I'm personally aware of dozens and dozens of OSPF deployments, but not aware of a single IS-IS deployment. This is among smaller consumer ISPs, with typically up to around 10K customers.

I'm sure a big reason for this is that IS-IS support isn't all that common in the lower end routing gear often used by these providers.

On Fri, Jan 25, 2019, 7:16 AM Steven Bahnsen <sbahnsen20@gmail.com wrote:

Hi,

First time poster looking for some input on a debate and I apologise if I've
done this completely wrong, but I don't think my colleague will be convinced
until he hears it from this community.

Granted I'm relatively green when it comes to networking, but it was my
understand that other than BGP, the most widely used/implemented IGP would be
OSPF. However, my colleague insists that I'm 100 percent wrong and that is
IS-IS.

I want to be clear, I'm not debating which protocol is better or worse, as they
both have their strengths and weaknesses and ultimately it comes down to several
factors based on a particular use-case on which routing protocol is the best way
forward for a network.

However in saying that, I believe that, when it comes to sheer numbers of where
an IGP is implemented, OSPF is far more widely used in the world today, whether
it be in small to medium to large businesses, Enterprise networks and even
Service Provider networks (where as per my understanding, is where IS-IS really
shines)

I understand that this isn't really quantifiable, but I would like to get the
opinions/experiences from this list and see what the outcome of this question is
out of sheer curiosity.

Thanks!

Steve