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about interdomain multipath routing.

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bin.danieldai at gmail

Nov 9, 2009, 5:56 PM

Post #1 of 9 (703 views)
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about interdomain multipath routing.

Hi:
These days, in the research, the interdomain multipath routing is
pretty hot but i doubt its actually use in reality.
Does anyone tell me any use of interdomain multipath routing like
multipath BGP in the real world?

Best,
Daniel

sking at kingrst

Nov 9, 2009, 7:30 PM

Post #2 of 9 (668 views)
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Re: about interdomain multipath routing. [In reply to]

We use eBGP multipath where I work. We usually get two or more
connections to each provider we have. Using multipath we are able to add
hardware redundancy with bandwidth balancing (to an extent) with this
method. There are some providers who will only allow multipath eBGP and
not even let you run multihop eBGP.

Bin Dai wrote:
> Hi:
> These days, in the research, the interdomain multipath routing is
> pretty hot but i doubt its actually use in reality.
> Does anyone tell me any use of interdomain multipath routing like
> multipath BGP in the real world?
>
> Best,
> Daniel
>

--
Steve King

Network Engineer - Liquid Web, Inc.
Cisco Certified Network Associate
CompTIA Linux+ Certified Professional
CompTIA A+ Certified Professional

mpetach at netflight

Nov 9, 2009, 7:50 PM

Post #3 of 9 (667 views)
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Re: about interdomain multipath routing. [In reply to]

On Mon, Nov 9, 2009 at 5:56 PM, Bin Dai <bin.danieldai [at] gmail> wrote:
> Hi:
> These days, in the research, the interdomain multipath routing is pretty hot
> but i doubt its actually use in reality.
> Does anyone tell me any use of interdomain multipath routing like multipath
> BGP in the real world?

I've outlawed the use of multihop eBGP for load-sharing here; when we get
multiple links off the same router to a peer or upstream, they are configured
with multipath. We've got hundreds of BGP sessions across the network
configured with multipath on them.

Matt

> Best,
> Daniel
>
>

jbates at brightok

Nov 9, 2009, 8:16 PM

Post #4 of 9 (665 views)
Permalink

Re: about interdomain multipath routing. [In reply to]

Matthew Petach wrote:
>
> I've outlawed the use of multihop eBGP for load-sharing here; when we get
> multiple links off the same router to a peer or upstream, they are configured
> with multipath. We've got hundreds of BGP sessions across the network
> configured with multipath on them.
>

Same here for my connections, though some of my customers are stuck with
multihop eBGP in certain remote areas, but that's a completely different
scenario (single link, but obsolete equipment) and out of my control.

I much prefer multipath, especially given that the standard multihop
config uses static routing and there are conditions that could cause the
flap of the eBGP session during a single link outage. With Multipath,
only the effected path goes down, as it should.

Jack

sking at kingrst

Nov 9, 2009, 8:22 PM

Post #5 of 9 (675 views)
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Re: about interdomain multipath routing. [In reply to]

Those are very good points Jack. We stopped using multihop for those
same reasons.

Jack Bates wrote:
> Matthew Petach wrote:
>>
>> I've outlawed the use of multihop eBGP for load-sharing here; when we
>> get
>> multiple links off the same router to a peer or upstream, they are
>> configured
>> with multipath. We've got hundreds of BGP sessions across the network
>> configured with multipath on them.
>>
>
> Same here for my connections, though some of my customers are stuck
> with multihop eBGP in certain remote areas, but that's a completely
> different scenario (single link, but obsolete equipment) and out of my
> control.
>
> I much prefer multipath, especially given that the standard multihop
> config uses static routing and there are conditions that could cause
> the flap of the eBGP session during a single link outage. With
> Multipath, only the effected path goes down, as it should.
>
>
> Jack
>

--
Steve King

Network Engineer - Liquid Web, Inc.
Cisco Certified Network Associate
CompTIA Linux+ Certified Professional
CompTIA A+ Certified Professional

kloch at kl

Nov 9, 2009, 8:23 PM

Post #6 of 9 (664 views)
Permalink

Re: about interdomain multipath routing. [In reply to]

Bin Dai wrote:
> Hi:
> These days, in the research, the interdomain multipath routing is pretty
> hot but i doubt its actually use in reality.
> Does anyone tell me any use of interdomain multipath routing like
> multipath BGP in the real world?

"BGP multipath" is extremely common and used to load balance multiple
links to the same neighbor ASN. As implemented by popular vendors it
requires most attributes (like as-path) to be identical.

Did you really mean this or something that uses different as-paths
in parallel?

- Kevin

laned1 at gmail

Nov 10, 2009, 1:10 AM

Post #7 of 9 (663 views)
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Re: about interdomain multipath routing. [In reply to]

On Tue, Nov 10, 2009 at 3:50 AM, Matthew Petach <mpetach [at] netflight> wrote:
> I've outlawed the use of multihop eBGP for load-sharing here; when we get
> multiple links off the same router to a peer or upstream, they are configured
> with multipath. �We've got hundreds of BGP sessions across the network
> configured with multipath on them.
>

Do you use iBGP multipath as well to load-balance between links on
different routers?

I know eBGP multipath is fairly common, but I wonder how many are
using iBGP multipath as well. I doubt any carriers would support it,
so it's probably only useful for load-balancing outbound traffic. The
problem with eBGP multipath alone is that you might want to terminate
circuits from a given carrier on two different routers for redundancy
reasons, but that precludes any load-balancing with eBGP multipath.
Obviously your network has to be designed with equal-cost paths for
iBGP multipath to be of any value.

-Doug

mpetach at netflight

Nov 10, 2009, 1:23 AM

Post #8 of 9 (657 views)
Permalink

Re: about interdomain multipath routing. [In reply to]

On Tue, Nov 10, 2009 at 1:10 AM, Doug Lane <laned1 [at] gmail> wrote:
> On Tue, Nov 10, 2009 at 3:50 AM, Matthew Petach <mpetach [at] netflight> wrote:
>> I've outlawed the use of multihop eBGP for load-sharing here; when we get
>> multiple links off the same router to a peer or upstream, they are configured
>> with multipath. �We've got hundreds of BGP sessions across the network
>> configured with multipath on them.
>>
>
> Do you use iBGP multipath as well to load-balance between links on
> different routers?

Yes.

> I know eBGP multipath is fairly common, but I wonder how many are
> using iBGP multipath as well. I doubt any carriers would support it,
> so it's probably only useful for load-balancing outbound traffic. The
> problem with eBGP multipath alone is that you might want to terminate
> circuits from a given carrier on two different routers for redundancy
> reasons, but that precludes any load-balancing with eBGP multipath.
> Obviously your network has to be designed with equal-cost paths for
> iBGP multipath to be of any value.
>
> -Doug

iBGP with multipath, multiple LSPs to each BGP next-hop...much load
balancing across all same-cost internal links to each of the eBGP
multihop next-hops.

inet.0: 300787 destinations, 2675963 routes (300092 active, 2
holddown, 2086 hidden)

Yes...takes up a chunk more memory keeping track of all the
different paths, but it does provide more end-to-end load balancing
of traffic even on different routers.

Matt

sking at kingrst

Nov 10, 2009, 11:13 AM

Post #9 of 9 (635 views)
Permalink

Re: about interdomain multipath routing. [In reply to]

We use multipath setups for our EIGRP and iBGP configurations for our
internal routing as well. Although for larger networks iBGP multipath
might be of use due to memory limitations on a lot of devices.

Doug Lane wrote:
> On Tue, Nov 10, 2009 at 3:50 AM, Matthew Petach <mpetach [at] netflight> wrote:
>
>> I've outlawed the use of multihop eBGP for load-sharing here; when we get
>> multiple links off the same router to a peer or upstream, they are configured
>> with multipath. We've got hundreds of BGP sessions across the network
>> configured with multipath on them.
>>
>>
>
> Do you use iBGP multipath as well to load-balance between links on
> different routers?
>
> I know eBGP multipath is fairly common, but I wonder how many are
> using iBGP multipath as well. I doubt any carriers would support it,
> so it's probably only useful for load-balancing outbound traffic. The
> problem with eBGP multipath alone is that you might want to terminate
> circuits from a given carrier on two different routers for redundancy
> reasons, but that precludes any load-balancing with eBGP multipath.
> Obviously your network has to be designed with equal-cost paths for
> iBGP multipath to be of any value.
>
> -Doug
>
>

--
Steve King

Network Engineer - Liquid Web, Inc.
Cisco Certified Network Associate
CompTIA Linux+ Certified Professional
CompTIA A+ Certified Professional

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