Routing Protocol replacement

[mkannan_29]

Hi Experts,

I am having a clarification in BGP. Currently we are using BGP for Internal/External routing(IBGP/EBGP).

Can you help me on the below queries

1) whether I can use IBGP for External routing also

2) Planned to replace IBGP with OSPF

    I am having multiple office interconnected. So implementing OSPF with multiple areas will be the best option when compared to IBGP.

Cheers,

M.K

[Peter Paluch]

Hello,

I do not fully understand the way you are using the BGP. Nevertheless, let me try to answer some of your questions and let us see if that covers what you are interested in.

iBGP can not be used for external routing because by definition, an iBGP session is established between two BGP speakers in the same AS, and an eBGP session is established between BGP peers in different AS systems. You can not control whether the peering will be iBGP or eBGP, as it depends purely on the AS numbers of the peers and this distiction is made internally by BGP - without you being able to do something about it.

Regarding replacing the iBGP with OSPF - that suggests that currently, you are running BGP on all your routers. Is that correct? Please note that, depending on your routing policy, you will still have to keep iBGP running between your autonomous system boundary routers.

It would probably help if you described in more detail the routing policy inside your network and perhaps included a network exhibit clarifying how the routing is done.

Best regards,

Peter

[mkannan_29]

Hi Peter,

Thanks for the revert on iBGP.

Same AS  ---> iBGP

Different AS ---> eBGP

Enclosed the diagram for my current setup. Planning to replace iBGP with OSPF.

[shehinpm1]

Hi,

As long as you hv multiple link to ISP better to keep IBGP peering b'n branch routers inorder to get link redundancy .i cant see any advantage changing from ibgp to ospf.in case if u r using ospf u wl hv to redistrubute this route in to bgp.

BR,

shehin.pm

[Peter Paluch]

Hello,

I agree with Shenin. Do you have any particular reason to remove the iBGP peerings between your CE routers and replace it with OSPF?

Best regards,

Peter

[mkannan_29]

hi,

As we want to redesign the IGP. So that I have selected OSPF as the best option.

Under OSPF each branch office will be configured as an area.

as per the exisitng setup we'll have 4 areas and one backbone area to be configured(Head office will be used as BB)

planning to configure OSPF as Hub and Spoke design.

We need to disable iBGP & OSPF to be configured for routing between the branch offices.

please let me know the suggestions for the same.

Regards,

M.K

[Peter Paluch]

Hello,

I would personally retain the iBGP peering between the CE routers, along with activating the OSPF towards the remained of the branch, assuming there is at least one more C (i.e. customer internal) router.

What exactly are you interested in asking about running the OSPF? There is nothing exceedingly special about this deployment. You simply run OSPF+BGP on CE routers, and redistribute the OSPF into BGP. In the backward direction, you may either choose to redistribute BGP into OSPF, or just generate a default route into the OSPF domain depending on your needs.

I am not sure about the hub and spoke design. The MPLS VPN in the middle will provide you with fully meshed branch-to-branch connectivity. Is there any particular reason for the hub and spkoe?

Best regards,

Peter