[c-nsp] OSPF VS ISIS

Wayne Xiao Wayne.Xiao at igindex.co.uk
Mon Feb 27 09:19:31 EST 2006

To achieve fast convergence after a link or router failure, your network
need to be able to detect the failures quickly and react to it quickly.
Strike a balance between recovery speed and network stability. The OSPF
default value is way too conservative/slow.

Some techniques I used in my network to achieve fast convergence:

1. use ether-channel. If one physical link down, no convergence happen
2. design network to have 2 equal cost routes over 2 links, if one link
down, 0 second converge time
3. For router to router connection, use direct cable connection as
possible as I can. If a link fails, 0 second to detect it. 
4. For Ethernet and above speed connection, configure OSPF keepalive
timer to sub-second (if it's not WAN link).
5. tune the OSPF timer:
	timers throttle spf 10 100 5000
	timers throttle lsa all 10 100 5000
	timers lsa arrival 80

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Vincent De
Sent: 27 February 2006 13:46
To: 'Oliver Boehmer (oboehmer)'
Cc: cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] OSPF VS ISIS

> But in a properly designed network, both protocols can converge in 
> sub-second..

My OSPF network is far from converging sub-second (so according to you
it is far from being properly designed - fine, I can take criticism :)

First of all, link failure on Ethernet links takes 30 to 40 seconds to
detect... is there anyway to speed this up?

Then, even after failure detection, I have the feeling it still takes 3
to 5 seconds to converge...

What am I doing wrong?


cisco-nsp mailing list  cisco-nsp at puck.nether.net
archive at http://puck.nether.net/pipermail/cisco-nsp/

The information contained in this email is strictly confidential and for the use of the addressee only, unless otherwise indicated. If you are not the intended recipient, please do not read, copy, use or disclose to others this message or any attachment. Please also notify the sender by replying to this email or by telephone +44 (0)20 7896 0011 and then delete the email and any copies of it. Opinions, conclusions (etc.) that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.  IG Markets Limited and IG Index Plc are authorised and regulated by the Financial Services Authority and, in Australia, by the Australian Securities and Investments Commission.

More information about the cisco-nsp mailing list