better routing protocol

Unanswered Question
Jun 4th, 2009

Hi,

We have a site with a central switch conneccting to two different uplink providers through 2 different routers.

Keen to run dynamic protocol between ports connecting these 3 components, ospf or eigrp preferred. Help to know which would server following purpose & Why.

1.Outbound loadsharing of traffic.

2.Redundancy failover to other link in case of failures.

Properiety nature of protocol can be excluded from the discussion.

Thanks.

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sachinraja Thu, 06/04/2009 - 06:49

Hello Sunny

Do you want to run the dynamic routing protocol over the 2 ISPs or on the LAN side ? If we are talking about configuring it over the WAN, are the ISP's routing your public IP traffic, or is it a VPN carrier ? I mean do the sites end to end look like a point to point link ? If you want to do multihoming, then you need to consider BGP.. If we are restricting the post to LAN or point to point routing, then go for EIGRP (considering you have cisco devices).. EIGRP has many advantages over OSPF including better convergence, summarization/route filtering at any boundary, unequal path loadbalancing etc.. there are lots of docs on internet comparing these protocols..

again to answer to your questions:

1.Outbound loadsharing of traffic - possible with BGP/EIGRP.. outbound is more controlled by you..

2.Redundancy failover to other link in case of failures. - possible..

Hope this helps.. all the best.. rate replies if found useful..

Raj

sachinraja Thu, 06/04/2009 - 06:50

Hello Sunny

Do you want to run the dynamic routing protocol over the 2 ISPs or on the LAN side ? If we are talking about configuring it over the WAN, are the ISP's routing your public IP traffic, or is it a VPN carrier ? I mean do the sites end to end look like a point to point link ? If you want to do multihoming, then you need to consider BGP.. If we are restricting the post to LAN or point to point routing, then go for EIGRP (considering you have cisco devices).. EIGRP has many advantages over OSPF including better convergence, summarization/route filtering at any boundary, unequal path loadbalancing etc.. there are lots of docs on internet comparing these protocols..

again to answer to your questions:

1.Outbound loadsharing of traffic - possible with BGP/EIGRP.. outbound is more controlled by you..

2.Redundancy failover to other link in case of failures. - possible..

Hope this helps.. all the best.. rate replies if found useful..

Raj

Richard Burts Thu, 06/04/2009 - 06:54

Sunny

If your site has only a central switch and 2 routers then I believe that there is very little to choose between OSPF and EIGRP. They will both work very well in that situation. I believe that they will do equally well in loadsharing of outbound traffic and on redundancy in case of failure.

It is probably more important to work out how the routers will generate a default route and advertise it which is the basic requirement for outbound load sharing. And there may be questions of how the router will recognize that it needs to withdraw its default route (how will it recognize failure) which is the basic requirement for redundancy in case of failure.

HTH

Rick

suthomas1 Thu, 06/04/2009 - 07:06

the routing protocol is intended to run solely for facilitating proper outbound loadbalancing. This site is connected via carrier to our HQ. But the routing protocol will not be extended over the cloud to other side,i.e no exchange of dynamic routes intended between both locations.

sachinraja Thu, 06/04/2009 - 07:20

Sunny

It really doesnt matter then.. you can use any protocol as Rick mentioned.. but the point here is, do you need routing protocols here ? Cant do off dual static routes on the core switch, or use something like policy routing, or specific route mappings ? Again, outbound traffic flow is entirely controlled by the local router, and you can use any of the techniques given above.

Raj

suthomas1 Thu, 06/04/2009 - 07:25

by outbound loadsharing, it is intended that both links be used simultaneously atleast to some extent.I weighed PBR & other options, but that would mean diverting specific flows to specific links which our architecture doesn't permit.

NOw, comparing...wouldnt eigrps unequal feature be of no use here as we are looking at equal loadsharing & i believe ospf would do it by itself.

Please correct, if am wrong.

Thanks

lroberson Thu, 06/04/2009 - 08:53

You mention uplink providers? If this are ISP then you should use BGP and they should supply you BGP. You can get full or partial table updates from your providers. BGP will provide best routing path. You can also configure BGP metrics to modify path selections. You also want to make sure that you are not a pass through for the providers in the advent of a provider goes off the network backbones.

Joseph W. Doherty Thu, 06/04/2009 - 10:01

Both OSPF and EIGRP can be used for equal cost load sharing, as can statics. EIGRP also supports varible cost load sharing. Dynamic routing protocols tend to deal well with failures, statics less so, although with Cisco's latest object tracking, they can too.

For routing load sharing it's, more-or-less round robin per flow unless you have packet-by-packet load sharing, which can lead to packet sequencing issues (somthing we often want to avoid).

Cisco latest IOSs also support a new technology, OER/PfR, which can both dynamically load balance and provide best possible performance to flows. Older versions are limited to BGP or statics, latest version support any(?) routing protocol.

suthomas1 Thu, 06/11/2009 - 04:21

I wont be resorting to packet loadsharing to keep sequence issues out.My scenario involves just four interfaces alltogether for enabling routing protocol.Bgp is excluded from this.Looking at ospf & eigrp, how would each weigh over other in achieving outbound loadsharing & resiliency or switchover in case of failures.

Any pros or cons would be helpful for me to decide .

Thanks.

Joseph W. Doherty Thu, 06/11/2009 - 04:51

"Looking at ospf & eigrp, how would each weigh over other in achieving outbound loadsharing & resiliency or switchover in case of failures. "

For just those issues, probably they're close enough that other issues would determine the selection.

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