[c-nsp] OSPF equal cost load balancing

[CBL]

What if you were to setup four BDIs running OSPF/MPLS across these two
physical interfaces. Two BDIs per physical interface. Would that make ECMP
work correctly using an ASR920?

We're going to be in the same boat soon too.. ASR920's on both sides with
OSPF across two physical paths and worried about load sharing. Most of our
traffic is MPLS xconnects traversing these links (licensed backhauls).


On Wed, Aug 30, 2017 at 6:35 PM, CiscoNSP List <CiscoNSP_list at hotmail.com>
wrote:

> AAh - Thank you James!  So the ASR920 will not ECMP over 2 links, it
> requires 4...that would explain the difference between egress/ingress (and
> why the 920 is not working particularly well!)
>
>
> Yes, this is ECMP, not LAG - So changing the load sharing algorithm can
> only be done globally (As I tried to do it under the individual interfaces,
> and was only presented with per dst as an option)
>
>
> (config-if)#ip load-sharing ?
>   per-destination  Deterministic distribution
>
>
> So, changing globally will potentially cause a service disruption? (May
> need to do this in maintenance window) - Do you suggest "include-ports" as
> a possible candidate?
>
>
> #ip cef load-sharing algorithm ?
>   include-ports  Algorithm that includes layer 4 ports
>   original       Original algorithm
>   tunnel         Algorithm for use in tunnel only environments
>   universal      Algorithm for use in most environments
>
> And yes, we are running MPLS over these links (But not a LAG as mentioned)
> - So does your comment re MPLS hasting still apply to our setup, or only to
> a LAG?
>
>
> Thanks again for your response - Extremely helpful!
>
>
> ________________________________
> From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of James
> Bensley <jwbensley at gmail.com>
> Sent: Thursday, 31 August 2017 6:43 AM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] OSPF equal cost load balancing
>
> I think two layer ECMP links are being used here, both of which are in
> the IGP. Are you running MPLS over these links too?
>
> The ME3600 is able to ECMP over any number of links as far as I know
> (up to the max, which is 8 or 16) however I think the ASR920 will only
> ECMP over 4 or 8 links (so not 2 as in your case). This could be the
> problem here.
>
> Could you also try to change the CEF load balancing algorithm
> (assuming this is ECMP and not LAG, this won't affect a LAG):
>
> ASR920(config)#ip cef load-sharing algorithm ?
>   include-ports  Algorithm that includes layer 4 ports
>   original       Original algorithm
>   tunnel         Algorithm for use in tunnel only environments
>   universal      Algorithm for use in most environments
>
> If it is a LAG then on the ASR920 try to adjust these options:
>
> ASR920(config)#port-channel load-balance-hash-algo ?
>   dst-ip                 Destination IP
>   dst-mac                Destination MAC
>   src-dst-ip             Source XOR Destination IP Addr
>   src-dst-mac            Source XOR Destination MAC
>   src-dst-mixed-ip-port  Source XOR Destination Port, IP addr
>   src-ip                 Source IP
>   src-mac                Source MAC
>
> If you're running MPLS over the LAG the ASR920 can hash MPLS over the
> LAG and the ASR920 should hash over 2 links just fine.
>
> Cheers,
> James.
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