load balancing with a failover
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From: yo on 3 Mar 2006 11:20 ok, im not sure if this is possible but if it is im sure someone here knows how to get this working. i have a router with 3 t1 links. im doing per packet load balancing on the 1st 2 with the 3rd one being in admin down state and i only bring it up when they need additional bandwidth. i want to conver this 3rd line into a fail over link, so that when one of the 2 active load balancing lines goes down, the 3rd line will do load balancing with the line that did not go down. is this possible and how can i go about it. fyi im using eigrp routing and per packet loading. Thanks P
From: Charlie Root on 3 Mar 2006 16:09 <yo> wrote in message news:70rg02td6bo3p6n7b7sd71aifkaelbj21h(a)4ax.com... > ok, im not sure if this is possible but if it is im sure someone here > knows how to get this working. > > > i have a router with 3 t1 links. im doing per packet load balancing on > the 1st 2 with the 3rd one being in admin down state and i only bring > it up when they need additional bandwidth. > > i want to conver this 3rd line into a fail over link, so that when one > of the 2 active load balancing lines goes down, the 3rd line will do > load balancing with the line that did not go down. > you could use 'backup interface <name_of_backup_interface>' command in primary interface configuration. Here is what happens: CE-2.LAB(config)#in se 0/0:0 CE-2.LAB(config-if)#backup interface atm0/1 *Sep 6 13:24:43.174: %LINK-5-CHANGED: Interface ATM0/1, changed state to standby mode Unfortunately this is 1:1 redundancy, i.e. you can't specify the same backup interface for two primary interfaces. However, if all of your three lines are of the same bandwidth and connected to the same routers, why don't you just bundle them into multi-link PPP or do per-packet load-balancing across all three lines? Kind regards, iLya
From: yo on 3 Mar 2006 16:39 its a cost thing they dont want to load balance the 3rd line and only want it as a backup solution. On Fri, 3 Mar 2006 22:09:17 +0100, "Charlie Root" <root(a)localhost.example.com> wrote: ><yo> wrote in message news:70rg02td6bo3p6n7b7sd71aifkaelbj21h(a)4ax.com... >> ok, im not sure if this is possible but if it is im sure someone here >> knows how to get this working. >> >> >> i have a router with 3 t1 links. im doing per packet load balancing on >> the 1st 2 with the 3rd one being in admin down state and i only bring >> it up when they need additional bandwidth. >> >> i want to conver this 3rd line into a fail over link, so that when one >> of the 2 active load balancing lines goes down, the 3rd line will do >> load balancing with the line that did not go down. >> > >you could use 'backup interface <name_of_backup_interface>' command in >primary interface configuration. Here is what happens: > >CE-2.LAB(config)#in se 0/0:0 >CE-2.LAB(config-if)#backup interface atm0/1 >*Sep 6 13:24:43.174: %LINK-5-CHANGED: Interface ATM0/1, changed state to >standby mode > >Unfortunately this is 1:1 redundancy, i.e. you can't specify the same backup >interface for two primary interfaces. However, if all of your three lines >are of the same bandwidth and connected to the same routers, why don't you >just bundle them into multi-link PPP or do per-packet load-balancing across >all three lines? > >Kind regards, >iLya >
From: Charlie Root on 3 Mar 2006 18:15 <yo> wrote in message news:9rdh02drpjnvq7j0m4l63hgcoafkif1rov(a)4ax.com... > > its a cost thing they dont want to load balance the 3rd line and only > want it as a backup solution. > ok, then the only solution I see is to use GRE tunnel between loopbacks of two routers, run EIGRP _only_ over the tunnel and have RTR tracker to setup route to the remote loopback over thirds interface only if one of the two "primary" links goes down. There will be slight overhead of GRE encapsulation and your routers CPU will be penalized, but at the moment I can't think of any alternative. I'm sorry, gotta go now. If you don't solve this issue during the weekend, I'll post configs with GRE on monday. Kind regards, iLya > > > On Fri, 3 Mar 2006 22:09:17 +0100, "Charlie Root" > <root(a)localhost.example.com> wrote: > >><yo> wrote in message news:70rg02td6bo3p6n7b7sd71aifkaelbj21h(a)4ax.com... >>> ok, im not sure if this is possible but if it is im sure someone here >>> knows how to get this working. >>> >>> >>> i have a router with 3 t1 links. im doing per packet load balancing on >>> the 1st 2 with the 3rd one being in admin down state and i only bring >>> it up when they need additional bandwidth. >>> >>> i want to conver this 3rd line into a fail over link, so that when one >>> of the 2 active load balancing lines goes down, the 3rd line will do >>> load balancing with the line that did not go down. >>> >> >>you could use 'backup interface <name_of_backup_interface>' command in >>primary interface configuration. Here is what happens: >> >>CE-2.LAB(config)#in se 0/0:0 >>CE-2.LAB(config-if)#backup interface atm0/1 >>*Sep 6 13:24:43.174: %LINK-5-CHANGED: Interface ATM0/1, changed state to >>standby mode >> >>Unfortunately this is 1:1 redundancy, i.e. you can't specify the same >>backup >>interface for two primary interfaces. However, if all of your three lines >>are of the same bandwidth and connected to the same routers, why don't you >>just bundle them into multi-link PPP or do per-packet load-balancing >>across >>all three lines? >> >>Kind regards, >>iLya >> >
From: Charlie Root on 3 Mar 2006 18:27
<ciscodagama(a)gmail.com> wrote in message news:1141426197.243387.39680(a)p10g2000cwp.googlegroups.com... > Charlie Root wrote: > >> Unfortunately this is 1:1 redundancy, i.e. you can't specify the same >> backup >> interface for two primary interfaces. However, if all of your three lines >> are of the same bandwidth and connected to the same routers, why don't >> you >> just bundle them into multi-link PPP or do per-packet load-balancing >> across >> all three lines? > > One semi-workaround to this problem with using one interface to backup > two other interface might be to use the "backup load" command in > addition to specifying the backup interface for one of the interfaces. > That way, if the interface in the pair not being backed up went down, > it would cause an increase in the load of the interface that does have > a backup (but which is still up) and thus result in the the backup > interface to come up for load reasons rather than for link failure if > the threshold is set correctly. > C-d-G, this is neat workaround. I didn't notice that now there is 'load' option now (used backup really long ago). If you don't mind I'd add some bits to your proposal - instead of backing up individual interface, get them into MLP bundle (only two links) and then backup will be for the whole bundle. I just tried - the backup command can be applied to Multilink interface, but I can't test until monday if it actually going to work. Though still as you've said choosing threshold values will require good quality crystal ball. Kind regards, iLya |