I think this was the exact issue that I was running into. Given this
information, it seems that this decreases the usefulness of the variance
command greatly. I'll try to draw the my scenario in text:
[A]
/ \
/ \
[B] [C]
\ /
\ /
[D]
|
|
[E]
Let's start out with a metric of 10 on each link. At Router A, it sees
two paths to network E, each with a metric of 30. Now let's make set
the C-D metric to 20. Router A will now pick the path through B because
of the lower metric (30). Since the advertised distance from C is also
30--not greater than the FD--then it becomes a feasible successor. In
this case, addind the variance command would have an effect.
Now, make the C-D metric 30. Router A will install the route through B
with a metric of 30. However, since the advertised distance from C (40)
is now greater than the FD, router C will not be entered into the EIGRP
topology table as a feasible successor. In this situation, variance
would have no relevance because we only have a single feasible successor
in the table.
Is that basically it?
Thanks!
John
>>> Jim Brown 1/31/02 8:24:00 AM >>>
Even with the variance command a neighbor might not be considered a
feasible
successor. Remember a feasible successor is a path whose reported
distance
is less than the feasible distance.
This is a loop prevention method in EIGRP.
Read the section, "Deciding if a Path is Loop-Free" in the document at
the
link below
http://www.cisco.com/warp/public/103/eigrp1.html#6
I guarantee a light bulb will come on above your head after you read
this.
-----Original Message-----
From: John Neiberger [mailto:[EMAIL PROTECTED]]
Sent: Thursday, January 31, 2002 7:57 AM
To: [EMAIL PROTECTED]
Subject: Re: Variance for Eigrp...does it actually work?? [7:33835]
I don't really have an answer, this is more of a "me too" email. I've
only
bothered with variance once in a practice lab and I was not able to
make it
work even after setting the variance to a ridiculously high number.
No
matter what I did, I was not able to get both EIGRP routes into the
routing
table.
At some point I need to go back and figure out why it wasn't working
but
I've been avoiding it.
John
>>> "Cisco Nuts" 1/31/02 12:05:03 AM >>>
Hello,I am testing out the variance command under eigrp and it does not
seem
to be working the way it is explained in the CCNP routing guide by
CiscoPress. Any ideas ? Sorry, Long post but need help.I have RTA
connected
to RTB and RTC via FR physical intf. running eigrp 1RTB and RTC are
connected to BBR via serials also running eigrp 1BBR is connected to TS
via
serial running eigrp 1 and igrp 1TS is connected to REMOTE running
rip.RTA
to RTB to BBR have bandwidth = 64 configed.RTA to RTC to BBR have the
default bw = 1.544On RTA, the route to Rip netw. 12. and 13. on Remote
show
up via the RTC to BBR to TS to Remote route....which is correct.D EX
12.0.0.0/8 [170/3245056] via 192.168.10.243, 00:12:37, Serial0 D EX
13.0.0.0/8 [170/3245056] via 192.168.10.243, 00:13:42, Serial0 The
metric
via RTB to BBR to TS to Remote is 41538560 as inD EX 12.0.0.0/8
[170/41538560] via 192.168.10.242, 00:00:17, Serial0 D EX 13.0.0.0/8
[170/41538560] via 192.168.10.242, 00:00:17, Serial0 After doing the
math,(
multiplied 3245056 x 13 to get 42185728 which is greater than
41538560), I
configed a variance of 13 on RTA and expected to see 2 routes to
networks
12. and 13. but only 1 route shows up, that thru RTC.Is there a reason
why?Thank you. :
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