iBGP vs EIGRP

[louis0001]

We have 50 sites suplied via an ISP private MPLS network. Routing is BGP.

The 50 sites come into our 2 main sites A & B via this.

A & B are also directly connected via a PtP. We use EIGRP for the routing between these sites.

We readvertise our BGP remote sites into EIGRP. All is well.

To simplify things, I was thinking of doing away with EIGRP and replacing it with iBGP ie no readvertisement of BGP into EIGRP.

Just iBGP and eBGP.

Is there any downside with this?

[Seb Rupik]

Hi there,

Typically you would want to configure iBGP between your AS border routers, as it provides a method of sharing path attributes between them allowing for better route manipulation.

You should only redistribute into another IGP if there are routers placed further into your AS.

cheers,

Seb.

[balaji.bandi]

Technically good approach also in the future if you have non-cisco you can integrate directly with any hassle with iBGP.

Eigrp cisco properiatary (some vendor use to deploy, not many in real case).

In real world design if do not have many routues people prefer IGP rather IBGP.

Make sure you have local technical Skills for Managing the i/BGP. Other than that all 

Other note, this will be major change on your network, take long time to implment and test, if no issue in the network around now,  i stay with EiGRP, and if any upgrade or new sites coming or hardware upgrade or patch , i wil slowly move to iBGP. 

[louis0001]

Our whole network apart from the link between these two sites runs on BGP.

These two sites are the only sites that have EIGRP and that's only between the other routers that connect the sites directly.

Never say never, but these two sites probably won't expand much more so I'm hoping iBGP will be a good choice.

[paul driver]

Hello

Do/or will these two sites run in the same ASN?
Do they share the same networks?

if not then suggest to keep with an IGP,  As it is currently you can probably route between the two sites via their igp path and just use the bgp for external traffic and in case for failure of the p2p link use the bgp as a redundant path between sites , that if however your not doing this already?

[louis0001]

No, the sites are in a different private ASN as are all the other remote sites. Each site obviously has a router that runs BGP.

The difference with these two sites (A & B) is there are an additional router to connect each other together. These routers are the only routers in the network that run EIGRP. Nothing special going on apart from we readvertise the BGP routes into EIGRP so that if a new remote subnet is created, it is readvertised into these routers running BGP.

Prior to EIGRP, it was static routes and need manual intervention.

Rather than readvertise BGP into EIGRP, I just wanted to remove the EIGRP and deal soley with BGP (keep it tidy)

So basically, if a remote site was created, it would automatically be advertised to all routers with BGP.

If the router (connected to the ISP at SITE A) went down, remote sites would reroute via SITE B to get to site A and vice versa.

[paul driver]

Hello

Forgive but maybe i am not understanding your topology , you say each router in site A/B are indeed in different bgp ASN's? -  If so that rules out ibgp

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@louis0001 wrote:

A & B are also directly connected via a PtP. We use EIGRP for the routing between these sites.

We readvertise our BGP remote sites into EIGRP. All is well

the sites are in a different private ASN as are all the other remote sites. Each site obviously has a router that runs BGP.

The difference with these two sites (A & B) is there are an additional router to connect each other together. These routers are the only routers in the network that run EIGRP.

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Now given your statement above and if i understand this correctly , When a new site/subnet is brought on line that will site/subnet will get advertise into bgp anyway and both these routers will receive those new prefixes via their own respective bgp isp peering correct?

So why at present do you have a PTP eigrp between site A/B  for what reason - local access correct?

[louis0001]

Yes, the two sites (A & B) are our core sites and house all of our servers etc. Each is a DR for each other and uses the PtP for replication etc.

They are in different private ASN's so I was looking to replace the current setup which uses a stacked 3750x (layer 3) to route between sites (doesn't have an IP Avanced services license so no BGP)

I want to leave the 3750x in place and use it purely for layer 2 and place a new ISR 4431 at each end of the PtP link (which is currently using EIGRP for routing directly between the two sites)
If I do this, I can then use BGP (instead of redavertising BGP into EIGRP) as follows:

iBGP between SITE A (AS 61000) R1  & R3 (new ISR 4431 router)

iBGP between SITE B (AS 61001) R2  & R4 (new ISR 4431 router)

Both sites are in different ASN's so eBGP is used between the ISP provided private MPLS (AS 11111) and I want to discontinue EIGRP between the PtP and use eBGP for that. Adding the second BGP router at each site would use iBGP between itself and the existing router as they are both in the same AS.