From: Andrew Lissitz \(alissitz\) (alissitz@cisco.com)
Date: Mon Oct 17 2005 - 17:41:11 GMT-3
Thanks Kamrul! Good Stuff ... and good to know
-----Original Message-----
From: kamrul.islam@bell.ca [mailto:kamrul.islam@bell.ca]
Sent: Monday, October 17, 2005 4:32 PM
To: Andrew Lissitz (alissitz); swm@emanon.com;
nettable_walker@hotmail.com; ccielab@groupstudy.com
Cc: comserv@groupstudy.com
Subject: RE: max-metric router-lsa on-startup wait-for-bgp
Hi Andrew,
I think we're pretty much close of our understanding of this feature.
The feature we're talking about has three options and mainly used for
network fast convergence but their purposes are different.
1. "max-metric router-lsa" - this option is used to gracefully shutting
down the router. With this option when a router is taking for
maintenance the neighbour routers would not wait for ospf hold timers to
expire instead neighbours forward traffic through other node and in
results we'll get minimum packets drop. One important point you outlined
we shouldn't save this config when bringing up the router.
2. "max-metric router-lsa on-startup <announce-time>" - which is being
used for MPLS-LDP/TDP-IGP synchronization purpose to avoid black-hole
issue which I've described in my previous note. MPLS traffic engineering
also helps to stop the same black hole issue.
3. "max-metric router-lsa on-startup wait-for-bgp" - this option is well
described in the link you forwarded.
Kindest regards.
Kamrul.
-----Original Message-----
From: Andrew Lissitz (alissitz) [mailto:alissitz@cisco.com]
Sent: October 17, 2005 2:33 PM
To: Islam, Kamrul (4001782); swm@emanon.com;
nettable_walker@hotmail.com; ccielab@groupstudy.com
Cc: comserv@groupstudy.com
Subject: RE: max-metric router-lsa on-startup wait-for-bgp
Here is a link to this (watch for word wrap):
http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_
guide09186a0080087c09.html#wp1015359
I did not see much reference to MPLS, tags will be assigned based on IGP
routes, and this appears to be more related to BGP convergence and
adding / removing routers from OSPF networks.
Here is the description from the web page:
Feature Overview
The OSPF Stub Router Advertisement feature allows you to bring a new
router into a network without immediately routing traffic through the
new router and allows you to gracefully shut down or reload a router
without dropping packets that are destined for other networks. This
feature introduces three configuration options that allow you to
configure a router that is running the Open Shortest Path First (OSPF)
protocol to advertise a maximum or infinite metric to all neighbors.
Important Note? Note: You should not save the running configuration of
a router when it is configured for a graceful shutdown because the
router will continue to advertise a maximum metric after it is reloaded.
Pretty cool feature!
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
kamrul.islam@bell.ca
Sent: Monday, October 17, 2005 12:36 PM
To: Andrew Lissitz (alissitz); swm@emanon.com;
nettable_walker@hotmail.com; ccielab@groupstudy.com
Cc: comserv@groupstudy.com
Subject: RE: max-metric router-lsa on-startup wait-for-bgp
I know the command line "max-metric router-lsa on-startup 200" (say 200
sec, slightly different than yours) can be used to address the
black-hole issue in MPLS tag switching. Example, in MPLS environment
when a P or PE router fails and then comes back, normally IGP (OSPF or
ISIS) comes up first and then it forms TDP/LDP relationship to it's
neighbours. There is a time gap between the OSPF and TDP/LDP neighbour
relationship built with the neighbouring routers. As soon IGP comes up
traffic from the neighbour routers start push to use the new node (of
course if IGP cost is lower through the new node compare to other
existing nodes), for some period of times all traffic using the new node
will be dropped until TDP/LDP neighbour relationship is formed on that P
or PE router
Using the command line "max-metric router-lsa on-startup 200", router
sends OSPF LSA to it's neighbours and say don't forward any traffic to
me within 200 seconds although my OSPF neighbours are built. So when a
router boots up it will have enough time to form TDP/LDP relationship to
its neighbours and thus protect black-holing traffic in mpls network.
Thanks,
Kamrul.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Andrew Lissitz (alissitz)
Sent: October 17, 2005 10:28 AM
To: Scott Morris; 3x CCIE; ccielab@groupstudy.com
Cc: C&S GroupStudy
Subject: RE: max-metric router-lsa on-startup wait-for-bgp
I have not seen this command for MPLS PEs or Ps... (does not mean much
... I just have not seen it in my work). I have seen this being
deployed though:
MPLS LDP-IGP Synchronization
http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_
guide09186a00802d95dd.html
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Morris
Sent: Monday, October 17, 2005 8:30 AM
To: '3x CCIE'; ccielab@groupstudy.com
Subject: RE: max-metric router-lsa on-startup wait-for-bgp
IMHO this would be used on a P (maybe PE?) router in an MPLS
implementation.
For the R&S lab I don't believe it has any useful purpose.
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
3x CCIE
Sent: Monday, October 17, 2005 1:58 AM
To: ccielab@groupstudy.com
Subject: max-metric router-lsa on-startup wait-for-bgp
These are the things you wonder about @ 1:00am after a day of studying
for CCIE #3 & watching both the Bears & White Sox win
Has anyone ever seen this command used in real production ?
router ospf 10
max-metric router-lsa on-startup wait-for-bgp
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