largest OSPF core

Warren Kumari warren at
Fri Sep 3 15:22:15 UTC 2010

On Sep 2, 2010, at 11:11 AM, Nick Hilliard wrote:

> On 02/09/2010 13:20, lorddoskias wrote:
>> I'm just curious - what is the largest OSPF core (in terms of  
>> number of
>> routers) out there?
> You don't expect anyone to actually admit to something like this? :-)

Of course I do -- 'tis much for your reputation to have wrangled a  
poorly designed, ugly network under control than to have only worked  
at places with smooth sailing.... I *don't* expect the owner /  
designers of these to come forward, rather those who inherited a pile  
of choss to share war stories...  :-P

I worked on a network that had >350 routers in an (non-zero) area.  
Now, ~350 routers in an area doesn't sound *that* impressive, but on  
average these devices had 6 interfaces in OSPF, and many of these  
links were of the form:

[router A]-- {GRE} --- [firewall]-- {GRE in IPSEC} ------- 
[Internet]------- {GRE in IPSEC} ---[firewall]---{GRE} --- [router B]

Routers A and B would form an OSPF adjacency. Much of this was an  
overlay network (over the Internet) and so the firewalls would build  
IPSec tunnels. Of course, said firewalls would not pass OSPF, so we  
had to build GRE tunnels between routers A and D and run OSPF over  
those -- traffic would enter the router, get encapsulated in GRE and  
then the GRE would be encapsulated in IPSec and tossed into the void....
In other places (in the same OSPF area) we would purchase parallel  
T1 / E1s that we would run MLPPP over, and / or plain DS3s.
Oh, did I mention that network was primarily to support international  
call centers that had been outsourced to wherever was *really* cheap,  
and that many places with very cheap labor have very poor  
infrastructure? It was not uncommon to have interfaces that would  
bounce 5 or 10 times a day*....


*: And yes, we did 'ave to get up out of shoebox at twelve o'clock at  
night and lick road clean wit' tongue. We had two bits of cold gravel,  
worked twenty-four hours a day at mill for sixpence every four years,  
and when we got home our Dad would slice us in two wit' bread knife.

> Nick

It's a mistake trying to cheer up camels. You might as well drop  
meringues into a black hole. -- Terry Prachett

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