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alex_rhys-hurn
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BGP Noob: balance and failover on WAN not ISP

Thu Apr 01, 2010 10:03 pm

Hello,

I am new to BGP but not OSPF and Mikrotik. I would like a few tips from the BGP pros out there if you dont mind.

OSPF will do failover but not load balance with failover, so I want to use BGP.

The BGP Failover and load balancing that I have seen in the forums so far relate to interfacing with ISPs.

I do not want to do this with an external ISP but on my own WANs.

I have 7 sites dotted around the country. Each site is connected with a LAYER 2 FIBER WAN service provided by two separate Fibre Companies.

So I can do any IP addresing or private AS Numbers that I want, but I am not sure what the overall steps to consider with putting BGP on this so that load is balanced and failed properly.

Some overview pointers would help. (I am still reading some heavy stuff in the WIKI and on Cisco Press as well).

Thank you,

Alex
 
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roadrunner
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Re: BGP Noob: balance and failover on WAN not ISP

Fri Apr 02, 2010 9:08 am

I currently use OSPF for load balancing with fail-over. Just set all the paths to have the same OSPF cost. This is easy with parallel links and each end going into the same router. It is a more difficult but still possible with asymmetric links with multiple routers.

Inside the a network, to load balance I normally use MultiPath (ECMP) routes http://wiki.mikrotik.com/wiki/Manual:IP/Route. It requires the main routing table to have the same route multiple times with a different gateway/next-hop on each one -. This can be done using static routing or OSPF, I do not think BGP can add more than one route into the IP routing table for each destination.
 
alex_rhys-hurn
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Re: BGP Noob: balance and failover on WAN not ISP

Fri Apr 02, 2010 11:47 am

Hi Roadrunner,

Thanks for the info. Of course I forgot about ECMP....

How well will this work on links that do not have the same bandwidth?

One provider gives me a 10mbit cloud (bandwidth is shared by all sites in the cloud and the other is giving dedicated bandwidths per site, and they all vary. This is presumably what you meant by asymmetric links.

The plus is that at each site both links are terminated in the same router. RB1000 at HQ and RB450G at each site.

Alex
 
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Re: BGP Noob: balance and failover on WAN not ISP

Fri Apr 02, 2010 12:47 pm

I was meaning multiple hops and routers on one path and 1 hop to go through on the other path, this would make you adjust interface cost on many links to get them to balance. Two unequal speed links can be just as troublesome.

For your unequal setup, you either live with the faster links being under utilized, or setup multiple parallel paths or tunnels over the faster links. If you have a clean ethernet connection between your rb1000 and the remote 450G routers, just create multiple vlans and load balance over each of those vlans.

But if the faster links are all faster than the cloud connection, perhaps you should just use the cloud as the backup. Alternately you could choose 1 site that needs a bit more speed and only load balance that site using the cloud, all the other sites use the cloud as a backup link.

This type of load balancing is not perfect, each download/upload will be limited to the speed of the link it is on. In other words this will not bond the multiple paths into one big connection.
 
alex_rhys-hurn
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Re: BGP Noob: balance and failover on WAN not ISP

Fri Apr 02, 2010 1:43 pm

OK, I read you load and clear.

My head is now in to this. It hadnt occurred to me that I could create extra paths by creating tunnels or vlans.

I am going to try that! Thanks.

Alex
 
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Re: BGP Noob: balance and failover on WAN not ISP

Fri Apr 02, 2010 7:55 pm

i dont think you can do load balancing with bgp, just failover. two or more routes with the same prefix properties, and only one will be active.
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Re: BGP Noob: balance and failover on WAN not ISP

Sat Apr 03, 2010 8:42 pm

You can loadbalace via bgp, you just have to work for it. You can prepend and use path atributes such as local preference. It can be a bit of am art. I would agree with ECMP ospf, though :)
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Re: BGP Noob: balance and failover on WAN not ISP

Tue Apr 06, 2010 11:28 am

To create multipath routes with BGP, use multiple recursive next-hop resolution (http://wiki.mikrotik.com/wiki/Manual:BG ... interfaces), or use "set-in-nexthop" filter.

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