Question : Multilink ppp Speed Problem

I have a problem when i do multilink ppp to bond 2 dsl lines.

One of the lines is a 2meg SDSL and the other line is a 0.5 meg IP stream ADSL.

the 2meg on its own , runs at 2meg speed when i do a line test, when i run a line test on the 0.5 meg ADSl, i get 0.5meg speed.

When when i run a line test when the 2 lines are part of MLP bundle, i get 1 meg speed.

It doesnt seen to make any sense, when i check the lines on the LNS, i can see they have formed an MPL bundle...so why do i get 1meg speed when the lines are combined as a bundle?

MY config on the cisco router is below.....



!
controller DSL 0/1/0
 mode atm
 line-term cpe
 line-mode 2-wire line-zero
 dsl-mode shdsl symmetric annex B
 line-rate auto
!
!
!
interface FastEthernet0/0
 ip address 192.168.16.1 255.255.255.240
 ip nat inside
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface ATM0/0/0
 no ip address
 no atm ilmi-keepalive
 dsl operating-mode auto
 pvc 0/38
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface ATM0/1/0
 no ip address
 no atm ilmi-keepalive
 pvc 0/38
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface Dialer0
 ip address negotiated
 ip nat outside
 encapsulation ppp
 dialer pool 1
 dialer persistent
 dialer-group 1
 ppp authentication chap callin
 ppp chap hostname xxxxxxxxxxxxxxxx
 ppp chap password 0 test
 ppp multilink
!
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer0
!
!
no ip http server
no ip http secure-server
ip nat inside source list 101 interface Dialer0 overload
!
access-list 101 permit ip 192.168.16.0 0.0.0.15 any
dialer-list 1 protocol ip permit
!
!
!
control-plane
!
!
!

Answer : Multilink ppp Speed Problem

router eigrp XXX
 network x.x.x.x t.t.t.t
 network x.x.x.x t.t.t.t (repeat as needed)
 variance 10
 maximum-paths 6
!

The "variance 10" means once it's found the BEST link(s) (i.e. equal-cost load-sharing), continue considering additional links whose metrics are up to 10x the value of the best link(s) until you've hit the maximum-paths (I think it defaults to 6).  Links are used inversely proportional to their metric, and metric is mostly based on bandwidth in EIGRP.

Two caveats: once the links are selected, their proportions have to be "adjusted" to fit CEF's load-sharing mechanisms.  Per prefix, there are 16 buckets that can be assigned to paths.  In your case, you're hoping for 4/5 over the 2Mb link and 1/5 over the 512k link, but you'll (probably) end up with 13/16 over the 2Mb link and 3/16 over the 512k link, which isn't exactly the split you'd want.  Also, by default FLOWS are divided up over the possible paths based on the CEF proportions, not PACKETS.  If your flows are consistently different enough, you could end up with big-packet flows over one link and small-packet flows over the other link; the flows are distributed as the numbers say, but the bandwidth isn't.  The only way around this, and I do NOT recommend it, is "ip load-sharing per-packet" on both links to do per-packet load-sharing.