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Help in understanding an MPLS network (MPLS newbie)

 
 
ttripp
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      11-12-2007
I've inherited an MPLS network, and I've not worked with MPLS before.
The more I read, the more confused I am about the network I have.

I have a dozen sites, all connected to a Bellsouth (now AT&T) MPLS
network. Each site has a T1 circuit, and the circuit is configured as
frame-relay on each sites router. I understand this part OK.

Now to the part I don't understand. Each remote site is connected
back to the main site through VPN tunnels. So, each remote site has
one VPN tunnel back to the main site, and the main site has a dozen
tunnels, one to each remote site. Then, each site has a dozen static
routes, all pointing the their local router's WIC IP address.

Is this a typical MPLS setup? What I thought what MPLS did was not
unlike what a traditional frame-relay network did; the customer's
routers handed the WAN traffic to the provider's network, which
through various pieces of routing magic delivered the packets to the
customer's routers on the opposite end. No need to set up VPN
tunnels, and you use a IGP to handle the routing.

Each frame-relay interface is point-to-point, with the IP address part
of a /30 network, with one end being the local router, and the other
end being the AT&T router. Is this also typical?

Most MPLS documentation seems to be geared towards how the provider
sets up their network, not how the customer sets up his part. Any
help would be greatly appreciated, as I have absolutely no
documentation on how this setup came to be. Thanks.

 
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ttripp
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Posts: n/a
 
      11-12-2007
On Nov 12, 1:23 pm, ttripp <(E-Mail Removed)> wrote:
> I've inherited an MPLS network, and I've not worked with MPLS before.
> The more I read, the more confused I am about the network I have.
>
> I have a dozen sites, all connected to a Bellsouth (now AT&T) MPLS
> network. Each site has a T1 circuit, and the circuit is configured as
> frame-relay on each sites router. I understand this part OK.
>
> Now to the part I don't understand. Each remote site is connected
> back to the main site through VPN tunnels. So, each remote site has
> one VPN tunnel back to the main site, and the main site has a dozen
> tunnels, one to each remote site. Then, each site has a dozen static
> routes, all pointing the their local router's WIC IP address.
>
> Is this a typical MPLS setup? What I thought what MPLS did was not
> unlike what a traditional frame-relay network did; the customer's
> routers handed the WAN traffic to the provider's network, which
> through various pieces of routing magic delivered the packets to the
> customer's routers on the opposite end. No need to set up VPN
> tunnels, and you use a IGP to handle the routing.
>
> Each frame-relay interface is point-to-point, with the IP address part
> of a /30 network, with one end being the local router, and the other
> end being the AT&T router. Is this also typical?
>
> Most MPLS documentation seems to be geared towards how the provider
> sets up their network, not how the customer sets up his part. Any
> help would be greatly appreciated, as I have absolutely no
> documentation on how this setup came to be. Thanks.


Actually, I got a detail wrong. Three of the sites (including the
main site) are connected through frame-relay, but the other ten are
connected through regular T1. I should point out that AT&T is the
vendor for most, but not all, of these local connections. The MPLS
network is pure AT&T.

 
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stephen
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Posts: n/a
 
      11-12-2007
"ttripp" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> On Nov 12, 1:23 pm, ttripp <(E-Mail Removed)> wrote:
> > I've inherited an MPLS network, and I've not worked with MPLS before.
> > The more I read, the more confused I am about the network I have.
> >
> > I have a dozen sites, all connected to a Bellsouth (now AT&T) MPLS
> > network. Each site has a T1 circuit, and the circuit is configured as
> > frame-relay on each sites router. I understand this part OK.
> >
> > Now to the part I don't understand. Each remote site is connected
> > back to the main site through VPN tunnels. So, each remote site has
> > one VPN tunnel back to the main site, and the main site has a dozen
> > tunnels, one to each remote site. Then, each site has a dozen static
> > routes, all pointing the their local router's WIC IP address.


do you have documentation?

if not - thats the 1st thing to fix.
> >
> > Is this a typical MPLS setup? What I thought what MPLS did was not
> > unlike what a traditional frame-relay network did; the customer's
> > routers handed the WAN traffic to the provider's network, which
> > through various pieces of routing magic delivered the packets to the
> > customer's routers on the opposite end. No need to set up VPN
> > tunnels, and you use a IGP to handle the routing.


Yes - or at least that is the way the ones i have used work.
the serial link carries F/R format packets, but uses it as a point to point
link to peer to the PE router.
you only need multiple PVCs if you are either
1. crossing a "real" F/R network to get to the MPLS bit, or
2. for some logical structure reason across a point to point serial link (we
use it for multi VPN since different VPNs can use different PVCs on the same
WAN link to keep traffic separation).

but nothing stops you adding tunnels on top of that for some reason, since
it is just another IP network
- one i get involved in does it as:
internal net + OSPF -> GRE -> IPsec -> "cloud" with MPLS.

> >
> > Each frame-relay interface is point-to-point, with the IP address part
> > of a /30 network, with one end being the local router, and the other
> > end being the AT&T router. Is this also typical?
> >

Yes.

> > Most MPLS documentation seems to be geared towards how the provider
> > sets up their network, not how the customer sets up his part. Any
> > help would be greatly appreciated, as I have absolutely no
> > documentation on how this setup came to be. Thanks.


well, the carrier should have documentation if they want to be able to fix
it when it breaks- so get hold of your contact and get that bit.

you shouldnt need any "MPLS specific" docs for the customer part of an MPLS
network.
All the label switching happens in the core of the MPLS network, and is
intended to simulate a private dedicated IP cloud for each VPN.
So - treat it like a private any to any IP net and ignore the MPLS label on
the tin........
>
> Actually, I got a detail wrong. Three of the sites (including the
> main site) are connected through frame-relay, but the other ten are
> connected through regular T1. I should point out that AT&T is the
> vendor for most, but not all, of these local connections. The MPLS
> network is pure AT&T.


sounds like some of your sites have to go via a F/R access network to get to
the MPLS cloud.

a lot of carriers do this at lower density parts of the network since they
have big F/R & ATM networks, they still work, and they are busy taking
people off those direct services, so spare capacity is there.

However - you often lose facilities if you go to MPLS via a "real" Frame or
ATM cloud instead of just using it on the access point to point link - fewer
or no QoS levels, and maybe limits to how full you can run the circuit.
>

--
Regards

http://www.velocityreviews.com/forums/(E-Mail Removed) - replace xyz with ntl


 
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ttripp
Guest
Posts: n/a
 
      11-12-2007
On Nov 12, 2:31 pm, "stephen" <(E-Mail Removed)> wrote:
> "ttripp" <(E-Mail Removed)> wrote in message
>
> news:(E-Mail Removed) ups.com...
>
> > On Nov 12, 1:23 pm, ttripp <(E-Mail Removed)> wrote:
> > > I've inherited an MPLS network, and I've not worked with MPLS before.
> > > The more I read, the more confused I am about the network I have.

>
> > > I have a dozen sites, all connected to a Bellsouth (now AT&T) MPLS
> > > network. Each site has a T1 circuit, and the circuit is configured as
> > > frame-relay on each sites router. I understand this part OK.

>
> > > Now to the part I don't understand. Each remote site is connected
> > > back to the main site through VPN tunnels. So, each remote site has
> > > one VPN tunnel back to the main site, and the main site has a dozen
> > > tunnels, one to each remote site. Then, each site has a dozen static
> > > routes, all pointing the their local router's WIC IP address.

>
> do you have documentation?
>
> if not - thats the 1st thing to fix.
>
>
>
> > > Is this a typical MPLS setup? What I thought what MPLS did was not
> > > unlike what a traditional frame-relay network did; the customer's
> > > routers handed the WAN traffic to the provider's network, which
> > > through various pieces of routing magic delivered the packets to the
> > > customer's routers on the opposite end. No need to set up VPN
> > > tunnels, and you use a IGP to handle the routing.

>
> Yes - or at least that is the way the ones i have used work.
> the serial link carries F/R format packets, but uses it as a point to point
> link to peer to the PE router.
> you only need multiple PVCs if you are either
> 1. crossing a "real" F/R network to get to the MPLS bit, or
> 2. for some logical structure reason across a point to point serial link (we
> use it for multi VPN since different VPNs can use different PVCs on the same
> WAN link to keep traffic separation).
>
> but nothing stops you adding tunnels on top of that for some reason, since
> it is just another IP network
> - one i get involved in does it as:
> internal net + OSPF -> GRE -> IPsec -> "cloud" with MPLS.
>
>
>
> > > Each frame-relay interface is point-to-point, with the IP address part
> > > of a /30 network, with one end being the local router, and the other
> > > end being the AT&T router. Is this also typical?

>
> Yes.
>
> > > Most MPLS documentation seems to be geared towards how the provider
> > > sets up their network, not how the customer sets up his part. Any
> > > help would be greatly appreciated, as I have absolutely no
> > > documentation on how this setup came to be. Thanks.

>
> well, the carrier should have documentation if they want to be able to fix
> it when it breaks- so get hold of your contact and get that bit.
>
> you shouldnt need any "MPLS specific" docs for the customer part of an MPLS
> network.
> All the label switching happens in the core of the MPLS network, and is
> intended to simulate a private dedicated IP cloud for each VPN.
> So - treat it like a private any to any IP net and ignore the MPLS label on
> the tin........
>
>
>
> > Actually, I got a detail wrong. Three of the sites (including the
> > main site) are connected through frame-relay, but the other ten are
> > connected through regular T1. I should point out that AT&T is the
> > vendor for most, but not all, of these local connections. The MPLS
> > network is pure AT&T.

>
> sounds like some of your sites have to go via a F/R access network to get to
> the MPLS cloud.
>
> a lot of carriers do this at lower density parts of the network since they
> have big F/R & ATM networks, they still work, and they are busy taking
> people off those direct services, so spare capacity is there.
>
> However - you often lose facilities if you go to MPLS via a "real" Frame or
> ATM cloud instead of just using it on the access point to point link - fewer
> or no QoS levels, and maybe limits to how full you can run the circuit.
>
> --
> Regards
>
> (E-Mail Removed) - replace xyz with ntl


Thanks. Whoever built out the network didn't leave any documentation,
and I'm trying to get contact info from my boss, but until then I'm
just sort of stuck at what looks to me like a very strange network
design.

 
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Ranak Ranak is offline
Junior Member
Join Date: Nov 2007
Posts: 2
 
      11-12-2007
Not to worry.

If anything, just worry about the circuits themselves. MPLS is more of a carrier-side configuration. That's the nice thing about MPLS, you can have Ethernet, Frame-Relay, ATM, etc. packets going in and it's pretty much transparent to you. The only thing that MPLS cares about is the shim header that it puts in your packet.

Labels are bound to routes in the routing table...
 
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