Sunday, February 8, 2009

Multicast VPN FAQ

From the last few days a discussion is going on MVPN among me, Chintan Shah (Colt Technologies) & Harold Ritter(Cisco). Consequence lot of hidden concepts come out. So I finally made the faq so that it can be used by others as reference.

Would like to thank hritter for sharing his great experience to us.

MVPN Discussion & FAQ

Q:- Data and Default MDt are based on which draft?
A:- For the data MDT, the method to signal the source address is described in draft-rosen-vpn-mcast section 7.2, which is supported by both IOS and JUNOS.

For the default MDT, the signaling in IOS is done using draft-nalawade-idr-mdt-safi, which is not supported in JUNOS.

Q:- Does MVPN require Sparse Mode Or SSM?
A:- MVPN can be implemented with the both. But in multivendor enviorment like juniper SSM only supports data mdt not default mdt. For implementing default mdt one need to deply anycast rp.

Q:- Does SP need to configure all routers for MSDP?
A:- It depends as per the requirement. If SP is having more traffic in doenstream then those P can be used for MSDP peering. So the answer is no if you are having 10 P routers then out of 10 2 or 2 or 10 can be used for MSDP peering.

Q:- How to announce RP in case of using Anycast RP?
A:- If SP deploys anycast RP address in the core then static RP is the best option. Another option to use the dynaic RP like auto rp or bsr.

Q:- Which type of entries created in SSM & in Anycast RP?
A:- In SSM only S,G entrie is created. In Anycast *,G * S,G entries creared.

Q:- How to use "Ip pim spt threshold infinity" in SP domain?
A:- By default cisco IOs set threshold value to 0. Ip pim spt threshold infinity can be used only with ASM becasue it supports *,G while SSM supports only S,G so it cannot be used with this.

Q:- Does Juniper support auto-rp?
A:- Yes, it is supported by juniper.

Q:- How to provide the redundancy in case of Anycast RP & SSM?
A:- In case of anycast RP if any of the RP fails then the other RP will take care from the RP set. In RP set all the routers configured with the same ip address. In case of SSM no rp is required.

Q:- Cisco IOS MDT SAFI implementation is based on which draft?
A:- The IOS MDT SAFI implementation is based on the following draft.

Q:- Advantage of SSM Vs SM
A:- RP infrastructire is not required in case of SSM but in SM it is mandatory.

Q:- Does P routers participate in maintaining the states?
A:- No, only PE will be used. Core will be free from the states.

Q:- Difference between SSM Vs SM in case of update,register messages?
A:- SSM uses PIM-SM with a few modifications. RFC4601 section 4.8.1 defines the modifications to the PIM SM protocol to support SSM. Beyond these modifications, all normal PIM SM functionality and messages are required, including periodic join messages.

Q:- Can SP use Bi-Dir in core?
A:- Yes, if SP doesnot want to create S,G entries. Bi-dir is used only if SP is having very large number of VPNs.

Q:- Does Cisco/Juniper support bi-dir?
A:- Bi-dir is suported by cisco for all the platforms but juniper doesnot support.

Q:- Does Anycast RP require MSDP?
A:- RFC4610 allows you to run Anycast RP without MSDP by having the RP receiving the register message to replicate this message to the other RP(s) in the RP set. Section 3 of RFC4610 explains this mechanism in details.


Q:- Does cisco support Anycast with MSDP?
A:- Yes

shivlu jain

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Anonymous said...

Nice work overall, keep up this good work. I like to see people covering the SP environments.

alex smith said...

A lot of organisations we deal with have PBXes and are not in a position to just throw them away, so we are seeing a hybrid approach where their PBX is connected across different sites using an vpn

Anonymous said...

some stuff about vpn and proxy

Swapnendu said...

MSDP is the protocol that makes Anycast RP can both NOT be supported by Cisco together..that statement is incorrect..

shivlu jain said...


Absolutely right, MSDP works wither with static or anycast RP. By mistake it was written No. Changes done. Thanks.

shivlu jain

parveen jindgar said...

Does MVPN require Sparse Mode Or SSM?
A:- MVPN can be implemented with the both. But in multivendor enviorment like juniper SSM only supports data mdt not default mdt. For implementing default mdt one need to deply anycast rp.

hi Shivlu sir,
request you clear the above point more i am facing this probelm in my network where i have juniper and cisco.So what needs to be done


parveen jindgar

shivlu jain said...

If you want to utilize the data mdt in MVPN in that case you need to run the sparse mode rather than dense mode. In sparse mode you can use the auto-rp if the cloud is cisco or use the BSR but the best is to deploy SSM because you won't get the *,G entries in that. The problem with cisco and juniper intergration in MVPN only happens durinf the time of inter-as communication else it works fine.