Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

How do I make bandwidth changes effect EIGRP route metrics?

I have two 6509s with several 5505s connected to both of them via GIG links. I also have a two-gig etherchannel between the two 6509s which I want to be used as the best bath between the two. However when I do a show IP route to some remote subnet the path never goes through the etherchannel, but it does through several of the 5505s.

I changed the bandwidth statement on vlan 110 which points to the etherchannel to 2000000 and did a 'clear ip eigrp nei' but the route metrics didn't change. Here are some displays:

ROC-RT6509A-CR#sh ip route 164.72.1.1

Routing entry for 164.72.1.0/25

Known via "eigrp 1", distance 90, metric 2179072, type internal

Redistributing via eigrp 1

Last update from 164.72.43.130 on Vlan255, 00:10:32 ago

Routing Descriptor Blocks:

* 164.72.227.131, from 164.72.227.131, 00:10:32 ago, via Vlan375

Route metric is 2179072, traffic share count is 1

Total delay is 20020 microseconds, minimum bandwidth is 1536 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

164.72.86.3, from 164.72.86.3, 00:10:32 ago, via Vlan270

Route metric is 2179072, traffic share count is 1

Total delay is 20020 microseconds, minimum bandwidth is 1536 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

164.72.2.2, from 164.72.2.2, 00:10:32 ago, via Vlan235

Route metric is 2179072, traffic share count is 1

Total delay is 20020 microseconds, minimum bandwidth is 1536 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

164.72.43.130, from 164.72.43.130, 00:10:32 ago, via Vlan255

Route metric is 2179072, traffic share count is 1

Total delay is 20020 microseconds, minimum bandwidth is 1536 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 2

Vlans 155, 375, 270, 235 are all gig connects between the two 6509s with a bandwidth of 1000000

ROC-RT6509A-CR#sh int vlan 375

lan375 is up, line protocol is up

Hardware is Cat6k RP Virtual Ethernet, address is 00d0.d337.a548 (bia 00d0.d337.a548)

Internet address is 164.72.227.130/25

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

ROC-RT6509A-CR#sh int vlan 110

Vlan110 is up, line protocol is up

Hardware is Cat6k RP Virtual Ethernet, address is 00d0.d337.a548 (bia 00d0.d337.a548)

Description: Etherchannel between 6509 A & B

Internet address is 164.72.123.2/25

MTU 1500 bytes, BW 2000000 Kbit, DLY 10 usec,

Vlan 110 is the two-gig etherchannel between the two 6509s with a bandwidth of 2000000

IP-EIGRP topology entry for 164.72.1.0/25

State is Passive, Query origin flag is 1, 4 Successor(s), FD is 2179072

Routing Descriptor Blocks:

!

164.72.227.131 (Vlan375), from 164.72.227.131, Send flag is 0x0

Composite metric is (2179072/2178816), Route is Internal

Vector metric:

Minimum bandwidth is 1536 Kbit

Total delay is 20020 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

!

!

164.72.123.1 (Vlan110), from 164.72.123.1, Send flag is 0x0

Composite metric is (2179072/2178816), Route is Internal

Vector metric:

Minimum bandwidth is 1536 Kbit

Total delay is 20020 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

!

!

As can be seen with the 'show ip eigrp top 164.72.1.0 255.255.255.128' the composite metric of both vlan 375 and 110 are exactly the same even though the bandwidth of 110 is twice as large.

Vlan 110 should be the best route between the two 6509s to subnet 164.72.1.0, but it doesn't even show up in the route list as show above.

I was told to do a 'clear ip eigrp topology' to get the bandwidth change to be computed, but that command isn't available in the 6509 IOS which is 12.1(8a)E5.

1. How do I get vlan 110 to be the best route?

2. Do I need a late IOS to get the 'clear ip eigrp topology' command?

8 REPLIES
Anonymous
N/A

Re: How do I make bandwidth changes effect EIGRP route metrics?

Changing the bandwidth on the 2Gig link won't make this link the best path. E-IGRP uses the MINIMUM bandwidth along the path to the destination plus the sum of the delays on each link along the path to calculate the metric (scaled in various ways).

Your minimum bandwidth on both paths is 1536, and the sum of the delays on both paths are 20020.

(10^7/min bw + (sum of delay)/10) * 256 , = (6510 + 2002) * 256 = 2179072 (your metrics on both paths)

Your two paths are equal, and will remain equal even if you change the bandwidth on the 2G link.

If you change the delay on the 2G link (lower it), the sum of the delays will be lower for this path.

e-igrp will load balance up to 4 equal cost paths, by default. You have 4 paths in your routing table. perhaps the 2G link is the unlucky 5th path.

clear ip eigrp nei should reset the neighbors' state, and thus clear the topology table, also causing a disruption to your network, by the way.

New Member

Re: How do I make bandwidth changes effect EIGRP route metrics?

This is great information - thank you.

So I should go ahead and configure a lower delay metric on the 2GIG etherchannel vlan and that should cause that link to be the best path?

Gold

Re: How do I make bandwidth changes effect EIGRP route metrics?

You're always better off using the delay to make one path better than an other path, rather than the bandwith, so I'd increase the delay on th 2gig ethernerchannel. Clear ip eigrp topo was added with CSCdk60230, which should be back in the 12.0(2)T range, but it might not have been pulled into the E train 'til later. What version is the CAT actually running?

Russ.W

New Member

Re: How do I make bandwidth changes effect EIGRP route metrics?

The Cat6500 OS is 12.1(8a)E5.

How does increasing the delay on the 2 gig etherchannel make that a better path? I would think I should decrease the delay - make the delay less. Am I thinking backwards on this? - thanks

New Member

Re: How do I make bandwidth changes effect EIGRP route metrics?

Sorry - the Cat MSFC IOS - not the Cat OS - is 12.1(8a)E5.

Gold

Re: How do I make bandwidth changes effect EIGRP route metrics?

Yes, you should decrease the delay. I thought you were trying to not prefer the 2gig path.

clear ip eigrp topo was integrated in 12.0 in the mainline IOS versions, and should be in all 12.1 images. I'm not certain where it was picked up on the E train.

Russ.W

New Member

Re: How do I make bandwidth changes effect EIGRP route metrics?

Thanks Russ -

One last question about the delay. So for sure I want to increase the delay on the 2 gig etherchannel vlan and not decrese it?

New Member

Re: How do I make bandwidth changes effect EIGRP route metrics?

Disregard the last question - I saw your answer. Thanks for you help.

227
Views
5
Helpful
8
Replies