From: Brent D. Stewart (brent@stewart.hickory.nc.us)
Date: Wed May 28 2003 - 20:14:26 GMT-3
Actually, by default delay is a standard value arbitrarily associated
with the network type and is not dynamically measured or changed. So
hops have no affect on it, nor does cable length.
Brent
-----Original Message-----
From: Danny.Andaluz@triaton-na.com [mailto:Danny.Andaluz@triaton-na.com]
Sent: Wednesday, May 28, 2003 7:11 PM
To: tschaffran@cconlinelabs.com; Brent D. Stewart;
ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
I said "indirectly".
-----Original Message-----
From: Tony Schaffran [mailto:tschaffran@cconlinelabs.com]
Sent: Wednesday, May 28, 2003 7:07 PM
To: Andaluz, Danilo, Triaton/NA; brent@stewart.hickory.nc.us;
ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
You mentioned hop count affecting delay. The router does not care about
that either in reference to EIGRP. I just threw that out there.
Tony Schaffran
Network Analyst
CCIE #11071
CCNP, CCNA, CCDA
NNCDS, NNCSS, CNE, MCSE
www.cconlinelabs.com
Your #1 choice for online cisco rack rentals.
-----Original Message-----
From: Danny.Andaluz@triaton-na.com [mailto:Danny.Andaluz@triaton-na.com]
Sent: Wednesday, May 28, 2003 3:55 PM
To: tschaffran@cconlinelabs.com; brent@stewart.hickory.nc.us;
ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
Physically, delay is affected by cable length, but I don't think the
router cares about that. I think the delay is what it is configured to
be. If I'm wrong someone please correct me.
-----Original Message-----
From: Tony Schaffran [mailto:tschaffran@cconlinelabs.com]
Sent: Wednesday, May 28, 2003 6:41 PM
To: Andaluz, Danilo, Triaton/NA; brent@stewart.hickory.nc.us;
ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
If you want to get that deep into it, cablelength also contributes to
delay. Maybe they should have a K value for that too.
:)
Tony Schaffran
Network Analyst
CCIE #11071
CCNP, CCNA, CCDA
NNCDS, NNCSS, CNE, MCSE
http://www.cconlinelabs.com/
Your #1 choice for online cisco rack rentals.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Danny.Andaluz@triaton-na.com
Sent: Wednesday, May 28, 2003 2:14 PM
To: brent@stewart.hickory.nc.us; ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
I'll tell you what. Looking into it a little deeper, I found that hop
counts do have an direct affect on delay. The higher the hop count, the
higher the delay. So, while hop counts are not directly used to
calculate the metric, they indirectly are.
Danny
-----Original Message-----
From: Brent D. Stewart [mailto:brent@stewart.hickory.nc.us]
Sent: Wednesday, May 28, 2003 4:37 PM
To: Andaluz, Danilo, Triaton/NA; ccielab@groupstudy.com
Subject: RE: EIGRP metric (just to be sure)
No. For an excellent discussion of this, refer to Alvaro Retana's book
"EIGRP for IP".
EIGRP builds a metric using the equation:
Metric= (k1*bw + k2*bw/(256-load) + k3*delay) (k5/(reliability+k4)
By default, k1=1, k2=0, k3=1, k4=0, k5=0 and k2, k4, and k5 really
shouldn't ever be changed. K1 and k3 are very seldom changed. If k5=0,
the last part is ignored, so this reduces to:
Metric= bw + delay
Each of these deserves a discussion.
"bw" is actually 10^7/min(bw). In other words, the bw part uses the
slowest link along the path and is inversely proportional to 1 million.
"delay" is an accumulation of all interface delays along the path.
Load and reliability should not be included in the calculation (by
changing k values) because EIGRP does not send out updates if they
change. MTU isn't even an option, but the idea was that it might be
used for minimum MTU discovery along a path. As far as I know, this was
never implemented.
EIGRP actually also tracks hops. The default max is 100. EIGRP doesn't
use this in the metric, it's there as a loop-detection mechanism.
Regards,
Brent D. Stewart
-----Original Message-----
From: Danny.Andaluz@triaton-na.com [mailto:Danny.Andaluz@triaton-na.com]
Sent: Wednesday, May 28, 2003 2:41 PM
To: ccielab@groupstudy.com
Subject: EIGRP metric (just to be sure)
Hello, Group. Is the below correct with regards to how eigrp picks a
best route? Does it do it like the below or does each value get taken
into account for the composite metric?
BW
Delay (in case of tie with BW) ?
relia (in case of tie with delay) ?
load (in case of tie with relia) ?
MTU (in case of tie with load) ?
Thanks,
Danny
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