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MPLS IP Scheme

Hi Guys,

Can someone please tell me why the WAN addressing for these 2 sites is invalid.  
 
Site1
Customer IP Address Range(s) 192.168.4.0/24
LAN Interface Address  192.168.4.111
WAN Interface Address  192.168.4.222
 
Site2
Customer IP Address Range(s) 192.168.2.0/24
LAN Interface Address           192.168.2.111
WAN Interface Address    192.168.2.222

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tickleonthetum
Asked:
tickleonthetum
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2 Solutions
 
grbladesCommented:
Hello tickleonthetum,

The WAN and LAN IPs are logically on the same network.

Regards,
grblades
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tickleonthetumAuthor Commented:
Hi thanks for this so far.  Can you recommend how I address the problem please what would be your recommendation to change the WAN IP addresses to.

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grbladesCommented:
The LAN addresses are correct as they are. You just want a small IP address range for the MPLS network. I would go for something like 192.168.250.1 and 192.168.250.2 which is something a long way off what you are using for your private networks so even if you add lots more sites it wont be an issue.
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lrmooreCommented:
Agree with grblades. We typically use a /30 network address for WAN links, and sites 1 and 2 are different because they do not connect directly with each other, but rather with the MPLS cloud. example:
CER=Customer Edge Router (your router WAN interface)
PER=Provider Edge Router (your telco's router interface)
Site1:
 CER = 192.168.255.2 255.255.255.252
 PER = 192.168.255.1 255.255.255.252

Site2:
 CER= 192.168.255.6 255.255.255.252
 PER= 192.168.255.5 255.255.255.252
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grbladesCommented:
lrmoore, quick question for you.
With MPLS is it effectivly just like a private network?
I was thinking of using the full class C as it would make it easier if more sites were added in the future as it would avoid having to reconfigure the subnet mask as the range of usable IP addresses was used up.
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lrmooreCommented:
It doesn't matter. It is purely an independent single link between your router and the provider's router at every location. It will never require more than a /30 subnet. If you have 100 sites, it won't matter at all if some are 192.168.254.x/30 and some are 172.30.99.x/30 and some are 10.174.255.x/30
The MPLS providers almost universally request you to use /30

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tickleonthetumAuthor Commented:
Guys your help has been absolutley great so far.  One more quick query connected to this.  I'm a Windows and Exchange engineer not "high level" networks.  The person who originally put this together has spec'd up the following :

Site1 subnet of 192.168.0.x - 192.168.7.x  subnet mask 255.255.248.0

Site2 subnet mask of 192.168.8.x subnet mask of 255.255.255.0

My issue is the subnet size for site1 is absolutley huge surley the broadcast traffic would be massive ?

I'm assuming that if this wasnt changed for the better the 2 subnets would communicate through the MPLS cloud without any problems ?



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tvman_odCommented:
MPLS is not like a LAN with a single broadcast domain. The cloud could be very complex and normally carrier controls addressing schemas for edge routers where you access the network. Naturally you cannot have two interfaces from the same subnet on different interfaces of the router.
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grbladesCommented:
Broadcast traffic does not go across routers anyway so it is not an issue in MPLS terms.

As far as local network is concened it depends on how many machines you have and the speed of the network. About 7 years ago 250 machines per network was the recommended maximum but network speeds can be much faster now and that goes for the speeds of the computers aswell.
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tvman_odCommented:
1. Broadcasting depends on number of hosts, not the actual addressing space
2. You don't have to use it as a single LAN segment. You can divide it on segments of appropriate size.
3. As I see it's just for routing purposes only, it means that a big block of IP adresses located behind your border router on Site1
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tickleonthetumAuthor Commented:
So grblades, I'll give you the points in 2 seconds, lets just make sure I get this right ....

I can have the following :

Site 1:

Customer IP Address Range(s) 192.168.0.x - 192.168.7.x  s/n 255.255.248.0
LAN Interface Address  192.168.0.1
WAN Interface Address  : 192.168.250.1 s/n 255.255.255.252


Site 2:

Customer IP Address Range 192.168.8.x s/n 255.255.255.0
WAN Interface Address : 192.168.250.2 s/n 255.255.255.252

Does that sound solid ?
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grbladesCommented:
Yes that looks fine.
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tvman_odCommented:
Is it point to point connection or MPLS?
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lrmooreCommented:
No. Site 1 and Site 2 do NOT SHARE the same subnet on the WAN link on MPLS network.
Follow my example above.

Site 1:
WAN Interface Address  : 192.168.250.1 s/n 255.255.255.252
Site 2:
WAN Interface Address : 192.168.250.2 s/n 255.255.255.252

>Site1 subnet of 192.168.0.x - 192.168.7.x  subnet mask 255.255.248.0
Just a word of caution: This is a case of supernetting, or summarization of Class C address space and not a true valid subnet mask. Most current TCP/IP stacks will work, but some older devices and systems may not recognize anything other than a /24 class C mask with class C addresses.
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tickleonthetumAuthor Commented:
lrmoore okay I'm sorry I'm getting confused can you take, my ip scheme for site 1 and site 2 and let me know what CER AND PER based on my setup you would use.  Sorry if I sound thick I'll admit I'm having to learn here.  
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tickleonthetumAuthor Commented:
Sorry got it thanks guys !!
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