traffic shaping
CIR (committed information rate, i.e. 64kbps, guaranteed)
Tc (timing interval in 1/8s)
CIR/Tc = Bc (committed burst) = 64000/8 = 8000 bp per Tc
# If you don’t use all of your traffic, you can bank non-used bandwidth depending on ISP
Be (Excess Burst), the extra bw can have DE (discard eligible) added to FR headers

BECN – backwards explicit congestion notification (ISP tells your router to slow down, if congested)
FECN – forwards explicit congestion notification (SP adds header to target router to forward packet back to source router to slow down)
– routers drop both becn, fecn by default

1. create map-class and define parameters
2. interface configuration “frame traffic-shaping”
3. apply map-class to interface or pvc

R1 (R3 only has 28kbps)
conf t
map-class frame-relay SLOW
frame-relay adaptive-shaping becn
frame-relay mincir 24400 (do not go below 24kbps)
frame-relay cir 28800
frame-relay bc 3600 (28800/8 = 3600)
frame-relay be 200 (negotiated bonus bits from ISP)
# other options
frame-relay traffice-rate 28800 30000

show traffic-shape (nothing yet)
conf t
int s0/0
frame-relay traffic-shaping
int s0/0.1 (goes to R2)
frame-relay class SLOW (applied to interface, all subints will be affected too)
# Alternative to apply to specific dlci
frame-relay interface-dlci 102
frame-relay class SLOW
show traffic-shape

Categories: Cisco, Routing
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