Best option to have load balancing and automatic failover with 2 symmetric MPLS links

[walter.perera]

Hi all:

We have a couple of symmetric MPLS links connected  with 4 routers on two different countries. Each pair of routers located  in the same countries have L2 connectivity. The MPLS works with BGP.

We  are looking for the best option to have load balancing and automatic  failover. We tried with GLBP and IP SLA, but it seems that it is not 100% suitable  for our purposes (for instance, it takes around 3 mins when one of the WAN links is down)

Most of the traffic goes from country A to country B.

Ideas?

Thanks!

[Giuseppe Larosa]

Hello Walter,

>> it takes around 3 mins when one of the WAN links is down

this is very close to default BGP hold timer of 180 seconds you should use per session timers like 5 seconds hello 15 seconds hold time to improve convergence.

router bgp

neighbor x.x.x.x timer 5 15

From a routing point of view assuming you have eBGP sessions with providers all you need is an iBGP session between co located routers

Hope to help

Giuseppe

[walter.perera]

Hi Giuseppe:

Thanks for replying!

We may try that one. I believe co-located (i hope you mean in the same country) routers are only using GLBP and not iBGP.

Questions regarding this:

1. Would iBGP be required? In our internal LAN (Country A), we have only static routing.

2. Apart from GLBP, is there another (better) option to implement load balancing and automatic failover?

Thanks

[Giuseppe Larosa]

Hello Walter,

an iBGP session between routers in the same country is highly recommended to improve network convergence, It provides backup routes that will be used only in case of failure.

The use of BGP timers is effective as you will see in your tests.

GLBP is good when there are multiple clients connected directly to the routers, but GLBP is NOT a routing protocol it provides first hop redundancy

Here, it is question of choice I would use iBGP instead of static routes with added intelligence of IP SLA and object tracking.

Each router would still prefer eBGP routes over routes learned via the iBGP session.

As noted by Joseph, other solutions using OER/PfR are possible.

But you are already using BGP with MPLS providers so tuning BGP that would still be used is a good way to go.

Hope to help

Giuseppe

[Joseph W. Doherty]

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Posting

If your platforms support it, OER/PfR is a possible option to dynamically load balance.

[walter.perera]

Hi Giusseppe and Joseph,

Thanks again!

So the 2 options here are:

1. Implement iBGP in the 4 routers

2.OER/PfR

Some questions:

1. We manage the 4 routers, but only one LAN (country A). Do you think there could be a problem using iBGP. One more thing to consider is that we are NATing from Country A routers when going to Country B Networks, so it is consuming resources as well. Given that scenario, would be still feasible to implement iBGP?

2. Regarding OER / PfR, is there some link to good documentation on this?

thanks!

Message was edited by: Walter Perera

[Giuseppe Larosa]

Hello Walter,

I was meaning one iBGP session between RA1 and RA2 and one iBGP session between RB1 and RB2.

If the BGP sessions carry only internal networks ( no internet full table) for site to site connectivity there shouldn't be any issue in adding the two iBGP sessions. A client facing Vlan may be used for the iBGP session, there is no need of a dedicated link.

>> One more thing to consider is that we are NATing from Country A routers when going to Country B Networks

So you are combining NAT with GLBP. Do you use a form of stateful NAT ?

Hope to help

Giuseppe

[walter.perera]

Hi Giussepe

We are using stateful NAT in routers A

If we use iBGP, we would need to have another router in country A, and enable iBGP there as well, in order to work as single point of connection to that MPLS links, or should we use GLBP?

Also, we could not advertise the networks on Routers B as we do not manage them.

Thanks

[Giuseppe Larosa · Accepted solution]

Hello Walter,

you don't need any additional router just to run an iBGP session between the two existing routers in country A.

Hope to help

Giuseppe

[Joseph W. Doherty · Accepted solution]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

2. Regarding OER / PfR, is there some link to good documentation on this?

You might start here: http://www.cisco.com/en/US/products/ps8787/products_ios_protocol_option_home.html