Replacing Point-Point T1 with MPLS Managed Circuit

Answered Question
Feb 28th, 2010
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RouterA and RouterB are both running ospf as their IGP. My company has decided to replace the point to point t1 with a managed mpls circuit.

According to the new provider it should transparent and will just be an ”Ethernet handoff. " Question: what do I configure on RouterA to connect through the mpls cloud over to RouterB? Do I configure ebgp and perform bi-directional redistribution? Do I create a GRE tunnel from RouterA to RouterB?

Sorry, connectivity through a managed mpls provider cloud is new to me. Thanks in advance.



Correct Answer by paolo bevilacqua about 7 years 2 months ago

Ethernet handoff should mean you will have L2 connectivity.

Even if it is not that (L3 MPLS), it is not said you will have to configure BGP or other routing protocols to them.


Ask your SP for a detailed axplaination of the service given.

Correct Answer by KARUPPUCHAMY MA... about 7 years 2 months ago

Hi,


Yes.. we need to redistribute BGP routes into IGP so that Lcation B Networks will be reachable via BGP and vice versa.


The best way to advertise the network into MPLS cloud is use network command instead of redistributing into BGP.


Redistribute BGP routes into OSPF, But advertise the OSPF routes into BGP via "Network" Command.


Example : Advertise Location A network into BGP via network command at the same device redistribute BGP routes into OSPF, The same thing vice vera in Location B side.


As per BGP rule, the network which we are advertising into BGP, that should be reachable via IGP then only that route will be installed into BGP routing table else it will be in BGP table not into BGP Routing Table.


so the traffic flow from Location A to Location B is like this


User Location A  ---(IGP)--- > CE(A side)--- Look up Destination in BGP Routing Table ---> MPLS CLoud --- > CE(B Side) --- (IGP) --- > User Location B.


Regards

Karuppu

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KARUPPUCHAMY MA... Sun, 02/28/2010 - 21:56
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Hi,


Better to have MPLS instead of P2P Link


Since you are going to buy MPLS link, they will provide one /30 IP address for your one side location(Router A - CE IP address) and the same another /30 IP address they will provide for your another Location and they will let you know their /30 IP address as well (PE IP address)


CE - Customer Edge that is your IP address , PE - Provider Edge that is Service Provider IP address


Now you have to replace with your OSPF  into BGP.


Router A  --(eBGP)-- > Service Provider (A Side) ----(MPLS Cloud)----> Service Provider(B Side) ---(eBGP)---> Router B


You need to configure eBGP between your Router A(CE) to Service Provider(A) and Router B(CE) to Service Provider(B) then advertise your network into the MPLS cloud via your BGP .


Sample Config:


router bgp 12345(your private AS number)
no synchronization
bgp log-neighbor-changes
network 10.10.0.0 mask 255.255.0.0  // advertising your network into MPLS cloud//
network 10.46.202.0 mask 255.255.255.0
neighbor remote-as
no auto-summary


regards

Karuppu

Correct Answer
KARUPPUCHAMY MA... Sun, 02/28/2010 - 22:10
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  • Silver, 250 points or more

Hi,


Yes.. we need to redistribute BGP routes into IGP so that Lcation B Networks will be reachable via BGP and vice versa.


The best way to advertise the network into MPLS cloud is use network command instead of redistributing into BGP.


Redistribute BGP routes into OSPF, But advertise the OSPF routes into BGP via "Network" Command.


Example : Advertise Location A network into BGP via network command at the same device redistribute BGP routes into OSPF, The same thing vice vera in Location B side.


As per BGP rule, the network which we are advertising into BGP, that should be reachable via IGP then only that route will be installed into BGP routing table else it will be in BGP table not into BGP Routing Table.


so the traffic flow from Location A to Location B is like this


User Location A  ---(IGP)--- > CE(A side)--- Look up Destination in BGP Routing Table ---> MPLS CLoud --- > CE(B Side) --- (IGP) --- > User Location B.


Regards

Karuppu

davidhuynh5 Tue, 03/02/2010 - 18:07
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Thanks Karuppu. What if the ISP gave me one single AS# for all my sites.

Will I need to run iBGP? Is it even neccessary? I just want the prefixes on RtrA to be seen on RtrB and vice versa so that they can communicate with each other.

Correct Answer
paolo bevilacqua Mon, 03/01/2010 - 04:20
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Ethernet handoff should mean you will have L2 connectivity.

Even if it is not that (L3 MPLS), it is not said you will have to configure BGP or other routing protocols to them.


Ask your SP for a detailed axplaination of the service given.

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