EIGRP Named Mode Configuration


(Lazaros Agapides) #21

Hello Vinod

The main differences between named and classic modes are the way in which they are implemented (globally for named while both globally and in interface mode for classic) as well as the addition of a sixth K value for the metric.

On the back end, that is, concerning the way that the routers interpret and operate in EIGRP, very little has changed. So a named mode EIGRP router can communicate with a classic EIGRP router. Since you configure the AS number under the EIGRP name configuration, if the AS is the same, they will communicate.

Now the only restriction is the issue with the K values. In order for EIGRP named and classic to interoperate, the number of K values must be the same. There are two possibilities.

One is that the classic EIGRP is being run on an older version of IOS which supports 5 K values. Named EIGRP configured router that receives EIGRP packets with 5 K values will revert to functioning with 5 K values and will not advertise the sixth.

The other possibility is that classic EIGRP is configured on a newer IOS version will actually advertise a sixth K value, but will not have it participate in the metric calculation. This is why you may see a K6 value in a wireshark capture of an EIGRP exchange. This will allow classic EIGRP to successfully interface with a named EIGRP configured router, without actually using that 6th K value for the metric.

I hope this has been helpful!

Laz


(Network E) #22

Hello,
I tested EIGRP named mode in GNS3 with both Dynamips and IOSv. It seems in named mode metric calculation varies from the classic mode. Even the metric calculation in the topology table is not the one in the routing table. Does anyone know the reason please? Thank you.

L0: 10.1.1.1 --R1—192.168.12.0—R2

R1#sho int l0 | inc DLY
  MTU 1514 bytes, BW 8000000 Kbit/sec, DLY 5000 usec,

R2#sho int g0/0 | inc DLY
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

R2#sho ip route 10.1.1.0
Routing entry for 10.1.1.0/24
  Known via "eigrp 100", distance 90, metric 10880, type internal
  Redistributing via eigrp 100
  Last update from 192.168.12.1 on GigabitEthernet0/0, 00:04:48 ago
  Routing Descriptor Blocks:
  * 192.168.12.1, from 192.168.12.1, 00:04:48 ago, via GigabitEthernet0/0
      Route metric is 10880, traffic share count is 1
      Total delay is 12 microseconds, minimum bandwidth is 1000000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1

(Lazaros Agapides) #23

Hello Network

EIGRP named mode supports what is known as the Wide Metrics feature. This feature supports 64-bit metric calculations as opposed to EIGRP classic mode that use 32-bit calculations. This results in varying metric values between the two.

Wide metrics was introduced in order to accommodate high-bandwidth interfaces and Ethernet channels. The increase in available speeds has resulted in incorrect or inconsistent routing behavior with the classic EIGRP routing metrics. The lowest delay that can be configured for an interface is 10 microseconds. As a result, interfaces with speeds of 10 Gbps or more including channeld interfaces will appear to EIGRP as a single GE interface. For this reason, the 64 bit metric calculation has been introduced resulting in different metric values. More on this can be found here:

The new 64 bit metric calculations are designed to be backward compatible with classic EIGRP. However, sometimes scaling can be an issue. More on this can be found below.

I hope this has been helpful!

Laz


(Dominique R) #24

Hi Rene and staff

i just look at EIGRP named to configure a lab in another lesson
So i explore the commands of the configuration modes; in the labs i did, i only used the topology mode base
Image16
I tried to test (just for fun) the command with EIGRP that i suppose to set Multi-Topology Routing
Image18

As you see, IOS answer “VIDEO does not exist”
Could you give me some explanation where i can set a topology that is not the topology base ?
Thanks


(Lazaros Agapides) #25

Hello Dominique

In order to specify a topology other than base, you must define it first. As the following Cisco documentation states:

The topology must be defined globally with the global-address-family command in global address-family configuration mode before the topology can be configured under the EIGRP process.

Now how do you do that? Well, here’s an example:

 Router(config)# global-address-family ipv4 
 Router(config-af)# topology VIDEO
 Router(config-af-topology)# all-interfaces 
 Router(config-af-topology)# end 

You can find out more about this command here:

https://www.cisco.com/c/en/us/td/docs/ios/mtr/command/reference/mtr_book/mtr_01.html#wp1065797

I hope this has been helpful!

Laz


(Dominique R) #26

thank you very much Laz,

After setting topology VIDEO under global-address-family, i went (just) a little further to explore the commands of the cisco doc example


This is what i got

Surprisingly i did not get the network command under ‘config-router-af-topology’

I used this version of IOS in a GNS3 lab

So, and sorry about that, that takes me to a new question: in my example, how to activate the interfaces of the topology VIDEO for EIGRP ?
Thanks


(Lazaros Agapides) #27

Hello Dominique

The example provided from the link I sent you that you attempted is found in the Cisco IOS IP Routing: EIGRP Command Reference document. This is a general overview document providing commands that are common to multiple platforms and IOS versions. Because various IOS versions may deal with commands differently, there is always the possibility that some differences may appear in such documents.

Viewing documents that are more specific to the topics in question, we can get a more accurate view of the commands and how they function. This is the case for this situation. If you look at the following link from Cisco’s “Multitopology Routing Configuration Guide, Cisco IOS Release 15S” document, you will find that the commands are slightly different.

Here you are told to configure the network command outside of the VOICE topology configuration mode. But, you can specify which topology is being used on a per interface basis as shown in the link below:

Try experimenting with these variations in the commands and I believe that you will find the solution that matches your IOS version.

I hope this has been helpful!

Laz