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Cisco 2811 and MLPPP

Unanswered Question

I have a Cisco 2811 that is connected to our Service Provider over an MPLS network running OSPF. We currently have (2) T1 cirucits and we are load balancing the two. I am going to add a third T1 but was told I need to do MLPPP.


First, will this router support it (it is the basic 2811 router nothing upgraded)and Second what is the config to accomplish this? And what do I need if anything to ask or tell my Service Provider to ensure they are doing their end properly?

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Richard Burts Wed, 01/24/2007 - 14:09
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Daniel


While I have not done it on a 2811 I do have multilink PPP on 3 T1s running quite successfully on a 2621. I am confident that your router will support it just fine. As far as I know support for multilink PPP is in all the images for that platform.


To configure MPPP you will configure the multilink interface which is the virtual interface and gets the IP address. You configure the physical serial interfaces and link them to the multilink interface. A config might look something like this:

interface Multilink1

ip address 10.126.209.86 255.255.255.252

no keepalive

no cdp enable

ppp multilink

ppp multilink fragment disable

ppp multilink group 1

interface Serial0/0

no ip address

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 1

interface Serial0/1

no ip address

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 1

interface Serial1/0

no ip address

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 1


You certainly do need to discuss this with your provider. They will need to make similar changes on their end. And you will need to coordinate so that you both are making changes at the same time.


HTH


Rick

Rick, thanks. This is pretty much what I figured. If you have done it on a 2621 it should also work on a 2811. I was worried about overhead as I heard this adds a lot.


But why do you have fragmentation disabled? Is it not needed?


It seems like we have or will have similar configs did you get the bandwidth expected after linking the T1s?

Richard Burts Thu, 01/25/2007 - 08:58
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Daniel


It is there because the provider wanted it included when we configured the multilink. I thought about taking it out of my posting but decided to post the entire working solution. I have seen other multilink configs that do not disable fragmentation.


HTH


Rick

allenelson Fri, 04/27/2007 - 09:11
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Can MLPPP be configured over an HDLC layer 2 circuit?


I've got 2 T1's that need to be bonded on a 2811 and 3 T1's that need to be bonded on a 3825. I'm not sure who provides one of the T's on the 2811 but do know the encapsulation is HDLC not PPP. Is this going to affect it in anyway?


I know it will be simple to change but I'm trying to minimize downtime and will plan around it if needed.


Also, with 2 different providers, is that going to affect the IP addressing for the interface?


If i set the interface with an IP address from 1 provider, will that affect the other DS1 from the 2nd?


multi 1 x.x.x.x x.x.x.x

ser0/0/0 no ip address (provider 1)

ser0/1/0 no ip address (provider 2)

Richard Burts Fri, 04/27/2007 - 09:55
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allen


First and most important: I do not believe that there is any way to do MLPPP over HDLC. While PPP and HDLC are similar protocols there are differences and MLPPP is designed to use PPP.


It is not clear to me how much impact there would be if the T1s are from different providers. I have not ever done it and can not speak from experience about it. It seems to me that as long as the T1s originate on the same router and they terminate on the same router that MLPPP should work (since the providers do not know or care what is transported over the T1s why would it matter). There has been some suggestion in the forum that with different providers that there might be different latencies on the T1s and that might cause performance problems.


And I do not see that having different providers would impact the addressing. With multiple T1s you need an address for each T1. With MLPPP you assign the IP address to the virtual interface not to the T1s and you only need 1 IP address for the router when using MLPPP. And why would the provider care what IP address is on the interface, so long as the link originated on your router and terminated on your other router, then the provider does not see nor do they care about the IP addresses on the link.


HTH


Rick

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