Hi Joe
Thanks, I'm confused.com it's almost like it bypasses the eigrp topology table
and looks at the all-links when variance is selected and the initial statement
doesn't hold true.
-- BR Tony Sent from my iPhone on 3 > On 7 Oct 2013, at 08:54, Joe Astorino <joeastorino1982_at_gmail.com> wrote: > > Hmmmm....also this Cisco white paper seems to agree with the book and with how I thought it worked. They have a simplified version of what you are testing with easier to read numbers. > > In the example, the path through D is not chosen because it's metric is not < variance * FD. However, it also goes on to make this point: > > "Also, the reported distance of neighbor D is 25, which is greater than the feasible distance (FD) of 20 through C. This means that, even if variance is set to 3, the E-D-A path is not selected for load balancing because Router D is not a feasible successor." > > This seems to certainly be making the case that to be considered for unequal cost load balancing via variance, a path must first pass the feasibility condition. Clearly, your lab results show otherwise though. > > http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d. shtml#var > > > > >> On Mon, Oct 7, 2013 at 3:34 AM, Joe Astorino <joeastorino1982_at_gmail.com> wrote: >> This certainly seems strange to me. Granted, it is like 4AM or something here, but if you had asked me I would have thought EIGRP would not consider the F1/0 path for anything, given it doesn't meet the feasibility condition. I'd certainly be interested to hear if anybody else has an answer. >> >> >> >> >>> On Sun, Oct 6, 2013 at 2:53 PM, Tony Singh <mothafungla_at_gmail.com> wrote: >>> CCNP ROUTE 642-902 Official Certification Guide >>> >>> "Routes that are neither successor nor feasible successor can never be >>> added to the IP routing table, regardless of the variance setting" >>> >>> I did a little lab >>> >>> --- r2 --- >>> r1 ----r3 ---- r5 loopback 5.5.5.5 >>> ----r4 ---- >>> >>> >>> no variance >>> >>> all-links >>> P 5.5.5.5/32, 1 successors, FD is 158720, serno 55 >>> via 10.0.0.1 (158720/156160), FastEthernet0/0 >>> via 20.0.0.1 (161536/158976), FastEthernet1/1 >>> via 30.0.0.1 (1790976/156160), FastEthernet1/0 >>> >>> topology >>> P 5.5.5.5/32, 1 successors, FD is 158720 >>> via 10.0.0.1 (158720/156160), FastEthernet0/0 >>> via 30.0.0.1 (1790976/156160), FastEthernet1/0 >>> >>> global-rib >>> D 5.5.5.5 [90/158720] via 10.0.0.1, 00:00:44, FastEthernet0/0 >>> >>> >>> the reason we choose f1/0 path as FS over f1/1 is due to the AD<FD of >>> successor holding true even if it has a worse FD - expected behaviour and >>> end result no load-balancing as no equal cost paths (max 4 equal cost paths >>> by default) >>> >>> >>> >>> >>> if I apply a variance of x2 >>> >>> >>> >>> all-links >>> P 5.5.5.5/32, 2 successors, FD is 158720, serno 52 >>> via 10.0.0.1 (158720/156160), FastEthernet0/0 >>> via 20.0.0.1 (161536/158976), FastEthernet1/1 >>> via 30.0.0.1 (1790976/156160), FastEthernet1/0 >>> >>> topology >>> P 5.5.5.5/32, 2 successors, FD is 158720 >>> via 10.0.0.1 (158720/156160), FastEthernet0/0 >>> via 30.0.0.1 (1790976/156160), FastEthernet1/0 >>> >>> global-rib >>> D 5.5.5.5 [90/158720] via 10.0.0.1, 00:00:53, FastEthernet0/0 >>> [90/161536] via 20.0.0.1, 00:00:53, FastEthernet1/1 >>> >>> >>> ok so we're now permitting the f1/1 path being installed as a viable >>> load-balancing destination, this shows me two things, first that dual will >>> permit a non-successor or non-feasible successor into global rib as viable >>> load-balancing paths and second dual compares the end-to-end FD for making >>> a decision on which path it would prefer to load-balance looking at the >>> all-links topology as f1/1 has a lower FD than f1/0 >>> >>> >>> >>> this does make the above argument invalid - im wondering if EIGRP has since >>> been enhanced for this DUAL behaviour? if so then I guess the whole point >>> for the statement in the first place was to avoid a loop i.e if you're not >>> a successor or feasible successor then you a loop, what has changed? >>> >>> >>> -- >>> BR >>> >>> Tony >>> >>> >>> Blogs and organic groups at http://www.ccie.net >>> >>> _______________________________________________________________________ >>> Subscription information may be found at: >>> http://www.groupstudy.com/list/CCIELab.html >> >> >> >> -- >> Regards, >> >> Joe Astorino >> CCIE #24347 >> http://astorinonetworks.com >> >> "He not busy being born is busy dying" - Dylan > > > > -- > Regards, > > Joe Astorino > CCIE #24347 > http://astorinonetworks.com > > "He not busy being born is busy dying" - Dylan Blogs and organic groups at http://www.ccie.netReceived on Mon Oct 07 2013 - 15:31:29 ART
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