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HDLC and PPP

# Cisco HDLC (enhanced HDLC)
– added keepalives
– added SLARP, gets IP address
– added STAC compression
– performance increases (7-12 byte header)

show controllers serial0/1
conf t
int s0/1
clock rate 64000
no shut
show interfaces serial 0/1
compress stac <== do on both sides of DCE, DTE

debug serial interface <== watches keepalives, 3 keepalives have to fail before link declared down

# PPP (data link protocol, use multilink to load balance)
# only 1 router configuration shown, must configure for each end point with same
int s0/0
encapsulation ppp
int s0/1
encapsulation ppp
exit
interface multilink 1
ip address 172.216.1.1 255.255.255.252
encapsulation ppp
multilink-group 1
int s0/0
multilink-group 1
int s0/1
multilink-group 1
show ppp multilink <== show load balancing
# authentication
conf t
username router2 password pass
int s0/0
ppp authentication chap
# On router2
conf t
username router1 password pass
int s0/0
ppp authentication chap
debug ppp authentication
# compression
conf t
int multilink 1
compress [mppc|predictor|stac] <== compresses pkts, mppc for MSFT clients, predictor (more memory, less cpu), stac (more cpu)
ip tcp header-compression <== only compress header
# options
ppp reliable-link <== error correction, L2
ppp quality 75 <== watch connection, see other side is received, if 75% pkts not received, drop line

debug ppp negotiation

# configuration on modems
conf t
int loopback 3
ip address 1.1.1.1 255.255.255.255
show line <== see aux port
conf t
line 129
transport input all
speed 38400
modem inout <== allow inbound/outbound calls
modem autoconfigure type usr_sportster <== usr_sportser is specific type here, can use "discovery" as well
show modecap <== show database of modems
show modemcap usr_sportser <== show configuration for this modem type
int async 129
encapsulation ppp
ppp authentication chap
async mode interactive <== allows for access to or through router, "dedicated" would only allow through the router
ip address 192.168.1.10 255.255.255.0
peer default ip address 192.168.1.11 <== assign IP to dial in
peer default ip address pool emergency <== assign IP pool to dial in
ip local pool emergency 192.168.1.11 192.168.1.12 <== give out 2 IPs
int async 129
dialer in-band <== sends digits on same line for outbound calls
dialer idle-timeout 60 <== disconnect if idle 60s

Categories: Cisco, Routing
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