From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Fri Oct 13 2006 - 02:44:21 ART
Actually "no ip dm-fallback" will set RP for groups that do no have known RP
to 0.0.0.0
The basis idea here is to prevent dense-mode operation for non-auto RP
groups .Actually you will have to set the interface mode to only sparse-mode
Note : SPARSE-DENSE-MODE do not have any meaning here since Dense mode
operation will never happen if you enable this command . Only exception to
this rule is Auto-RP groups , It is interesting to note that Dense mode
flooding of AUTO-RP groups would still happen even when sparse mode is
configured on interface.
Alternate Strategy on IOS image that do not support this command.
On IOS images that do not support this command pls. follow the following
strategy.
1) Configure all PIM interface with sparse-dense-mode
2) Configure any of the loopback interface as static rp( WITHOUT
OVERRIDE command ) for all groups except auto-rp groups
When you do this router will behave the same way as when you turned on " no
ip dm-fallback" command .
Hope this helps.
Thanks and Regards
Arun
----- Original Message -----
From: "Jung-I Lin" <easyman.lin@gmail.com>
To: "STEELFIN" <steelfin@gmail.com>
Cc: <ccielab@groupstudy.com>
Sent: Friday, October 13, 2006 6:01 AM
Subject: Re: no ip pim dm-fallback
> Hi, STEELFIN
> This command is introduced in ver 12.3(4)T.
> You might not see this command in your IOS version 12.3(20).
>
> As you can see this command is use to prevent "falling backup to
> dense-mode".
> What would cause a router falling back to dense-mode?
> If the interface are in sparse-only-mode, it rely on RP(staticly or
> dynamically) to join/transmit to the group.
> If no RP exist for that group, then it is unable to join/transmit to the
> group.
>
> But if the interface is in sparse-dense-mode, it will switch the group to
> dense-mode operation if the rp fails or not exist for that group.
>
> The dm-fallback command is used in this situation, if you do not want the
> router switch to dense-mode while the interface is configured in
> "sparse-dense-mode".
> You can issue "no ip pim dm-fallback". (This command is on by default)
>
> Note this command will not affect the two "auto-rp" group
> 224.0.1.39/224.0.1.40.
> These two group will always in dense-mode(if you configured
sparse-dense-mod
> on interfaces).
>
> HTH.
>
> On 10/13/06, STEELFIN <steelfin@gmail.com> wrote:
> >
> > Hi
> >
> > Is the "no ip pim dm-fallback" command used with sparse mode ? All of
the
> > documentation I read state that it is a command and should be entered on
> > all
> > sparse-mode routers to prevent fallback to dense mode in the event of RP
> > failure.
> >
> > I am unable to enter this command :
> >
> > ROM: System Bootstrap, Version 12.2(7r) [cmong 7r], RELEASE SOFTWARE
(fc1)
> > ROM: C2600 Software (C2600-ADVENTERPRISEK9-M), Version 12.3(20), RELEASE
> > SOFTWARE (fc2)
> >
> > R2(config)#no ip pim ?
> > accept-register Registers accept filter
> > accept-rp RP accept filter
> > autorp Configure AutoRP global operations
> > bidir-enable Enable Bidir-PIM
> > bsr-candidate Candidate bootstrap router (candidate BSR)
> > log-neighbor-changes Log PIM neighbor up/down and DR changes
> > register-rate-limit Rate limit for PIM data registers
> > register-source Source address for PIM Register
> > rp-address PIM RP-address (Rendezvous Point)
> > rp-announce-filter Auto-RP announce message filter
> > rp-candidate To be a PIMv2 RP candidate
> > send-rp-announce Auto-RP send RP announcement
> > send-rp-discovery Auto-RP send RP discovery message (as RP-mapping
> > agent)
> > spt-threshold Source-tree switching threshold
> > ssm Configure Source Specific Multicast
> > state-refresh PIM DM State-Refresh configuration
> > vrf Select VPN Routing/Forwarding instance
> >
> > Is this command no longer available?
> >
> > Thank you
> >
> > SF
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
>
>
>
> --
> Thanks
> Best Regards,
>
> Jung-I Lin
>
> _______________________________________________________________________
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> http://www.groupstudy.com/list/CCIELab.html
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