Multilink PPP Question

L0man · Guest

I have a strange situation. I am connecting a 7206VXR to a 7507 via
MPPP over 2 T1 leased lilnes. In my test lab, I used another 7206 to
simulate the 7507 (prouduction box) with both back-to-back cables and
across the T1s themselves and had no problems. But, when I connect
the 7206 to the 7507 I get horrible response times across the link.
Just pinging produces response times of 20ms to 500ms. I worked with
the TAC for a couple of hours last night, but wasn't able to resolve
during my scheduled downtime, so I had to call the thing off.
Here is the pertinent portion of my 7507 config:

no ip cef
ipx routing 000b.45ce.7000
!
controller T1 1/0/0
channel-group 0 timeslots 24
!
controller T1 1/0/1
channel-group 0 timeslots 24
!
controller T1 1/0/2
!
controller T1 1/0/3
!
controller T1 1/0/4
!
controller T1 1/0/5
!
controller T1 1/0/6
!
controller T1 1/0/7
!
controller T1 1/1/0
!
controller T1 1/1/1
!
controller T1 1/1/2
!
controller T1 1/1/3
!
controller T1 1/1/4
!
controller T1 1/1/5
!
controller T1 1/1/6
!
controller T1 1/1/7
!
!
!
!
!
interface Loopback0
ip address 10.192.254.6 255.255.255.255
!
interface Multilink1
ip address 10.192.10.41 255.255.255.252
no ip route-cache
ip ospf message-digest-key 1 md5 xxxxxxxxxx
no ip mroute-cache
ipx network 9B848A1B
no cdp enable
ppp multilink
no ppp multilink fragmentation
multilink-group 1
!
! SNIP
!
interface Serial1/0/0:0
no ip address
encapsulation ppp
no ip route-cache
no fair-queue
ppp multilink
multilink-group 1
!
interface Serial1/0/1:0
no ip address
encapsulation ppp
no ip route-cache
no fair-queue
ppp multilink
multilink-group 1
******************************

Here is the 7206 config:

controller T1 1/0
framing esf
linecode b8zs
channel-group 0 timeslots 24
no yellow generation
no yellow detection
!
controller T1 1/1
framing esf
linecode b8zs
channel-group 0 timeslots 24
no yellow generation
no yellow detection
!
controller T1 1/2
framing esf
linecode b8zs
no yellow generation
no yellow detection
!
controller T1 1/3
framing esf
linecode b8zs
no yellow generation
no yellow detection
!
!
! SNIP
!
interface Loopback0
ip address 10.192.254.11 255.255.255.255
!
interface Multilink1
ip address 10.192.10.42 255.255.255.252
no ip route-cache
ip ospf message-digest-key 1 md5 xxxxxxxxxx
no ip mroute-cache
ipx network 9B848A1B
no cdp enable
no ppp multilink fragmentation
ppp multilink
multilink-group 1
!
! SNIP
!
interface Serial1/0:0
no ip address
encapsulation ppp
no ip route-cache
no fair-queue
ppp multilink
multilink-group 1
!
interface Serial1/1:0
no ip address
encapsulation ppp
no ip route-cache
no fair-queue
ppp multilink
multilink-group 1

Cisco had me add the "no ip route-cache" ,"no ip mroute-cache", and
"no ppp multilink fragmentation" commands while trying to fix the
problem.

Thanks in advance for any suggestions.

Brian Lehigh · Guest

Let me know what you come up with on this one. I am preparing to implement
this same thing between two 7206VXR's on Monday. My lab environment was a
little different (I'm using two 2514's but it does the trick), however, the
IOS that I'm running on them didn't support the "interface multilink"
command so I had to do it a little different. Here's what I had to do (only
config related to MLPPP shown):

-----------------------------------------
multilink virtual-template 1
!
interface Loopback1
ip address 64.118.98.234 255.255.255.252
no ip directed-broadcast
ip ospf message-digest-key 20 md5 xxxx
!
interface Serial4/0:0
no ip address
encapsulation ppp
load-interval 30
ppp multilink
!
interface Serial4/1:0
no ip address
encapsulation ppp
load-interval 30
ppp multilink
!
interface Virtual-Template1
ip unnumbered Loopback1
no ip directed-broadcast
ppp multilink
!
-----------------------------------------
I, as you, did not notice any delay in ping response times. Actually, the
ping responses improved slightly. I do believe, however, that I will deploy
it in the fashion that you have used. It looks much cleaner.

-Brian

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