Query for Primary-Backup

Unanswered Question
Dec 30th, 2008

Dear expert need your help for primary-backup solution

attached a rough diagram for reference

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Site-1 and Site-2 will be primary and connected to different router of provider

Site-3 will be backup of Site-1 and Site-2

Example:

Customer want 150MB bw as Primary (site-1 + Site-2) and 150Mb as Backup (Site-3)

1-How can I control total of 150MB BW for site-1 and site-2 as these are coming on different router

(If I put rate-limit of 150MB on both primary site then how can I control total utilisation of 150 as total of both site will be 300MB)

2-How can I make Site-3 as Backup of site-1 and site-2 (Say )

Please let me know for any clarification required

I have this problem too.
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Giuseppe Larosa Fri, 01/02/2009 - 12:19

Hello Mahesh,

1)

As you wrote there are some limits to the traffic control you can achieve

see section point-to-point and point-to-cloud

http://www.cisco.com/en/US/tech/tk828/technologies_q_and_a_item09186a00800a43f5.shtml#wp27879

with what site have primary site (site1 and site2) to communicate ?

Can we thin of primary site as a site with two CE routers that connect to the same customer site or are they distinct sites ?

2)

this can be made with different routing features like BGP conditional advertising for example.

or simply the backup site advertise the same routes as site1 and site2 but until one of them is up site3 is not used.

this can be achieved with some BGP tuning for example on local preference so that all other sites will use the sites.

You can build a hierarchy of routing both directions

site1 preferred both ends limited to 150 Mbps

site 2 second preferred

site3 used only if site1 and site2 are out of service /isolated (disaster recovery)

if you do so you gain control on traffic because only one site is used at a given time.

Again if site1,site2 are two CE nodes of the same site you can implement a hierarchy.

The customer can say that we would want to see both site1 and site2 used at the same time.

Some choices and tradeoffs need to be done.

Hope to help

Giuseppe

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