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MPLS and Ip addressing schemes

Answered Question
Nov 1st, 2005
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Hi,


I currently work on a system that connects several sites together using fixed leased lines. These leased lines for a ring topology for all our sites.


Each site has a wic-1t card ( per link ) and the local and opposite end of the link has a WAN ip address that is in the same subnet for that particular WAN link.


My questions is this ( hope its not too stupid !):


We are looking to migrate to an MPLS core network and hence each site will be as "close" to every other site and so on. My question is regarding the new WAN Ip- addresses and whether they will have to be in a different subnet for each site or will they all have to be in the same subnet ?


i.e would i potentially have WAn address es of 10.1.1.1 for site a

10.1.1.2 for site b

10.1.1.3 for site c


and so on in the same subnet.


Or, will it be:


site a wan address 10.1.1.1/30

site b wan address 10.1.1.5/30

site c wan address 10.1.1.8/30


and so on ?


I cant get my head round this and any advice is much appreciated...


regards


Richard

Correct Answer by mounir.mohamed about 11 years 9 months ago

Dear,


The MPLS doesn’t change any meaning of ip address schema else that in MPLS/VPN you can use overlap address with different VPNs,

Anyway regarding your question the branches WAN IP’s have to be in a different subnet for each site as soon as they in the same VRF, the only deferent that your routers (CE) will peer with the ISP routers (PE) by /30 instead of peering every branch with the central or the hub router then the connectivity between each branch will be done through the ISP core network


Best Regards,

Mounir Mohamed


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spremkumar Tue, 11/01/2005 - 23:16
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Hi


I feel you are migrating from the normal plain vanilla ip services to MPLS backbone being provided by your SP ,if thats the case i feel theres no need for changing any ip address space between your locations.

you can keep the /30 intact between all these locations.

i would also suggest to take ur SP in confidence about the addressing scheme part.


Also revert whether you are planning to enable MPLS in ur fully meshed connectivity if yes do revert what kinda topology you have at present and the boxes which are in use at present in locations for establishing the connectivity between the locations .


regds


rsd1234 Wed, 11/02/2005 - 12:22
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Hi,


thanks for you reply. I will clarify a few points.


1. We have to change the WAN IP adreeses as even though this is a private network when it was set up the original instllation team used public addresses. We are therefore taking this opportunity to "tidy up" these addresses.


2. The current network has 2 leased lines leaving every site to form a ring topology. As I stated each link is set up with an ip address in the same subnet at either side of the link. These are therefore all point - 2 -point communication links.

When we migrate to MPLS there will be no point-2-point links and instead we will have point-2-mulipont links.

Therefore should I be looking at seting all the WAN IP addresses to be in the same subnet or not.

Each LAN has its own individual subnet which are all ok, it is just the WAN IP addresses. I need to know how these should be ip'ed (i.e. same subnet or not same subnet ) so I can start to plan a rollout strategy.


regards


Richard

Correct Answer
mounir.mohamed Wed, 11/02/2005 - 12:29
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Dear,


The MPLS doesn’t change any meaning of ip address schema else that in MPLS/VPN you can use overlap address with different VPNs,

Anyway regarding your question the branches WAN IP’s have to be in a different subnet for each site as soon as they in the same VRF, the only deferent that your routers (CE) will peer with the ISP routers (PE) by /30 instead of peering every branch with the central or the hub router then the connectivity between each branch will be done through the ISP core network


Best Regards,

Mounir Mohamed


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