tunnel multilink

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Mar 14th, 2007
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Hi


I have two links between routers in two locations.


I can not route internet traffic through this links, dirctly.So im about to create tunnels on both links and using multilink I will create them in to a single link,


1. Is this possible to multilink with tunnel interfaces?

2. How would be the loadsharing?

3. Which of the links would be utilised highly or both will have even traffic.?


4.If im using ibgp for routing can i do loadbalancing without any probs?


pls guide.


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spremkumar Thu, 03/15/2007 - 01:19
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Hi


You wont be able to bundle tunnel interface and build a single multilink interface as you do with normal serial interfaces.


Do have multilinks created and create routes accordingly to have normal load sharing.


If you want to avoid over utilizing a single particular link then you can try configuring backup interface and backup load commands under the primary interface which will start shedding the load on the link mentioned as backup to it once the configured amount of bandwidth is exceeded on the main link..


regds


ilya.varlashkin Thu, 03/15/2007 - 14:41
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Use single tunnel interface with loopback interface as tunnel end-points, ensure load balancing for tunnel end-points, run routing over tunnel interface. Load balancing will be achieved by underlying tunnel encapsulation.

mohmmad.imran Sun, 03/18/2007 - 17:32
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Hi Rajiv,


1)It is not possible to use PPP multilink with Tunnel interfacs casue they do not have the mechanism to encap the packet with PPP.


2)As far as the Load Balancing is concerned you can achieve the same without using the Multilink


I am assuming that you have CEF enabled on the router.


interface Tunnel1

ip address x.x.x.x x.x.x.x

tunnel source LoopbackX

tunnel destination 1.1.1.1


ip route 1.1.1.1 255.255.255.255 serial0/0 192.168.10.1

ip route 1.1.1.1 255.255.255.255 serial0/1 192.168.20.1


once you define 2 static route with equal cost (AD and Metric) for tunnel destination the underlying forwarding mechanism(CEF) will build the forwading entry in FIB table and starts load-balance the traffic for tunnel destination betweeen the two physical Links.


3)Normally Cisco router does the load balancing between equal cost path on per destination basis. so it depends on the nubmer of the follow how your physical links are going to utilized, but if you want to distribute the traffic equally between both the physical links set the load balancing method on per-packet basis


to enbale the per-packet load balancing on physical us the following command:-

for eg:-

int se0/0

ip load-sharing per-packet

int se0/1

ip load-sharing per-packet


4)By defualt IBGP will install only the best path in the routing table even if he has the multiple path to the destination, in case if you want to load balanace the traffic using IBGP you can IBGP Multipath Features like this:-


router bgp 100

maximum-paths ibgp 3


Mohmmad Imran


paolo bevilacqua Sun, 03/18/2007 - 18:03
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Well, certainly it is not possible to bundle together tunnel interfaces, but it is possible to opposite, that is to run tunnel over a bundle of multilink interfaces.


This technique should resolve the original question.


The problem with per-packet load sharing is that there is always the possibility you will generate out-of-sequence packets, that is never an issue with multilink.

rajivrajan1 Mon, 03/19/2007 - 00:18
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hi ,


thanx a lot for replying everyones suggetion was very helpful.Let me try it in production network and i will comback to you.


Rated all u guys;)


thanx onceagain.


Rajeev.S

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