# bgp weight calculation

Discussion in 'Cisco' started by Glenn, Oct 28, 2003.

1. ### GlennGuest

Here is a quicky ..

I have 2 neighbors, and I want to change to weights on each one to have
a bit more control on outbound traffic. The default weight is 32,768,
and can be a number 1 - 65,535 ..

What would be a good way to calculate what weight I want on each one when
say I want around 65% going out one neighbor and 35% going out the other?

------------------------------------- -- - -
glenn
http://www.dallaslamers.org

"Even if you do learn to speak correct English,
whom are you going to speak it to?"

#define WHO 1

int main(void)
{
printf("%d r0x0rs!!!\n", WHO);
}

Glenn, Oct 28, 2003

2. ### Barry MargolinGuest

In article <>,
Glenn <> wrote:
>Here is a quicky ..
>
>I have 2 neighbors, and I want to change to weights on each one to have
>a bit more control on outbound traffic. The default weight is 32,768,
>and can be a number 1 - 65,535 ..
>
>What would be a good way to calculate what weight I want on each one when
>say I want around 65% going out one neighbor and 35% going out the other?

It always uses the route with the higher weight, it's not proportional.

The only way to get proportional load sharing with BGP is to partition the
routes you learn based on how much traffic goes to each prefix, and then
make one path preferred for the prefixes with 65% of the traffic and the
other path preferred for the remainder. This is likely to be *very*
difficult.

--
Barry Margolin,
Level(3), Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

Barry Margolin, Oct 28, 2003

3. ### Jesper SkriverGuest

On 28 Oct 2003 17:20:57 -0500, Glenn wrote:
> Here is a quicky ..
>
> I have 2 neighbors, and I want to change to weights on each one to have
> a bit more control on outbound traffic. The default weight is 32,768,
> and can be a number 1 - 65,535 ..
>
> What would be a good way to calculate what weight I want on each one when
> say I want around 65% going out one neighbor and 35% going out the other?

Chainging weights are in 99% of the cases *NOT* what you want to do, as
it's local to that router, if you have other routers running BGP, or if
you ever will, local preference is what you want to change - but both
weight and local pref is like a sledge hammer, often you only want to
influence the path decisition, so often one use AS path prepending.

/Jesper

--
Jesper Skriver, CCIE #5456, FreeBSD committer

Jesper Skriver, Oct 28, 2003
4. ### GlennGuest

> The only way to get proportional load sharing with BGP is to partition the
> routes you learn based on how much traffic goes to each prefix, and then
> make one path preferred for the prefixes with 65% of the traffic and the
> other path preferred for the remainder. This is likely to be *very*
> difficult.

Is there another method you could recomend?

------------------------------------- -- - -
glenn
http://www.dallaslamers.org

"Even if you do learn to speak correct English,
whom are you going to speak it to?"

#define WHO 1

int main(void)
{
printf("%d r0x0rs!!!\n", WHO);
}

Glenn, Oct 28, 2003
5. ### Kevin SuGuest

Cisco introduces a new feature called BGP link-bandwidth with which
you can do uneaqual cost load sharing. Take the following commands for
reference:
1. enable

2. configure {terminal | memory | network}

3. router bgp [as-number]

Glenn <> wrote in message news:<>...
> > The only way to get proportional load sharing with BGP is to partition the
> > routes you learn based on how much traffic goes to each prefix, and then
> > make one path preferred for the prefixes with 65% of the traffic and the
> > other path preferred for the remainder. This is likely to be *very*
> > difficult.

>
> Is there another method you could recomend?
>
> ------------------------------------- -- - -
> glenn
> http://www.dallaslamers.org
>
> "Even if you do learn to speak correct English,
> whom are you going to speak it to?"
>
> #define WHO 1
>
> int main(void)
> {
> printf("%d r0x0rs!!!\n", WHO);
> }

Kevin Su, Oct 29, 2003