BGP Redundancy on two different setup

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Oct 6th, 2008
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Hi,


Currently i have ISP setup which is running in active/pasive mode means.


I have four router

1).Two Router in Core -OSPF & IBGP

2).Two router in Distribution--OSPF & IBGP


Core RoutCore Router-1 is having LP-300 so incoming will be prefereed from Core Router-1 & for outgoing we had set injected defualt toute with riginate metric 2 metric-type 1 so outgoing will from Core route-1 only.

Core RoutCore Router-2 is having LP-200 so incoming will be prefereed if Core Router-1 is down.& for outgoing we had set injected defualt toute with riginate metric 10 metric-type 1.


Setup is running succesfully & we had been told to setup parrelll setup wich will have differnet set of customer & in case any problem they need to be automatically taken care to announce on from Setup-1.


I was thinking to setup same as Setup but if i run OSPF on both the setup then prefered outgoing will from Setup-1 due to defualt route.


Kindly suggest best possible way of setting up IBGP with upsteam & downsteam(Setup-1 & setup-2)


I am attaching the setup-1 configuration with setup --1 & Setup--2 Diagram.


regards,




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Giuseppe Larosa Mon, 10/06/2008 - 22:50
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Hello Moorthy,

>> I was thinking to setup same as Setup but if i run OSPF on both the setup then prefered outgoing will from Setup-1 due to defualt route.


using O E1 routes the internal metric is added to external seed metric so you can replicate the config of Setup1 in Setup2 on OSPF links between Setup1 and Setup2 use ip ospf cost 500 this should be enough to have users of Setup2 to point to routers of Setup 2.

Set ip ospf cost in both directions

This should help also with iBGP because when L-P is equal they go on in comparison and look for IGP metric to BGP next hop.


Hope to help

Giuseppe


moorthy1977 Wed, 10/08/2008 - 02:23
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Dear Giuseppe,


Thanks for providing the information.


Still some doubts.


1.Whether i need to keep same bgp cluster-id on setup-1 & setup-2.

2.If i connect Distibution switch setup-1 SP1-D1 & SP1-D2 to Core Router setup-2 SP1-G1 & SP1-G2 respectively & set ospf to 500 & vice versa on setup-2 will it work.


If i set above setup then what will be the memory utlization will it work with 7609 with 3CXL supervisior enginre with full bgp + IBGP routes(internal /29 of above routes injected in difeernet location).




Regards,


Giuseppe Larosa Wed, 10/08/2008 - 05:20
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Hello Moorthy,


1) use different cluster-id on the two setups or cluster to cluster iBGP reflection will not work correctly : Cluster-id is placed in the BGP attribute cluster-list by route-reflector the receiving route-reflector on other setup will check the cluster-list if sees its own it will think the BGP advertisement has been already processed and will ignore it.


2) you need to rise OSPF costs on both side of each inter-setup link it is the only way to create two zones of influence for the O E1 default routes but depending on topology other paths can exist between the two setups.


3)

You should be fine with sup 3CXL up to 3-4 full BGP tables from different providers


Hope to help

Giuseppe


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