Re: 1GE L3 aggregation

[Owen DeLong <owen () delong com>]

> On Jun 22, 2016, at 23:17 , Mark Tinka <mark.tinka () seacom mu> wrote:
>
>
>
> On 23/Jun/16 08:07, Owen DeLong wrote:
>
> > If it’s 100% for redundancy, why not just ECMP defaults and not take a full table?
>
> Well, firstly, ring length may be different on either end. So you can't
> always guarantee ECMP of traffic to/from the device (without much
> difficulty such as MPLS-TE).

Unless the difference is HUGE, you usually don’t really care.

> You also can't do hop-by-hop routing based on 0/0 or ::/0 when the ring
> contains multiple devices also doing the same thing. You'll just create
> a loop. MPLS-based forwarding is your friend here.

Who said anything about a ring. He is advertising a /24 to 2 upstream providers.

Likely these are two separate transit circuits.

> But yes, if your device is not in a ring, then your suggestion is fine.

Even if you’re in a ring if you’ve got two transit providers at some random point on the ring, it still probably 
doesn’t make a meaningful difference between full feeds from each vs. ECMP, because it’s pretty unlikely that the AS 
PATH length is affected by the ring length.

Owen