IGP choice

marcel.duregards at yahoo.fr marcel.duregards at yahoo.fr
Fri Oct 23 09:00:17 UTC 2015

by having multiple areas, therefore ABR which deny routers and network 
LSA, you introduce summarization (ABR only send summary LSA, mean subnet 
info, not topology info) in your network.
Thus you loose informations and do not have a complete topology of your 
network. I guess MPLS/TE prefer to seat on top of a real topology ?

On 22.10.2015 23:22, Bill Blackford wrote:
> I don't have all the details because I don't fully understand it, but I've
> heard that if you're running an MPLS/RSVP core, you can only use a single
> OSPF area. This introduces a scalability ceiling.
> On Thu, Oct 22, 2015 at 12:35 PM, Dave Bell <me at geordish.org> wrote:
>> On 22 October 2015 at 19:41, Mark Tinka <mark.tinka at seacom.mu> wrote:
>>> The "everything must connect to Area 0" requirement of OSPF was limiting
>>> for me back in 2008.
>> I'm unsure if this is a serious argument, but its such a poor point
>> today. Everything has to be connected to a level 2 in IS-IS. If you
>> want a flat area 0 network in OSPF, go nuts. As long as you are
>> sensible about what you put in your IGP, both IS-IS and OSPF scale
>> very well.
>> The differences between the two protocols are so small, that people
>> really grasp at straws when 'proving' that one is better over the
>> other. 'IS-IS doesn't work over IP, so its more secure'. 'IS-IS uses
>> TLVs so new features are quicker to implement'. While these may be
>> vaguely valid arguments, they don't hold much water. If you don't
>> secure your routers to bad actors forming OSPF adjacencies with you,
>> you're doing something wrong.Who is running code that is so bleeding
>> edge that feature X might be available for IS-IS, but not OSPF?
>> Chose whichever you and your operational team are most comfortable
>> with, and run with it.
>> Regards,
>> Dave

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