# Multicast PIM Bootstrap (BSR)
**URL:** https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340
**Category:** Lessons Discussion
**Created:** [December 29, 2016, 9:17pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340 "2016-12-29T21:17:31Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 29, 2016, 9:17pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/1 "2016-12-29T21:17:31Z")
This topic is to discuss the following lesson:
[https://networklessons.com/cisco/ccie-enterprise-infrastructuremulticast-pim-bootstrap-bsr/](https://networklessons.com/cisco/ccie-enterprise-infrastructuremulticast-pim-bootstrap-bsr/)
---
### Author:  [@suman\_grover](https://forum.networklessons.com/u/suman_grover)
#### Post date: [May 18, 2016, 7:27pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/2 "2016-05-18T19:27:36Z")
Why is hop-by-hop messaging different from dense mode flooding ?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [May 21, 2016, 2:19pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/3 "2016-05-21T14:19:43Z")
Hi Suman,
With dense mode flooding, the router will flood the original IP multicast packet that it receives on one interface on other PIM enabled interfaces.
The hop-by-hop behavior of BSR is a bit similar but these packets have a TTL of 1. When the router receives these packets, it replicates the receiving packet and sends a new packet (with the same information) on its PIM enabled interfaces.
Rene
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### Author:  [@mvdroest](https://forum.networklessons.com/u/mvdroest)
#### Post date: [June 13, 2016, 8:27am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/4 "2016-06-13T08:27:45Z")
Hi Rene,
Super lesson. Just noticed the first picture as the wrong pim multicast adress 224.0.1.13 instead of 224.0.0.13.
Maikel
---
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [June 21, 2016, 5:47pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/5 "2016-06-21T17:47:02Z")
Thanks Maikel, just fixed it.
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### Author:  [@nagenderkaushik](https://forum.networklessons.com/u/nagenderkaushik)
#### Post date: [August 30, 2016, 12:39pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/6 "2016-08-30T12:39:06Z")
Hi Rene,
I have another question for you. I notice that each time BSR candidate configuration is created, a new tunnel is created? Can you please elaborate?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 30, 2016, 3:06pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/7 "2016-08-30T15:06:26Z")
Hi Nagender,
These tunnel interfaces are used to communicate with the RP. You can see some examples here:
[IP PIM Sparse Mode](https://networklessons.com/cisco/ccie-enterprise-infrastructuremulticast-pim-sparse-mode/)
Rene
---
### Author:  [@chrisnewnham17](https://forum.networklessons.com/u/chrisnewnham17)
#### Post date: [July 21, 2017, 8:33am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/10 "2017-07-21T08:33:19Z")
Got a question about the hash mask - wouldn’t it always be best to use a 31 bit hash mask?
That way one group will be assigned per RP, then it “rolls over” back to the first RP etc.
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [August 4, 2017, 6:28am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/11 "2017-08-04T06:28:13Z")
Hi Chris,
If you set it to /32, you will have one group per RPR. If you use /31, each RP will have two groups.
Rene
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### Author:  [@dongquangminh](https://forum.networklessons.com/u/dongquangminh)
#### Post date: [April 8, 2018, 10:06am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/12 "2018-04-08T10:06:28Z")
Hi Rene,
I have one question. Can we implement both RP & BSR on the same router? Also, can we do the same thing with Cisco Auto-RP (RP & Mapping Agent on the same router)?
Thank you,
Minh
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [April 13, 2018, 6:42pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/13 "2018-04-13T18:42:36Z")
Hello Minh,
You can enable Auto-RP & BSR (and static RP) on the same router yes. Here’s a quick example:
```
R1#show ip pim rp mapping
PIM Group-to-RP Mappings
Group(s) 224.0.0.0/4
RP 2.2.2.2 (?), v2v1
Info source: 2.2.2.2 (?), elected via Auto-RP
Uptime: 00:00:23, expires: 00:02:32
RP 4.4.4.4 (?), v2
Info source: 4.4.4.4 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:02:11, expires: 00:02:11
```
R2 advertises itself as an RP with Auto-RP, R4 with BSR. R1 seems to prefer Auto-RP.
Interesting to know is that with RP selection, the router prefers RPs that were learned through Auto-RP or BSR over static RPs!
There’s not really a reason to use both Auto-RP and BSR but technically, you could use AutoRP to serve a set of multicast groups and BSR another set of multicast groups.
Running the Auto RP and mapping agent on the same router is no problem, on small networks (and labs) I usually do this.
Rene
---
### Author:  [@michaeldemarco3](https://forum.networklessons.com/u/michaeldemarco3)
#### Post date: [July 12, 2018, 5:22pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/14 "2018-07-12T17:22:40Z")
Hi Rene,
The lab that I have created seems to conflict with the second determining factor you have listed, used to select the RP for a particular group. The RP with the lowest priority (default 0) wins the election.
```
R4#sho ip pim rp-hash 224.0.0.0
RP 150.1.10.10 (?), v2
Info source: 150.1.5.5 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:05:53, expires: 00:01:38
PIMv2 Hash Value (mask 0.0.0.0)
RP 150.1.10.10, via bootstrap, priority 0, hash value 884179440
RP 150.1.8.8, via bootstrap, priority 0, hash value 613026582
R4#sho ip pim rp-hash 224.0.0.0
RP 150.1.8.8 (?), v2
Info source: 150.1.5.5 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:22:06, expires: 00:02:23
PIMv2 Hash Value (mask 0.0.0.0)
RP 150.1.8.8, via bootstrap, priority 0, hash value 613026582
RP 150.1.10.10, via bootstrap, priority 10, hash value 884179440
```
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### Author:  [@alex.fritzsche](https://forum.networklessons.com/u/alex.fritzsche)
#### Post date: [July 18, 2018, 7:51am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/15 "2018-07-18T07:51:41Z")
Hi Michael,
that confused me too, so i read RFC5059 stating:
“BSR Priority
Contains the BSR priority value of the included BSR. This field
is considered as a high-order byte when comparing BSR addresses.
BSRs should by default set this field to 64. Note that for
historical reasons, the highest BSR priority is 255 (the higher
the better), whereas the highest RP Priority (see below) is 0
(the lower the better).”
Summary:
**- BSR election: higher priority wins**
**- RP election: lower priority wins!**
---
### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [July 20, 2018, 4:01pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/16 "2018-07-20T16:01:39Z")
Hello Michael
When an election for RP takes place in a particular group, the priority values exchanged are indeed used as part of the process determine the RP. Once the election is complete, even if you change the priority values, a re-election will not take place. A re-election will only take place if the RP has been detected to have gone down, after the appropriate timers expire. In order to achieve a reelection in your topology, disable the current RP router (reboot or turn off for an extended period of time) and the reelection process will eventually kick in, using the currently configured parameters.
More info about the election and reelection process can be found at [RFC 5059](https://www.ietf.org/rfc/rfc5059.txt).
I hope this has been helpful!
Laz
---
### Author:  [@vinod.kr.agrahari](https://forum.networklessons.com/u/vinod.kr.agrahari)
#### Post date: [August 5, 2018, 1:45am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/17 "2018-08-05T01:45:35Z")
Thanks for explanation ..I see just typo error R1 ( instead of R2) while configuring rp-candidate
---
### Author:  [@rshummoo](https://forum.networklessons.com/u/rshummoo)
#### Post date: [September 14, 2018, 9:16pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/18 "2018-09-14T21:16:27Z")
simply outstanding
Thanks
---
### Author:  [@sijisusan.babu](https://forum.networklessons.com/u/sijisusan.babu)
#### Post date: [December 5, 2018, 6:30am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/19 "2018-12-05T06:30:18Z")
Hi Rene,
I have a doubt. Here R4 also gets BSR messages from BSR. But sparse mode is enabled on all routers. Then how R4 gets BSR message from R3?
Or is that what hop-by-hop basis means? In case of BSR selection, messages will be send to all the routers?
---
### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [December 13, 2018, 5:23pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/20 "2018-12-13T17:23:42Z")
Hello Siji
Sparse mode allows all multicast traffic to first go to the RP and then be sent to the clients that requested it. However, with BSR, we don’t yet have an RP, so sparse mode is not yet enabled. Secondly, the specific BSR message is sent with a TTL of 1 so it is already limited in scope to only next hop routers. That’s what hop-by-hop refers to. Each router then regenerates the BSR out of all PIM enabled interfaces.
I hope this has been helpful!
Laz
---
### Author:  [@sijisusan.babu](https://forum.networklessons.com/u/sijisusan.babu)
#### Post date: [December 17, 2018, 6:05am UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/21 "2018-12-17T06:05:22Z")
Thanks for the info. Got it clear.
---
### Author:  [@aymanlabib](https://forum.networklessons.com/u/aymanlabib)
#### Post date: [June 3, 2019, 3:44pm UTC](https://forum.networklessons.com/t/multicast-pim-bootstrap-bsr/1340/22 "2019-06-03T15:44:23Z")
The first line is R2 and the remaining lines are R1.
Should all be R2
R2(config)#interface Loopback 0
R1(config-if)#ip address 2.2.2.2 255.255.255.255
R1(config-if)#ip pim sparse-mode
```
R1(config)#router ospf 1
R1(config-router)#network 2.2.2.2 0.0.0.0 area 0
```
Now we can use the BSR command:
```
R1(config)#ip pim bsr-candidate loopback 0 ?
Hash Mask length for RP selection
```
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