02-10-2012 02:58 AM - edited 03-04-2019 03:13 PM
How Eigrp works??
What does mean no auto-summary and passive interface command??
Anyone explain me briefly to understand.
And also explain me how OSPF works??
02-10-2012 03:48 AM
Hi,
to understand EIGRP I would look at Cisco Doc and for OSPF also at Cisco Doc and at the RFC.
But basically no autosummary means do not automatically summarize the subnet you're going to advertize when crossing a major network boundary, this is now default on latest IOS versions and passive interface means do not establish a neighbour relationship on this link but advertise the subnet anyway.
http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1ceigrp.html
http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cospf.html
http://www.networksorcery.com/enp/protocol/ospf.htm
Regards.
Alain
02-10-2012 04:44 AM
Hi Dinesh,
Let me give a small scenario to know how that eigrp no-auto summary will work.
Imagine a campus network. the entire network functions within the 10.0.0.0/8 space internally. you're going to use vlsm to break the network up into different subnets as needed (/30's or /31's for point-to-point links, /23 or /24 for user access, etc.).
routing protocols automatically summarize the networks they advertise (i.e. your router wouldn't care if you had 10.0.1.0/24, 10.1.0.0/24, and 10.100.1.0/24 in your routing table, it would advertise one route -- 10.0.0.0/8). when every router is trying to do this -- they all eventually begin to get confused because they all have routes to the same destination (10.0.0.0/8) but no "more specific" prefix information is carried
And you would use no auto-summary when you require carrying traffic that originates from a subnetted subnet to keep its classless address across the neighbor router. It's usually not an issue when neighbor routers share the same subnetted address space on their interfaces.
Regarding passive interface command:
With EIGRP running on a network, the passive-interface command stops both outgoing and incoming routing updates, since the effect of the command causes the router to stop sending and receiving hello packets over an interface.
You can see the below link for how this works
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f0a.shtml
Hope the above clear and understand you.
Please rate all the helpfull posts.
Regards,
Naidu.
02-11-2012 04:12 AM
Thank u very much.
Can u explain me How eigrp works with diagram.
I interview they ask one question.
How eigrp is better than ospf
can u tell me.
02-12-2012 10:33 PM
Hi Dinesh,
See the below link for EIGRP no auto summary.
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094cb7.shtml#auto
Read the below link for EIGRP passive interface.
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f0a.shtml
Hope the above clear and understand you.
Please rate all the helpfull posts.
Regards,
Naidu.
02-13-2012 12:25 AM
Hello Dinesh,
I would like to add on the interview question - How EIGRP is better than OSPF.
1) My strategy to respond to that question would have been - It's basically a design practice followed by an organization. So, comparing EIGRP with OSPF or vice-versa may not be genuine. But still for the sake of discussion, i would feel below points which gives an edge to EIGRP over OSPF.
If you look at the above, you wouldn't see much of an advantage apart from summarization & unequal cost load balancing. So, it's frankly unfair to question which is better as per me.
Thanks
Vivek
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