?
Solved

Understanding Passive interface in EIGRP

Posted on 2013-01-01
12
Medium Priority
?
419 Views
Last Modified: 2013-01-10
I need to give an example in order to understand Passive interface:
Let s say I have a router R2 which is an ABR between OSPF are 0 and area 3 and EIGRP AS 10.
it has S0/1 connecting to area 0 and E0 connecting to area 3 and S0/2 connecting to EIGRP AS 10
now if I configure S0/1 and E0 as passive interfaces , then area 0 and area 3 will not get any routes from EIGRP 10 and the other way around I guess will also be true,EIGRP10 will not get any OSPF routes from area 0 and area 3.

My question is if later, I will try to redistribute OSPF into EIGRP 10 and EIGRP 10 into Area 0 and Area 3,will still be possible even if the afore-mentioned interfaces are configured as passive ?

Thank you
0
Comment
Question by:jskfan
[X]
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
  • 2
  • +2
12 Comments
 

Assisted Solution

by:davidy2001
davidy2001 earned 400 total points
ID: 38735278
it depends on your purpose. Passive interface is one way traffic. Usually redistribution is two way traffic. If you hope it has full function between ERGRP and OSPF, you do not configure that interface as passive.
0
 

Author Comment

by:jskfan
ID: 38735635
by  the way , Passive interface in EIGRP blocks the incoming and outgoing advertisement.
What I have concluded from reading on the Net, is some routers version will advertize EIGRP with the classfull IP adress by default when you redistribute them into other other Routing Protocols such as OSPF. so the work around is to block the advertizement manually by making the interfaces that connect the ABR to the OSPF as Passive, then for instance, create Access-List that encompass the classless subnets of the EIGRP and Tag them, so that later when you redistribute the EIGRP routes you can use the Route Map to mach the Tag.

*** I might be going too far, but I wanted to make sure that Passive interface will come handy in the case where the router version will advertise the classful network ie, 172.16.10.0 as 172.16.0.0 even when you specify the wild card mask of 0.0.0.255.
0
 
LVL 1

Assisted Solution

by:thpipfh
thpipfh earned 400 total points
ID: 38735969
0
Tutorial: Introduction to Managing a Linux Server

In this tutorial on systemd, we will explore:
-OS/Distro Adoption
-chkconfig and Other Legacy Commands
-Summary and Key Commands

 

Author Comment

by:jskfan
ID: 38739330
thpipfh: I have been to that link before I posted the Question. Thank you though.

What I need to know, in case you want to redistribute Classles IP address of a subnet from EIGRP AS to OSPF when the router version(in the EIGRP AS) does allow only the classful subnet.

because in some version if you type for example : Network 10.24.24.0 ?
the help does not show the wild card mask to enter.
what s the work around ?
0
 
LVL 1

Expert Comment

by:thpipfh
ID: 38739704
Please give me what model device you are using ??
0
 
LVL 1

Expert Comment

by:thpipfh
ID: 38739706
what is the ios vertion ?
0
 

Author Comment

by:jskfan
ID: 38747467
If you have seen CBT Nuggets CCIE videos Advanced OSPF configuration. the instructor, had to use the passive interfaces to prevent the router from advertizing EIGRP domain routes, because the ASBR allow only classful IP addresses from EIGRP
So he used passive interfaces, then as a work around he used access-list that permits the /24 subnets mixing it up with Tags and Route maps.. it is not really clear to me...but that would be helpful if any Cisco expert out there can elaborate on that with an example
0
 
LVL 17

Assisted Solution

by:pergr
pergr earned 800 total points
ID: 38761968
Passive interface has nothing to do with redistributing routes between OSPF and EIGRP.

Also, passive interface has nothing to do with traffic (one way traffic).

To make an interface 'passive' in EIGRP (or OSPF) means that the router will not send or receive any EIGRP/OSPF 'hello' packets on that interface, and consequently the router will not form any EIGRP (or OSPF) neighbor relations ships on that interface.

However, the router will advertise the network that is configured on the passive interface to other neighbors - neighbors formed on other interfaces.
0
 
LVL 17

Accepted Solution

by:
pergr earned 800 total points
ID: 38762236
PS. An alternative to use Passive interface, is to redistribute connected subnets, with a filter for just that interface network. With OSPF that gives an external route, while with passive it is an internal route.
0
 
LVL 17

Assisted Solution

by:TimotiSt
TimotiSt earned 400 total points
ID: 38762448
Agree with pergr: you don't even need to configure S0/1 and E0 to run EIGRP to do redistribution.
Also, what type is area 3?
0
 

Author Closing Comment

by:jskfan
ID: 38764259
Thank you
0

Featured Post

Percona Live Europe 2017 | Sep 25 - 27, 2017

The Percona Live Open Source Database Conference Europe 2017 is the premier event for the diverse and active European open source database community, as well as businesses that develop and use open source database software.

Question has a verified solution.

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

Most of the applications these days are on Cloud. Cloud is ubiquitous with many service providers in the market. Since it has many benefits such as cost reduction, software updates, remote access, disaster recovery and much more.
This article is in regards to the Cisco QSFP-4SFP10G-CU1M cables, which are designed to uplink/downlink 40GB ports to 10GB SFP ports. I recently experienced this and found very little configuration documentation on how these are supposed to be confi…
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
Monitoring a network: why having a policy is the best policy? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the enormous benefits of having a policy-based approach when monitoring medium and large networks. Software utilized in this v…
Suggested Courses
Course of the Month8 days, 16 hours left to enroll

764 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