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New Member

Effectively getting 3mb transfer speeds on two Tl's - CEF,IMUX,MPPP....???

Fellow Engineers,

I've got a conceptual question that I've been wrestling with due to a customer inquiry....I recently had a customer inquiry that stated that he was getting roughly only 1.5 mb transfer speeds over his 2 T-1's to the internet. Excluding other factors such as servers, firewalls internet congestion, etc....should this customer be capable of getting near 3mb download speeds on a individual user session over his 2 Tl's??? Currently, the customer is configured with 2 T1's to the same internet gateway with equal cost static routes on both ends utilizing fast switching with destination load sharing. I'm under the assumption the current set up will only allow for near T1 speeds for a each user session because each transmission will utilize only one T1 with the destination based load sharing causing a user transmission to pick only one path or T1 for the entire session and each T1 is only clocked at 1536mb.

I'm basically wrestling with idea of when a user in this scenario should be capable of getting 3md transfer speeds....

If I use a bundling technique such as MPPP or CEF with per packet load sharing, will that allow a user on this network theoretically to reach near 3mb transfer speeds for a individual user session. Moreover, could someone further explain the differences in terms of latency and transfer speeds from a individual user standpoint with the following network scenarios:

1 - 2 T1's with CEF per packet (equal cost statics)

2 - 2 Tl's with fast switching (equal cost statics/destination load sharing)

3 - 2 T1's imuxed (utlizing added hardware on each end)

thanks for your input,



Re: Effectively getting 3mb transfer speeds on two Tl's - CEF,IM


1. Equal Cost statics will get you little depending on the switching mechanism you use. As you mentioned you might see certain sessions consume all BW but stay on one link. Per packet with CEF gets you to use both or process switching can achieve this as well at a cost of CPU cycles.

2. Fast switching gets you what you have now, per dest.

3. MLPPP (Multilink PPP) is an L2 bundling of the two T1's. The load sharing is done by PPP. It has one logical bundle interface to manipulate at either end and is very nice and easy to manipulate once up and running. If I were to recommend something to go with if you are looking to increase a customer's BW I would go with this. Depending on platform types though MLPPP can be pretty CPU/resource intensive.

Hope this helps,


New Member

Re: Effectively getting 3mb transfer speeds on two Tl's - CEF,IM


Assuming I went with your recommendation, I would need to configure MLPPP on both ends of the link to allow the bundling of traffic in both directions correct?? I might run into issues with our internet backbone group allowing for MLPPP to be configured on a gateway router considering the cpu/resource issue as you have mentioned. Secondly, are their hardware issues that need to be addressed, the customer has a 2620 with 2 WICS and on the other end there is most likely a GSR with a chanelized DS3 interface or a 7507 with a 8 port FSIP card at the internet gateway. From what I know about our internet group they recommend using CEF with per packet using equal cost statics or EBGP multihop if running BGP. I guess I will need to look into it.....I know the customer will want to avoid the additional investiment in hardware with having to buy a IMUX. CEF or MLPPP seem to be good solutions. Well, just to clarify, will both per packet with CEF and MLPPP both theoretically allow a individual user get 3megs of transfer speeds under ideal circumstances????

thanks for your assistance,


New Member

Re: Effectively getting 3mb transfer speeds on two Tl's - CEF,IM

Hi guys,

I am now taking CCNA, working as a Helpdesk Analyst in Singapore, my boss give me an chance to set an network using 2 2500 router, a cisco switch, 2 128k leased line, similar to scenario stated.

How can I setup? Is there any examples I can work with? Actually, I had post an topic asking for help, but no 1 helped me, subject is 'Ask the Expert - Please Help me URGENT!'.

I need some examples for setting up the both router and switch. I hope to take this time as a chance to learn and hope you guys out there will guide me through, email me at

Thanks a lot guys, looking forward for yr reply.


Jeffery Miow

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