Number of Core routers

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Jun 15th, 2009
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Hi,


Our client is planning to upgrade their existing two core routers of their MPLS backbone. They are considering three core and four core design.


We would like to know if there are any drawbacks of having three core design against a two core or four core design?


Regards,

Prakash

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Giuseppe Larosa Mon, 06/15/2009 - 02:22
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Hello Prakash,

if the core routers have a full mesh you need to go through only two of them for each pair of source/destination IP addresses or other services


Hope to help

Giuseppe


shivlu jain Mon, 06/15/2009 - 04:37
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Hi Prakash


It looks like that your client is runnig SP network. 3 core design means 3 cut not out or your are talking about hierachical. Please make it more clear so that we could the problem.


regards

shivlu jain

prakashj Mon, 06/15/2009 - 04:56
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Yes..its an MPLS network...at present there are 14 PE routers connected to two core routers..


Now the client would like to add another 4 PE routers..as there are no free slots available in the cusrrent core routers, he wants to look into the possibility of distributing the links between three core routers...


But if there are any design concerns with 3 core design, then he is ready to upgrade the existing core to a higher model with more slots.


Regards,

Prakash

shivlu jain Mon, 06/15/2009 - 05:11
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Hi Prakash


In face I have never seen the 3 core design but instead of 3 4 is better. It would be like that 4 will be your core and rest will move around it.

But I can purpose a one method where in you can install a switch and terminate all the links on switch and one port will be connected with router and create sub interfaces.


regards

shivlu jain

prakashj Mon, 06/15/2009 - 05:21
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Thanks Shivlu for your reply...


I also suggested to have a 4 core or a 2 core which has more slots. At present they have two GSRs and all the PE routers are connected using STM-16, STM-64 and 10GE uplinks. Now they would like to add more PE routers with 10GE uplinks and we suggested to move to CRS-1 as it can accomodate more interfaces per slot.


But they would like to look at the possibility of adding another GSR in the core and distribute the PE links.


Hence if I have to suggest him a

2 X CRS-1 core, I have to give them justifications against 3 core design.


Regards,

Prakash

shivlu jain Mon, 06/15/2009 - 05:38
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Hi Prakash


Currently Every PE is connected by one P and another P. Hopefully both P routers are connected back to back. But when the third P will be added in that case you need to add a switch and create a local peering, so that when the traffi will come to P and there after need to move to another P, In that case it will forward by switch. The main disadvantage of this is that you are increasing the broadcast domin of OSPF. The another option is that connect the P routers like given


P-----P--------PE

\ospf/

\ /

\/

P---------PE


regards

shivlu jain

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