[c-nsp] Unintentional load balancing of traffic

[Daniel Dib]

-----Original Message-----
From: CiscoNSP List [mailto:CiscoNSP_list at hotmail.com] 
Sent: den 18 september 2015 08:27
To: Daniel Dib; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Unintentional load balancing of traffic

Thanks Daniel.

> Please give us a show ip route x.x.x.x and show ip ospf data x.x.x.x 
> so that

> we can analyse the routing.


#sh ip route xxx.xxx.xxx.218

Routing entry for xxx.xxx.xxx.218/32

  Known via "ospf 100", distance 110, metric 205, type intra area

  Last update from yyy.yyy.yyy.204 on Port-channel1.17, 18:09:01 ago

  Routing Descriptor Blocks:

  * yyy.yyy.yyy.208, from xxx.xxx.xxx.218, 1w2d ago, via Port-channel1.26

      Route metric is 205, traffic share count is 1

    yyy.yyy.yyy.204, from xxx.xxx.xxx.218, 18:09:01 ago, via
Port-channel1.17

      Route metric is 205, traffic share count is 1


Dont have that command "show ip ospf data x.x.x.x"  (precisely) on this
router:


#show ip ospf data ?                       

  adv-router        Advertising Router link states

  asbr-summary      ASBR summary link states

  database-summary  Summary of database

  external          External link states

  network           Network link states

  nssa-external     NSSA External link states

  opaque-area       Opaque Area link states

  opaque-as         Opaque AS link states

  opaque-link       Opaque Link-Local link states

  router            Router link states

  self-originate    Self-originated link states

  summary           Network summary link states

  |                 Output modifiers

  <cr>


> How is your OSPF setup? Is each POP in its own area or are you running 
> everything in area 0?


Single area, alll in area 0


Cheers.

---------------------------------------------------------------

What is your auto-cost reference-bandwidth set to? 
Show ip ospf | i Reference

How many routers are between this one and the router where the route is? Do
you have Gigabit or 10 Gigabit links?
It looks like you have 3 or 4 routers between this one and the other router
and the link cost of those is set to 1.

Since this is all in one area we would have to analyse the router LSAs to
compute the metric. The router LSA is referenced by the Router ID (RID) so
we would have to do:

Show ip ospf data router <RID_OF_LOCAL_ROUTER>
Show ip ospf data router <RID_OF_INTERMEDIARY_ROUTER>
Show ip ospf data router <RID_OF_EXIT_ROUTER>

Could you provide a brief ASCII or URL to a topology?

The metric is computed to 205 across both paths so it's natural for it to do
ECMP but now we just need to find out why.

Regards,
Daniel