You should configure two other commands on your BRI interface: dialer load-threshold
and dialer idle-timeout. The dialer load-threshold command is used in conjunction
with the ppp multilink command for multilink PPP (MPPP).
The dialer load-threshold command tells the BRI interface when to bring up the second
B channel. The value specified is from 1–255, where 255 tells the BRI to bring up the second B
channel only when the first channel is 100 percent loaded. The second option for that command
Dial-on-Demand Routing (DDR) 847
is in, out, or either. This calculates the actual load on the interface either on outbound traffic,
inbound traffic, or either inbound or outbound traffic. The default is outbound.
The dialer idle-timeout command specifies the number of seconds to wait for interesting
traffic before a call is disconnected. The default is 120 seconds.
RouterA(config-if)#dialer load-threshold 127 either
RouterA(config-if)#dialer idle-timeout 180
The dialer load-threshold 127 command tells the BRI interface to bring up the second B
channel if either the inbound or outbound traffic load is 50 percent. The dialer idle-timeout
180 command changes the default disconnect time from 120 to 180 seconds.
MPPP allows load-balancing between two or more B channels on a BRI or PRI interface. It is
non-vendor-specific and provides packet fragmentation and reassembly, along with sequencing
and load-calculating. Cisco’s MPPP is based on RFC 1990, which is referred to as PPP Multilink
Protocol (MP). The configuration would then look like this:
RouterA(config)#int BRI0
RouterA(config-if)#dialer load-threshold 127 either
RouterA(config-if)#dialer idle-timeout 180
RouterA(config-if)#ppp multilink
Not a tough configuration, but you should use it nonetheless. The ppp multilink command will
fragment packets and send them over both lines, which provides a load-balancing effect on the data
being sent over the link. You can verify that the Multilink Protocol is working by using the show ppp
multilink command.