From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Thu Dec 08 2005 - 03:19:51 GMT-3
Hi Andrew ,
Some additions to what Paresh has listed .
Notes on ATT Bit : ( Its never set manually )
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When ATT Bit will be set
1) L1/L2 routers will set the ATT bit in their L1 LS Protocol Data Units
(PDUs) to indicate that they are a potential exit point from the area.
2)An L1/L2 router sets the ATT bit only if it has visibility of other area
IDs in its L2 LSDB:
Pls Note : If an L1/L2 router is not directly connected to another area but
will still have visibility of other areas in its L2 LSDB. Then also it will
set the ATT bit in its L1 LSP.
Notes on Overload Bit .
~~~~~~~~~~~~~~~~~~~~
Much of it explained in Paresh Mail . However I am outlining the scenarios
during which you need to turn on this knob .
1) a test router in the lab, connected to a production network;
2) a router configured as an LSP flooding server, for example, on a
Nonbroadcast Multi-access (NBMA) network, in combination with the mesh-group
feature, and a router that is aggregating Virtual Circuits (VCs) used only
for network management
3) A gateway router could set the overload bit till the time BGP peering
will have to come up ( up on startup ) !!!
Thanks and Regards
Arun
----- Original Message -----
From: "Andrew Lissitz (alissitz)" <alissitz@cisco.com>
To: "Paresh Khatri" <Paresh.Khatri@aapt.com.au>; <comserv@groupstudy.com>;
<ccielab@groupstudy.com>
Sent: Thursday, December 08, 2005 10:56 AM
Subject: RE: ISIS - set-attached-bit and set-overload-bit
> Paresh you rock! I am going to try this now, thanks
>
>
> -----Original Message-----
> From: Paresh Khatri [mailto:Paresh.Khatri@aapt.com.au]
> Sent: Thursday, December 08, 2005 12:23 AM
> To: Andrew Lissitz (alissitz); comserv@groupstudy.com;
ccielab@groupstudy.com
> Subject: RE: ISIS - set-attached-bit and set-overload-bit
>
> Hi Andrew,
>
> I don't believe that you can use the 'set-attached-bit' command when using
ISIS for routing IP; while the ATT bit is also used by IP, you can only set
it via this command when routing CLNS via ISIS.
>
> As for the second command, one possible way a question could require you
to use this is: configure your interior routers so that they do not
advertise themselves as available for transit routing until BGP has
converged on these routers. Or: configure your interior routers so that
they do advertise themselves as available for transit routing until 2
minutes after the IGP routing process has started.
>
> Here's my little summary of how you can use the set-overload-bit command:
>
> set-overload-bit
> ' immediately and unconditionally sets the overload bit
>
> set-overload-bit on-startup <seconds>
> ' sets the overload bit on startup for the specified number of seconds
(from 5 to 86400)
>
> set-overload-bit on-startup <seconds> suppress interlevel
> ' sets the overload bit on startup for the specified number of seconds
(from 5 to 86400). Suppresses advertisement of any inter-level routes while
the overload bit is set.
>
> set-overload-bit on-startup <seconds> suppress external
> ' sets the overload bit on startup for the specified number of seconds
(from 5 to 86400). Suppresses advertisement of any redistributed routes
while the overload bit is set.
>
> set-overload-bit on-startup <seconds> suppress interlevel external
> ' sets the overload bit on startup for the specified number of seconds
(from 5 to 86400). Suppresses advertisement of any inter-level or external
routes while the overload bit is set.
>
> set-overload-bit on-startup wait-for-bgp
> ' sets the overload bit on startup. It's cleared on receiving a signal
from BGP or after 10 minutes, whichever comes first.
>
> set-overload-bit on-startup wait-for-bgp suppress interlevel
> ' sets the overload bit on startup. It's cleared on receiving a signal
from BGP or after 10 minutes, whichever comes first. Suppresses
advertisement of any inter-level routes while the overload bit is set.
>
> set-overload-bit on-startup wait-for-bgp suppress external
> ' sets the overload bit on startup. It's cleared on receiving a signal
from BGP or after 10 minutes, whichever comes first. Suppresses
advertisement of any redistributed routes while the overload bit is set.
>
> set-overload-bit on-startup wait-for-bgp suppress interlevel external
> ' sets the overload bit on startup. It's cleared on receiving a signal
from BGP or after 10 minutes, whichever comes first. Suppresses
advertisement of any inter-level or external routes while the overload bit
is set.
>
> set-overload-bit suppress interlevel
> ' immediately and unconditionally sets the overload bit. Suppresses
advertisement of any inter-level routes while the overload bit is set.
>
> set-overload-bit suppress external
> ' immediately and unconditionally sets the overload bit. Suppresses
advertisement of any external routes while the overload bit is set.
>
> set-overload-bit suppress interlevel external
> ' immediately and unconditionally sets the overload bit. Suppresses
advertisement of any inter-level or redistributed routes while the overload
bit is set.
>
> HTH,
> Paresh.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Andrew Lissitz (alissitz)
> Sent: Thursday, 08 December 2005 03:01 PM
> To: comserv@groupstudy.com; ccielab@groupstudy.com
> Subject: ISIS - set-attached-bit and set-overload-bit
>
>
> Hello group,
>
> I am trying to think of a scenario / question that may cause me to think
of this feature.
>
> pe1(config)#router isis
> pe1(config-router)#?
> set-attached-bit Conditionally advertise us as attached to L2
> set-overload-bit Signal other routers not to use us in SPF
> pe1(config-router)#
>
> My lab:
>
> R1 <---> R2 (My lab follows the 'KISS' design guide)
>
> Has anyone used these features and or can think of a question / scenario
that would cause me to look at this feature for the solution. I am really
trying to think of how a question / scenario could be written.
> Kindest regards group,
>
> Andrew
>
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