2xT1 combined in one link

Answered Question
Oct 29th, 2008

Hello guys,

I have two T1/s pointing to the HQ of the company and one redundant VPN failover with OSPF over Internet. Normally when both T1/s go down the OSPF recalculates the routing table and installs all routes learned over the VPN failover. I need to configure the network in a way when one of the T1/s goes down the entire connectivity to be placed over the failover VPN. Now if one of the lines goes down the traffic is still passed over the second T1 and the bandwidth is not enough. How can I get this working? Is the PPP Multilink a good solution in this case? I mean to combine the 2 T1/s in a Multilink.

Any help will be highly appreciated. Thank in advance!

rvr

Correct Answer by Amit Singh about 8 years 3 months ago

I addition to Rick's post, while configuring PPP multilink, use the command " multilink min-links links mandatory " and specify the minimum link as 2. In that case even if 1 T1 gows down the entire Multilink bundle with get disabled and it will fall back on VPN link.

HTH,

-amit singh

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Richard Burts Wed, 10/29/2008 - 05:39

rvr

PPP Multilink is certainly the best way to combine 2 T1s into a single logical entity. But I am not sure that it will solve your problem. If you put both T1s into a multilink and one T1 goes down then the multilink would still have one active member and would continue to function.

I would guess that if you want to change the routing logic if a single T1 of the pair goes down then you will need something like Object Tracking or IP SLA to track each T1 and remove the routes if a single T1 goes down.

HTH

Rick

Correct Answer
Amit Singh Wed, 10/29/2008 - 05:58

I addition to Rick's post, while configuring PPP multilink, use the command " multilink min-links links mandatory " and specify the minimum link as 2. In that case even if 1 T1 gows down the entire Multilink bundle with get disabled and it will fall back on VPN link.

HTH,

-amit singh

rvr_76bg@yahoo.es Wed, 10/29/2008 - 06:04

Excellent reply! Would you please refer me to a cisco doc for how to configure ppp multilink.

rvr

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