L3VPN - same subnet between sites

Answered Question

Hi there,


I have this customer who is reluctant to re-subnetting/reassign their site A,B,C,D, and E. All the CE router have ISDN backup to our PE-ISDN. We are using VPDN concept. The topology for this customer is fully mesh.


Sites A, B and C consist of subnet 192.168.1.x and there are lots of hosts. Each sites in A, B and C have a unique hosts. There are couple option/solution that spinning around my mind.


1. Since the PE-CE links address space comes from our service provider block, I've been thinking to NAT. Is it OK with this option? How about integration with ISDN? Would be any issue?


2. Offer L2 at site A, B and C. Since most of my PE are 3640/7200 not sure whether they support EToM or VPLS if I'm not mistaken, starting from 7600 series could offer the services. Can we have a mixture of L2/L3 on single VRF?


3. It is possible to do tunneling? GRE? IPSec? DMVPN?


Thanks in advance.


maher



Correct Answer by gramucisco about 9 years 3 months ago

The tunnel option is using L3 tunnels, so routing would be a challenge in this scenario if multiple sites have same subnet present.


If the sites are using the same class C network, you may have option to subnet it further and each site could be using unique subnet within that class C network.


Otherwise, VPLS or even VLL (if it is small number of sites) seems to be the next best option.


Combining NAT with MPLS VPN might become a nightmare from support point of view.


Correct Answer by ptaylor51 about 9 years 3 months ago

Maher hi


Your third option would be the a good way to go, this would allow end to end connectivety and you would not need to change any ip address.

Offering L2/L3 is another posibility but would require additional configuration technics.

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Correct Answer
ptaylor51 Wed, 11/28/2007 - 10:14
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Maher hi


Your third option would be the a good way to go, this would allow end to end connectivety and you would not need to change any ip address.

Offering L2/L3 is another posibility but would require additional configuration technics.

Correct Answer
gramucisco Wed, 11/28/2007 - 11:32
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The tunnel option is using L3 tunnels, so routing would be a challenge in this scenario if multiple sites have same subnet present.


If the sites are using the same class C network, you may have option to subnet it further and each site could be using unique subnet within that class C network.


Otherwise, VPLS or even VLL (if it is small number of sites) seems to be the next best option.


Combining NAT with MPLS VPN might become a nightmare from support point of view.


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