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Bonding two T1's on a DS3 between a 7204 and 7507

Unanswered Question
Apr 2nd, 2003
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I have a DS3 that we use to carry multiple WAN T1's between sites. We breakdown each T1 and then sub-interface them. One site is a 7204 and the other is a 7507.

We use one of the T1's for traffic between these two sites. We are now pushing that pipe to it's limit and would like to take an adjacent (unused) T1 and bond the two together to get twice the bandwidth. How do I do this?

Do I use ppp multilink on both and build a multilink group?

Which IOS interface commands do I use?

One other thought - is there a way to build a single interface from two T1 time slots to provide twice the bandwidth?



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rbristow Thu, 04/03/2003 - 11:13
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You can use a MULTILINK interface to bond multiple T1 circuits, but be aware that 100% of the outbound packets will be Process switched. MPPP and the switching path add substantial load to the CPU. If you're just doing 2xT1 for one remote site you should be OK. But this is not a scalable solution.

CEF switching will do Per-Destination load sharing by default, or you can also use Per-Packet load sharing with a command on the interfaces.


Rob Bristow

CCIE #3335

abatson Fri, 04/04/2003 - 07:29
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Is there a big[er] CPU hit with per-packet CEF balancing? My ISP's telling me to do the CEF balancing with a new 2 X T1 solution I'm buying. With all the millions of destinations on the Internet, we're afraid that a single host (CNN.COM, or other hi-volume site) will soak up too much bandwidth on a single ckt. Doing per-packet balancing will aleviate this, but how much more CPU does it take to do a round-robin, versus assigning specific destinations to specific ckts? (where CEF shines...)


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