Multilink PPP Interface

Unanswered Question

Hello guys,

I have 2xT1 bundled in a Multilink PPP Interface, when one of the T1/s goes down the Multilink interface goes down for awhile too and I lose connectivity to the other side for like 5-7 seconds which makes all IP Phones to reset. Then the Multilink comes back up. The reset of the IP Phones is unacceptable please help with this. Both T1/s a connected to 28xx routers on both sides.

Regards,

rvr


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mohindersingh Mon, 01/19/2009 - 07:23
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HI Rvr,


There is a option in multilink to set the minimum links required to keep the multilink bundle up. You can set the minimum value to 1 so that if one link goes down, it will not affect the multilink bundle connectivity.


ppp multilink min-link 1


Please rate the post, if finds useful.


Mahi

Let me explain the entire picture. Both T1/s don't have IP addresses. The multilink interface has IP add and participates in the OSPF process. When one of the lines goes down OSPF loses its OSPF peer on the other side for several seconds and we cannot pass traffic over the lines even one of the two lines is up. Then OSPF adjacency comes back up and everything is back to normal. See the output from the log:


Jan 19 15:50:08.739 IST: %OSPF-5-ADJCHG: Process 30, Nbr 192.168.x.x on Multilink1 from

FULL to DOWN, Neighbor Down: Dead timer expired

Jan 19 15:50:34.368 IST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/2/0, chan

ged state to down

Jan 19 15:50:39.436 IST: %OSPF-5-ADJCHG: Process 30, Nbr 192.168.x.x on Multilink1 from

LOADING to FULL, Loading Done

Jan 19 16:02:19.146 IST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/2/0, chan

ged state to up

Jan 19 16:03:20.584 IST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/2/0, chan

ged state to down

Jan 19 16:03:22.888 IST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/2/0, chan

ged state to up


Rick Morris Mon, 01/19/2009 - 07:24
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I would recommend removing the MLPPP config and running equal weight static routes on the lines. I like this set-up much better. Perhaps nothing techinical about it but I feel it gives me more control of my traffic and lines.


In this case you would use:

ip route 0.0.0.0 0.0.0.0 Serial 0/0/0

ip route 0.0.0.0 0.0.0.0 Serial 0/1/0


then if you needed to shape your traffic

ip 63.163.10.100 255.255.255.255 Serial 0/0/0


etc...


Then you would build your traffic to a loopback interface so that no matter what happens to one line the other will still have traffic.


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