Re: How to adjust the "traffic share count/ratio" of equal cost IGP path ?

From: Yu Ning (yuning@cndata.com)
Date: Wed Sep 27 2000 - 07:06:17 EDT


Hi Chris,

Thanks your patient and detailed answer, but I already know it, and it's not
related with what I've asked,:-) I know we can achieve it via MPLS, or BGP.
What I want to know, if you really have a detail look to my original message
is in the normal IGP enabled with CEF condition.

thanks anyway.

Yu Ning.
------------------------------------------
(Mr.) Yu(2) Ning(2)
Support,Int'l/Domestic Routing
ChinaNET(AS4134) Backbone Operation
Beijing,P.R.C. +86-10-66418105/8121/8122
------------------------------------------
----- Original Message -----
From: "Martin, Christian" <cmartin@gnilink.net>
To: "'Yu Ning'" <yuning@cndata.com>; "Andy Li" <ali@cisco.com>; <cisco-nsp@puck.nether.net>
Cc: "Chinanet-vt" <Chinanet-vt@cisco.com>
Sent: Tuesday, September 26, 2000 7:38 PM
Subject: RE: How to adjust the "traffic share count/ratio" of equal cost IGP path ?


> Yu,
>
> The router, in general, is attempting to find one and only one path to a
> destination - the best path. If all things are equal in regards to the
> particular protocols path selection algorithm, then a Cisco will
> load-balance among up to 6 equal cost paths. If your links are of different
> bandwidth/delay/cost - if their metrics differ, then they should not be part
> of this equal cost balancing, because they violate the very premise of
> equality itself. This is why IGPs do not allow for very robust traffic
> engineering. BGP can do a little more, but the configuration nightmare is
> to be avoided. This brings us to MPLS.
>
> In a nutshell, MPLS allows one to choose an arbitrary path through the
> network that uses an arbitrary (acyclic) sequence of node,link pairs to form
> a Label Switched Path. You can choose the path based on an administrative
> 'color', the amount of bandwidth needed, the level of QoS based on IP ToS,
> etc. Since the LSPs are set up before traffic flows, and because Label
> Switching Routers merely have to look up label mappings in a table, the
> forwarding is fast - even when only partially hardware accelerated - at all
> available interface speeds. In the Cisco world, there is still some legacy
> nomenclature (Tag Switching), but there is full support for MPLS, and it
> interpoerates well with Juniper (although jnpr does MPLS better - no fast
> reroute in Cisco yet.)
>
> If you don't want to use EIGRP, then look at MPLS. It may help you out a
> bunch.
>
> ./chris
>
> -----Original Message-----
> From: Yu Ning [mailto:yuning@ns.chinanet.cn.net]
> Sent: Tuesday, September 26, 2000 1:38 AM
> To: Andy Li; cisco-nsp@puck.nether.net
> Cc: Chinanet-vt
> Subject: Re: How to adjust the "traffic share count/ratio" of equal cost IGP
> path ?
>
>
> Hi Andy,
>
> Here is the result:
>
> rtr4-c-1-bjbj#sh ip cef 202.97.9.60
> 202.97.9.60/30, version 35751988, per-destination sharing, 0 packets, 0
> bytes
> via 202.97.9.17, POS2/0, 21 dependencies
> traffic share 1
> next hop 202.97.9.17, POS2/0
> valid adjacency
> via 202.97.9.161, POS2/3, 21 dependencies
> traffic share 1, current path
> next hop 202.97.9.161, POS2/3
> valid adjacency
> via 202.97.10.173, ATM4/1.1, 22 dependencies
> traffic share 1
> next hop 202.97.10.173, ATM4/1.1
> valid adjacency
> 0 packets, 0 bytes switched through the prefix
>
> rtr4-c-1-bjbj#sh ip cef 202.97.9.60 int
> 202.97.9.60/30, version 35751988, per-destination sharing, 0 packets, 0
> bytes
> via 202.97.9.17, POS2/0, 21 dependencies
> traffic share 1
> next hop 202.97.9.17, POS2/0
> valid adjacency
> via 202.97.9.161, POS2/3, 21 dependencies
> traffic share 1, current path
> next hop 202.97.9.161, POS2/3
> valid adjacency
> via 202.97.10.173, ATM4/1.1, 22 dependencies
> traffic share 1
> next hop 202.97.10.173, ATM4/1.1
> valid adjacency
>
> 0 packets, 0 bytes switched through the prefix
> Load distribution: 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 (refcount 65)
>
> Hash OK Interface Address Packets
> 1 Y POS2/0 point2point 0
> 2 Y POS2/3 point2point 0
> 3 Y ATM4/1.1 point2point 0
> 4 Y POS2/0 point2point 0
> 5 Y POS2/3 point2point 0
> 6 Y ATM4/1.1 point2point 0
> 7 Y POS2/0 point2point 0
> 8 Y POS2/3 point2point 0
> 9 Y ATM4/1.1 point2point 0
> 10 Y POS2/0 point2point 0
> 11 Y POS2/3 point2point 0
> 12 Y ATM4/1.1 point2point 0
> 13 Y POS2/0 point2point 0
> 14 Y POS2/3 point2point 0
> 15 Y ATM4/1.1 point2point 0
> 16 Y POS2/0 point2point 0
>
> Just like in the "sh ip ro", all the three links have equal share of the
> traffic.
> Because of them is ATM PVC, can I set him to share a small amount of traffic
> ?
> Unequal share ? Note we'd not use MPLS tunnel tricks.
>
> regards,
>
> ------------------------------------------
> (Mr.) Yu(2) Ning(2)
> Support Engineer, Int'l/Domestic Routing
> ChinaNET (AS4134) Backbone Operation
> Beijing, P.R.C. +86-10-66418105/8121/8122
> ------------------------------------------
> ----- Original Message -----
> From: "Andy Li" <ali@cisco.com>
> To: "Yu Ning" <yuning@ns.chinanet.cn.net>; <cisco-nsp@puck.nether.net>
> Cc: "Chinanet-vt" <Chinanet-vt@cisco.com>
> Sent: Monday, September 25, 2000 11:56 PM
> Subject: RE: How to adjust the "traffic share count/ratio" of equal cost IGP
> path ?
>
>
> > Please give theo utput of the following command
> >
> > sh ip cef 202.97.9.60
> >
> > Thanks
> > Andy
> >
> > -----Original Message-----
> > From: Yu Ning [mailto:yuning@ns.chinanet.cn.net]
> > Sent: Monday, September 25, 2000 12:21 AM
> > To: cisco-nsp@puck.nether.net
> > Cc: Chinanet-vt
> > Subject: How to adjust the "traffic share count/ratio" of equal cost IGP
> > path ?
> >
> >
> > Hi All,
> >
> > We know that if we see equal cost IGP routes, the Cisco box will load
> > balance between
> > the different output interfaces. For example:
> >
> > Routing entry for 202.97.9.60/30
> > Known via "isis", distance 115, metric 5, type level-2
> > Redistributing via isis
> > Last update from 202.97.10.173 on ATM4/1.1, 5d04h ago
> > Routing Descriptor Blocks:
> > * 202.97.9.17, from 202.97.9.17, via POS2/0
> > Route metric is 5, traffic share count is 1
> > 202.97.9.161, from 202.97.9.161, via POS2/3
> > Route metric is 5, traffic share count is 1
> > 202.97.10.173, from 202.97.10.173, via ATM4/1.1
> > Route metric is 5, traffic share count is 1
> >
> > The "*" sign indicate the current route used. But normally the traffic
> load
> > will evenly
> > shared in all the parallel paths, no matter how different BW they are.
> Then
> > I wonder if
> > there is any method to adjust the "traffic share count" of the different
> > output interface,
> > so that I can get an uneven load share?
> >
> > The possibility of this idea comes to me when I dig some document on cisco
> > MPLS-TE, it says
> > that if two MPLS tunnels have different BW, the "traffic share count" will
> > be adjusted according
> > to the bandwidth ratio automatically. Because the load share is based on
> the
> > CEF, and is generic
> > to all kinds of IGP, then I think it maybe possible in ISIS.
> >
> > Our environment is: GSR with dCEF enable, IOS 12.0 train. IGP=ISIS.
> >
> > Any input? Thanks!
> >
> >
> > Yu Ning
> > -------------------------------------------
> > (Mr.) Yu(2) Ning(2)
> > ChinaNet Backbone Operation
> > Networking Dep.,Datacom Bureau
> > China Telecom.,Beijing,P.R.C
> > +86-10-66418105/66418121/66418122
> > -------------------------------------------
> >
> >
>
>



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