From: Carlos Alberto Trujillo Jimenez (carlos.trujillo.jimenez@gmail.com)
Date: Thu Mar 20 2008 - 20:31:32 ART
Matt.
Asnwering your questions, well it depends about several factors... like for
example: Is there a single candidate rp or there will be more than one rp?,
if there will be more than one rp, both will be the rps for the same group?,
or one will be the rp for one group? and the other will be the rp for
another group?
You must keep all this options in mind, before implementing a solutions
using the mentioned commands.
each of those commands is selected to act in certain scenarios, but not in
all.. I try to mean that sometimes in some sort of topologys them applies
and in others not.
Back to your requirements:
> When I want to
> specifically assign a certain group to a certain RP, do I have to make
> that
> specification with which of these commands?
>
> 1. ip pim rp-announce-filter rp-list 1 group-list 2 on the Mapping Agent
> 2. ip pim send-rp-announce l0 scope 16 group-list 1 on the Candidate RP
EXAMPLE 1:
2 Candidate RPS, each candidate RP for a DIFFERENT GROUP:
You MUST only set the option 2 in each candidate RP router with the
access-list matching a different group that will be serviced in each router.
2. ip pim send-rp-announce l0 scope 16 group-list 1 on the Candidate RP
As a result each PIM router will know about both RPS each one for a
different group.
r3#show ip pim rp mapping
Group(s) 225.0.0.0/8
RP 170.18.102.1 (?), v2v1
Info source: 170.18.102.1 (?), elected via Auto-RP
Uptime: 00:00:43, expires: 00:02:13
Group(s) 227.0.0.0/13
RP 170.18.103.1 (?), v2v1
Info source: 170.18.103.1 (?), elected via Auto-RP
Uptime: 00:00:17, expires: 00:02:38
EXAMPLE 2: 2 Candidate RPS, each candidate RP for THE SAME GROUP:
You can limit at the Mapping Agent who will be the RP propagated to the PIM
ROUTERS by using option 1 command.
1. ip pim rp-announce-filter rp-list 1 group-list 2 on the Mapping Agent
NOW, LETS LOOK AT A REAL SCENARIO THE USE OF BOTH COMMANDS.
[R3]---------------------------------------------------------[R2]
ip 3.3.3.3 ip 2.2.2.2
M.A. Candidate
RP Candidate RP
group 227.0.0.0/24 group 227.0.0.0/24
group 225.0.0.0/24
EXAMPLE 1:
You want R3 to be the RP FOR GROUPS 225.0.0.0/24 AND 227.0.0.0/24
By default R3 will be the RP for both groups because for the mapping agent
when it compares both candidate rps it looks that R3 has a higher ip address
than r2 and by default R3 will be the candidate RP for both groups:
CONFIGURATION:
R3:
ip pim send-rp-announce Loopback103 scope 16 group-list 3
access-list 3 permit 227.0.0.0 0.255.255.25
access-list 3 permit 225.0.0.0 0.255.255.255
ip pim send-rp-discovery Loopback103 scope 16
R2:
ip pim send-rp-announce Loopback102 scope 16 group-list 2
access-list 3 permit 225.0.0.0 0.255.255.25
VERIFICATION:
r3#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent (Loopback103)
Group(s) 225.0.0.0/8
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:00:09, expires: 00:02:51
RP 2.2.2.2 (?), v2v1
Info source: 2.2.2.2 (?), via Auto-RP
Uptime: 00:14:40, expires: 00:02:17
Group(s) 227.0.0.0/13
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:14:10, expires: 00:02:49
r2#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
Group(s) 225.0.0.0/8
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:00:36, expires: 00:02:23
Group(s) 227.0.0.0/13
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:14:38, expires: 00:02:22
AS a result R3 is the ELECTED RP for both groups: 225.0.0.0/24 and 227.0.0
/24
EXAMPLE 2:
For the same DIAGRAM you want so that R3 is the RP ONLY for group
227.0.0.0/24 while R2 is the ONLY RP for group 225.0.0.0/24:
For the same configuration pasted above, you must only add a filter in the
MAPPING AGGENT (R3) to accept only group 227.0.0.0/24 for THE CANDIDATE RP
(R3) only.
R3:
ip pim rp-announce-filter rp-list 13 group-list 73
access-list 13 permit 3.3.3.3
access-list 73 permit 227.0.0.0 0.255.255.255
VERIFICATION:
r2#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
Group(s) 225.0.0.0/8
RP 2.2.2.2 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:00:09, expires: 00:02:49
Group(s) 227.0.0.0/13
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:00:37, expires: 00:02:46
r2#
r3#show ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent (Loopback103)
Group(s) 225.0.0.0/8
RP 2.2.2.2 (?), v2v1
Info source: 2.2.2.2 (?), elected via Auto-RP
Uptime: 00:00:30, expires: 00:02:25
Group(s) 227.0.0.0/13
RP 3.3.3.3 (?), v2v1
Info source: 3.3.3.3 (?), elected via Auto-RP
Uptime: 00:00:58, expires: 00:02:02
r3#
If you compare the output of the "show ip pim rp mapping" in both examples
1 and 2,, you can notice what is the result if we add the command "ip pim
rp-announce...." in the mapping agent.
The *rp-list access-list *defines an access-list of candidate RPs that, if
permitted, are accepted for the multicast ranges specified in the *group-list
access-list *command.
The mapping agent listens to all RP candidate announcements and builds a
table with the information. If several RPs announce themselves for a
multicast group range, the mapping agent chooses only onethe RP with the
highest IP address.
http://www.cisco.com/en/US/tech/tk828/technologies_configuration_example09186
a00801cb923.shtml#filter
Cheers.
2008/3/20, Matt Bentley <mattdbentley@gmail.com>:
>
> Hello:
>
> Quick question for you all. I have tried to implement this on a lab, but
> having trouble finding out exact expected behavior. When I want to
> specifically assign a certain group to a certain RP, do I have to make
> that
> specification with which of these commands?
>
> 1. ip pim rp-announce-filter rp-list 1 group-list 2 on the Mapping Agent
> 2. ip pim send-rp-announce l0 scope 16 group-list 1 on the Candidate RP
>
> Or do I need to do it on both? Also, will only the RPs that are relevant
> to
> groups the router is "participating" in (meaning the ip igmp join/static
> group command was issued on it) show up in the "show ip mroute" output, or
> will ALL RPs show up there? Thanks in advance for all your help.
>
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