Serial Links bundling with MLPPP

Since a serial link have limitation when it comes to bandwidth, bundling multiple serial links into one link would be a good solution, so having a simple topology like the one below, we will configure a feature that allows us to combine serial links into one, here we have S1/0-3 between R1 which is the Server Router that we can consider as ISP and R2 which is the client router that will get IP address from R1

R1:
starting with creating a virtual interface that will have the IP address configured on it
# interface Multilink1
#ip address 12.0.0.1 255.255.255.0
# peer default ip address pool R1-IP
# ppp multilink
# ppp multilink group 1  

enabling ppp multilink and configuring group1 that we will associate the serial interfaces to it later

the IP address of the Client will be acquired from R1 and that is by using the command
#peer default ip address pool POOL-NAME
and # ip local pool R1-IP 12.0.0.12

now we have created the virtual multilink interface, yet the interface is not up/up, so its time to add interfaces into this multilink.

#interface Serial1/0-3
 #no ip address
 #encapsulation ppp
 #ppp multilink
 #ppp multilink group 1

on Client side we will configure the multilink same as in R1 but we will rely on DHCP to get ip address from R1 and that is done by using #ip address negotiable 
#interface Multilink1
 #ip address negotiated
 #ppp multilink
 #ppp multilink group 1

eventually the Multilink interface will become UP/UP state
time for some verifications:

R2-CLIENT#show ppp all
Interface/ID OPEN+ Nego* Fail-     Stage    Peer Address    Peer Name
------------ --------------------- -------- --------------- --------------------
Mu1          IPCP+ CDPCP+          LocalT   12.0.0.1                       
Se1/0        LCP+                  LocalT   12.0.0.1                       
Se1/1        LCP+                  LocalT   12.0.0.1                       
Se1/2        LCP+                  LocalT   12.0.0.1                       
Se1/3        LCP+                  LocalT   12.0.0.1                       
R2-CLIENT#

R2-CLIENT#show inter multilink 1
Multilink1 is up, line protocol is up
  Hardware is multilink group interface
  Internet address is 12.0.0.12/32
  MTU 1500 bytes, BW 6176 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open

As you can see above, the multilink bandwidth is the total of all links added to the MLPP and now it is 6176Kbps.

while the physical interface will have original BW
R2-CLIENT#show inter s1/0
Serial1/0 is up, line protocol is up
  Hardware is M4T
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open

 

 

 

Hope this was useful!

Samer R. Saleem