From: Joseph Brunner (joe@affirmedsystems.com)
Date: Thu May 22 2008 - 19:02:37 ART
I didn't mean that.
I meant if you were relying on learning your rp's via auto rp on SPARSE MODE
ONLY interfaces, and you then
STOPPED auto-rp listner from doing this, you would no longer know those
RP"s. then the groups COULD (if ip pim dm-fallback was permitted)
Revert to dense mode and keep going ;)
I should have made myself clearer. after a the RP's age out (300 seconds if
I recall) they wont be heard again if they were learned via ONLY because you
were running autorp listener, which I was saying could just have been turned
off ;)
-Joe
_____
From: Edison Ortiz [mailto:edisonmortiz@gmail.com]
Sent: Thursday, May 22, 2008 5:58 PM
To: 'Joseph Brunner'; 'lei tian'; 'ccie'
Cc: 'Cisco certification'
Subject: RE: no ip pim dm-fallback vs no ip pim autorp listener
Joe,
I agreed on everything you said, except the below paragraph.
> So to answer the original question, disabling autorp operation on sparse
mode interfaces
> by configuring "no ip pim autorp listener" can cause groups to revert back
to dense mode
> operation (regardless of interface configuration) unless "no ip pim
dm-fallback" is configured.
The 'ip pim autorp listener' is enabled globally and allows the router to
'listen' for the .39 and .40 groups as you stated.
It does not cause groups to revert back to dense mode nor changes groups
from dense to sparse or vice-versa.
Edison Ortiz
Routing and Switching, CCIE # 17943
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Thursday, May 22, 2008 3:33 PM
To: 'lei tian'; 'ccie'
Cc: 'Cisco certification'
Subject: RE: no ip pim dm-fallback vs no ip pim autorp listener
That is not true Lei Tian.
"No ip pim dm-fallback" will not allow groups to flood if an rp is unknown
for the group. The mode you run on the interfaces has nothing to do with how
the group operates... just how the rp discovery/mapping activity takes
place.
Read the univercd
"PIM dense mode fallback is enabled. That is, a multicast group in the
absence of rendezvous point (RP) information will fall to dense mode,
regardless of the interface mode configuration."
Cont.
"Use this command to prevent a router from falling back into PIM-DM when the
RP becomes unavailable. This command also causes the router to block all
multicast traffic for groups not specifically configured with an RP."
Regarding " ip pim autorp listener"
This command simply enables auto-rp discovery operations over sparse mode
interfaces.
"To cause IP multicast traffic for the two Auto-RP groups 224.0.1.39 and
224.0.1.40 to be Protocol Independent Multicast (PIM) dense mode flooded
across interfaces operating in PIM sparse mode, use the ip pim autorp
listener command in global configuration mode."
So to answer the original question, disabling autorp operation on sparse
mode interfaces by configuring "no ip pim autorp listener" can cause groups
to revert back to dense mode operation (regardless of interface
configuration) unless "no ip pim dm-fallback" is configured.
-Joe
Certified Bullsh*t caller #19366
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of lei
tian
Sent: Thursday, May 22, 2008 3:25 PM
To: ccie
Cc: Cisco certification
Subject: Re: no ip pim dm-fallback vs no ip pim autorp listener
Hi Amin,
no ip pim dm-fallback wont do anything if run sparse-mode
no ip pim autorp listener will disable autorp listener,
If you are using autorp then you need to configure dummy RP for two group.
If you are using static RP then this command doesnt do anything.
Thanks
Lei
On Thu, May 22, 2008 at 3:16 PM, ccie <ccie@just-horizon.com> wrote:
> Hello experts,
>
>
>
> What would be the difference in the result if of these two commands if I
> run
> pim sparse-mode
>
> no ip pim dm-fallback
>
> vs
>
> no ip pim autorp listener
>
>
>
> Regards,
>
> Amin
>
>
> _______________________________________________________________________
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