Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


EIGRP Multicast vs Unicast

Posted on 2016-11-05
Medium Priority
Last Modified: 2016-11-12
If I understand EIGRP Unicast , Routers are configured with Neighbor command and they send queries to whatever router they are configured as neighbor with.

with Multicast, there is no Neighbor command, and routers send their queries to a Multicast adresss
Now does that mean each router own that Multicast address of ?

example if  router RouterA is connected to RouterB, then which router own the ?

Thank you
Question by:jskfan
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
LVL 31

Accepted Solution

Predrag earned 2000 total points
ID: 41875581
You are mixing apples and oranges.

Multicast address is address for all EIGRP routers.
It is like radio transmission.
Let's say you set radio receiver on 100.5Mhz - if there is no one broadcasting, sure you will not hear anything. When someone start to broadcast on 100.5Mhz frequency you will hear it.
In case of EIGRP source traffic is unicast address (radio station-1 with address and destination is all EIGRP routers (frequency Every router that is configured to listen on will hear message and if necessary answer. But answer from multicast IP address would not make much sense - it would be unclear who answered on message? So answers are unicast packets.

Here is a proof (wireshark capture of EIGRP traffic) - no one is ever sending from - every router is just receiving on that address (all EIGRP routers are tuned to listen on that frequency).
 Proof is in the pudding
No one own, EIGRP routers are just listening to transmissions there.
When EIGRP neighbors are configured with neighbor command all messages are sent as unicast traffic directly to configured neighbor (that's why all neighbors on specific segment must be configured manually).

Author Comment

ID: 41876099
Radio frequency is somewhere in the AIR.
Router Multicast ip address, it is kind of virtual ip address that might be added to each router when the routes are advertised.
In other words where is the physical location of Multicast address ?
LVL 31

Expert Comment

ID: 41876173
In the air. It is not configured on any device.
Moving data to the cloud? Find out if you’re ready

Before moving to the cloud, it is important to carefully define your db needs, plan for the migration & understand prod. environment. This wp explains how to define what you need from a cloud provider, plan for the migration & what putting a cloud solution into practice entails.


Author Comment

ID: 41877617
I am not saying configured.
but when you enable EIGRP on the router, the system will add the Ip address . somewhere.
I know we do not care too much where physically is, but just curious.
LVL 31

Expert Comment

ID: 41877788
I quit.

Author Comment

ID: 41878083
Keep off my Questions, please

Author Closing Comment

ID: 41884700

Featured Post

Survive A High-Traffic Event with Percona

Your application or website rely on your database to deliver information about products and services to your customers. You can’t afford to have your database lose performance, lose availability or become unresponsive – even for just a few minutes.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Understanding FTPS File transfer is a common requirement in most Enterprises. While there are numerous ways to get a file from Point A to Point B over a network, perhaps the most common method still in use is FTP – File Transfer Protocol. FTP is …
There are two basic ways to configure a static route for Cisco IOS devices. I've written this article to highlight a case study comparing the configuration of a static route using the next-hop IP and the configuration of a static route using an outg…
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

688 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question