Enabling IP Multicast with Internet2

Scope: Note that this isn'tabout multicast in general, but aimed narrowlyat what a participant site has to do on a Cisco or Juniper router toconnect to Internet2.It assumes basic familiarity with multicast concepts. For moreinformation about multicast in general, multicast protocols mentionedhere, and for further help or information, including some excellent troubleshooting and debugging documents, see the "For Further Information"section at the end of this document.

There are three parts to a "native multicast" peering arrangement with Internet2: MBGP, PIM-SparseMode, and MSDP. This short document describeshow to enable each and a few things to look for to determine whether they'reworking at all. It doesn't discuss debugging or troubleshooting strategies,which is another subject not widely understood and very much needed.  Configuration examples are available here for Cisco (MBGP, PIM, and MSDP) or Juniper (MBGP, PIM, and MSDP).

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Cisco configuration:

Global commands

There is one global router command just to enable multicast:

  ip multicast-routing

The configurations below represent what a peer might minimally do to enablemulticast peering with Internet2. For these examples, we'll assume a neighborwith address 5.5.5.5 in AS 555:

                 Neighbor      Abilene router
IP addresses    5.5.5.5/30      5.5.5.6/30
AS number       555             11537

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MBGP for Cisco

Enable MBGP:

• Within 'router BGP' context, change your network and neighborstatements  from implicit unicast-only to unicast and multicast. Include the nlri unicast multicast phrase for each networkand neighbor with whom you want both types of BGP negotiation:
  
  • pre-12.1:

    change from:
  
    network 5.5.5.0
    neighbor 5.5.5.6 remote-as 11537
  
    to:
  
    network 5.5.5.0 nlri unicast multicast
    neighbor 5.5.5.6 remote-as 11537 nlri unicast multicast

  • 12.1 and later:

    change from:
  
    network 5.5.5.0
    neighbor 5.5.5.6 remote-as 11537
  
    to:
  
    neighbor 5.5.5.6 remote-as 11537
    address-family ipv4 unicast
      neighbor 5.5.5.6 activate
    neighbor 5.5.5.6 remote-as 11537
    address-family ipv4 multicast
      neighbor 5.5.5.6 activate

• To verify that MBGP is talking for both unicast and multicast, see output from "show ip mbgpsum" (look for state/prefixes) and/or "show ip bgp neighbor 5.5.5.5",looking for lines like these (this is for 12.0, but 12.1 will have similarindications):

&; Neighbor NLRI negotiation:
    Configured for unicast and multicast routes
    Peer negotiated unicast and multicast routes
    Exchanging unicast and multicast routes

and:

  Number of unicast/multicast prefixes received 3/3

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PIM for Cisco

• Enable PIM on the point-to-point interface and add multicast- boundaryadministrative scoping:

interface ATMx/y.1 point-to-point
 description to I2/Abilene,AS11537,
     contact noc@abilene.iu.edu,317-278-6622

 ip address 5.5.5.5 255.255.255.252
 ip pim sparse-mode
 ip multicast boundary multicast-boundary

• This is the multicast-boundary list we presently use in Internet2, and therehave been some suggestions for additional values for which we're solicitingfeedback/consensus from the I2 community. The expressions below block sendingRP announce and discovery packets and set the accepted administrative scopingto block 'local' multicast.

ip access-list standard multicast-boundary
 deny   224.0.1.39
 deny   224.0.1.40
 deny   239.0.0.0 0.255.255.255
 permit any

• If PIM is configured on both sides of the connection, then each shouldsee the other as a "PIM neighbor", e.g.:

abilene-gsr>sho ip pim interface

Address      Interface        Version/Mode    Nbr   Query     DR
                                              Count Intvl
5.5.5.6      POS0/0           v2/Sparse        1    30     0.0.0.0
1.1.1.1      ATM1/0.1         v2/Sparse       *0    30     0.0.0.0

First of all, if you have PIM enabled for an interface it will appearin this list, so that's a good first sanity check that you've turned iton at all. Note that the "Mode" column indicates v2/Sparse,which are both good. In the column "Nbr count", look for non-zeroneighbor counts: 0 means that no neighbor negotiation has occured(there is no PIM neighbor there; PIM is not turned on at your neighbor'sside of the connection), while 1 means PIM *is* on at your neighbor'sside of the connection.

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MSDP for Cisco

• Finally, enable MSDP to your peer's RP. USUALLY (and this is the Internet2 preference),the MSDP peer address is the other end of the point-to-pointconnection. This will be the address to be used for Internet2. Some sitesprefer to use a loopback address for their MSDP peer address, inwhich case they must also indicate to MSDP to use that interface. (theaddress in the 'peer' and the 'sa-filter' statements are the same, andare the address of your MSDP peer, usually the same as the MBGP peer.)
  • (alternatively, if you're using e.g. a loopback address for
    your MSDP source:)

 ip msdp peer 5.5.5.6
 ip msdp sa-filter out 5.5.5.6 list 111

 ip msdp peer 5.5.5.6 connect-source Loopback0
 ip msdp sa-filter out 5.5.5.6 list 111

• Also, it's a good idea to have a MSDP filter applied to theconnection,to keep the peer from sending improper source-activeannouncements. You may also implement SA-count limits to keep the neighbor fromflooding you with advertisements.   This list is referred to by the "ip msdp sa-filter ... list 111" command above; the list of prefixes Internet2 blocks are listed elsewhere in this document, but this is the syntax:

 access-list 111 deny   ip any host 224.0.1.2
 access-list 111 deny   ip any host 224.0.1.3

           ... etc ...

           (add the rest of the list of prefixes below and remember to add these RFC1918 addresses:)

 access-list 111 deny   ip 10.0.0.0 0.255.255.255 any
 access-list 111 deny   ip 127.0.0.0 0.255.255.255 any
 access-list 111 deny   ip 172.16.0.0 0.15.255.255 any
 access-list 111 deny   ip 192.168.0.0 0.0.255.255 any
 access-list 111 permit ip any any

• To see if the MSDP peering is working bidirectionally, "show ip msdpsum" and look for a state of "up". If they're joined to multicaststhrough this path, you should see SAs (source advertisements) from theirAS in "show ip msdp count".

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Juniper router configuration:

Global considerations

No global router commands to enable multicast are necessary, howeveryour router may need a tunnel PIC in order to do multicast (if it isacting as an RP or will have directly-connected multicast sources.)Some routers, for instance the 7i or J series, have them built in ordon't need them.

The configurations below represent what an Internet2 peer must minimally do to enablemulticast peering with Internet2. For these examples, we'll assume a neighborwith address 5.5.5.5 in AS 555, and the Internet2 router's address for that connection is 5.5.5.6.  Abilene's AS is 11537.

                 Neighbor      Abilene router
IP addresses    5.5.5.5/30      5.5.5.6/30
AS number       555             11537

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MBGP for Juniper

JunOS assumes both unicast and multicast for ipv4 BGP peering, so if aBGP neighbor is configured, the Juniper will try to negotiate bothunicast and multicast NLRI and will settle on whatever the partner iswilling to do.  So if you want to do both unicast and multicastpeering with the Internet2 router, the configuration is simply:

protocols {
   bgp {
      group Abilene {
          neighbor 5.5.5.6 {
              family inet {
                   any;    (this does unicast and multicast;

                                     alternatively, you could specify only "multicast")
              }
              type external;
              description "Abilene";
              peer-as 11537;
          }

PIM for Juniper

• Enable PIM on the point-to-point interface toward Internet2 and specify the RP:

protocols {
   pim {
      rp {		(use this to specify your RP)
          static {	(if RP is elsewhere. "local" if it is this router)
             family inet {
                 address <address of your RP here>;
                 group-ranges {
                     224.0.0.0/4;
                 }
             }
          }
      interface so-0/0/0 {	("all" also works if you want PIM everywhere. 
                                                          This is the interface facing Abilene)
           mode sparse;
           version 2;
           } 

• If PIM is working on both sides of the connection, then each shouldsee the other as a "PIM neighbor", e.g.:

juniper>sho pim interface
Name                   Stat Mode       IP V State Count DR address
so-0/0/0.0             Up   Sparse      4 2 P2P       1 

First of all, if you have PIM enabled for an interface it will appearin this list, so that's a good first sanity check that you've turned iton at all. "Stat(us)" shows "up", which is what you're looking for. Note that the "V(ersion)" and "Mode" columns indicate 2 and Sparse,which should both be configured. In the column "Count", look for non-zeroneighbor counts: 0 means that no neighbor negotiation has occured(there is no PIM neighbor there; PIM is not turned on at your neighbor'sside of the connection), while 1 means PIM *is* working from your neighbor'sside of the connection to you.  A DR ("designated router") isn't needed for a point-to-point connection.

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MSDP for Juniper

• Finally,enable MSDP to your peer's RP. USUALLY (and this is the Internet2preference),the MSDP peer address is the other end of the point-to-point connectionThis will be the address to be used for Internet2. Some sitesprefer to use a loopback address for their MSDP peering address, inwhich case they must also indicate to MSDP to use that interface. (theaddress in the 'peer' and the 'sa-filter' statements are the same, andare the address of your MSDP peer, usually the same as the MBGP peer.)
• Also, it's a good idea to have a MSDP filter applied to theconnection, to keep the peer from sending improper source-activeannouncements.  You may also implement SA-count limits to keep theneighbor from flooding you with advertisements.

 protocols {
    msdp {
      group Abilene {
         export MSDP-FILTER;
         import MSDP-FILTER;
         peer 5.5.5.6 {
 local-address 5.5.5.5;  
(you could use your loopback address here if you need to)
         }
...
 policy-options {
    policy-statement MSDP-FILTER {
        term bad-groups {
            from {
                route-filter 224.0.1.2/32 exact;
(etc...  the content of MSDP-FILTER is listed separately in this document)
            }
            then reject;
        }
        term bad-sources {
            from {
                source-address-filter 10.0.0.0/8 orlonger;
                source-address-filter 127.0.0.0/8 orlonger;
                source-address-filter 172.16.0.0/12 orlonger;
                source-address-filter 192.168.0.0/16 orlonger;
            }
            then reject;
        }
        term allow {
            then accept;
        }
    }

• You can verify that MSDP peering is up with the "show msdp brief" command. Look for "State: Established".

juniper> show msdp brief   
Peer address Local address State   Last up/down Peer-Group SA Count
5.5.5.6      5.5.5.5       Established  3w1d18h Abilene    1038/2101

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MSDP Filter contents

It's a good idea to limit the source-active advertisements your peercan send to you to legitimate multicast group addresses.  This canbe done on both Cisco and Juniper platforms with filters applied toyour MSDP peers, as shown above.  Internet2's current MSDP filterblocks the prefixes listed below.  Its contents have input fromthe Internet2 Multicast Working Group, the Internet Assigned NumbersAuthority (IANA) official list of multicast networks, and recommendations in www.cisco.com/warp/customer/105/49.html and draft-nickless-ipv4-mcast-unusable-03 (December 2003).
This version of the list uses Juniper syntax; Cisco's is "access-list111 deny ip any host 224.0.2.2" for /32s or "deny ip any 224.77.0.00.0.255.255" for networks, etc. for this same set of prefixes).

   route-filter 224.0.1.2/32 exact;	! SGI-DOGFIGHT
   route-filter 224.0.1.3/32 exact;     ! RWHOD
   route-filter 224.0.1.8/32 exact;     ! SUB-NIS
   route-filter 224.0.1.22/32 exact;    ! SRVLOC
   route-filter 224.0.1.24/32 exact;    ! MICROSOFT-DS--WINS locator service
   route-filter 224.0.1.25/32 exact;    ! NBC-PRO
   route-filter 224.0.1.35/32 exact;    ! SRVLOC-DA
   route-filter 224.0.1.39/32 exact;    ! AUTORP-ANNOUNCE
   route-filter 224.0.1.40/32 exact;    ! AUTORP-DISCOVERY
   route-filter 224.0.1.60/32 exact;    ! HP-DEVICE-DISC
   route-filter 224.0.2.1/32 exact;     ! HP-DEVICE-DISC
   route-filter 224.0.2.2/32 exact;     ! SUN-RPC
   route-filter 224.77.0.0/16 orlonger;	! NORTON GHOST
   route-filter 225.1.2.3/32 exact;     ! ALTIRIS
   route-filter 226.77.0.0/16 orlonger;     ! NORTON GHOST
   route-filter 229.55.150.208/32 exact;     ! NORTON GHOST
   route-filter 234.42.42.40/30 orlonger;     ! IMAGECAST
   route-filter 234.142.142.42/31 orlonger;     ! IMAGECAST
   route-filter 234.142.142.44/30 orlonger;     ! IMAGECAST
   route-filter 234.142.142.48/28 orlonger;     ! IMAGECAST
   route-filter 234.142.142.64/26 orlonger;     ! IMAGECAST
   route-filter 234.142.142.128/29 orlonger;    ! IMAGECAST
   route-filter 234.142.142.136/30 orlonger;    ! IMAGECAST
   route-filter 234.142.142.140/31 orlonger;    ! IMAGECAST
   route-filter 234.142.142.142/32 exact;     ! IMAGECAST
   route-filter 232.0.0.0/8 orlonger;   ! SSM range--should be no MSDP here
   route-filter 239.0.0.0/8 orlonger;   ! admin scoped

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For Further Information:

1. Cisco web pages: ftp://ftpeng.cisco.com/ipmulticast/index.htmlincluding recommended releases, tutorials, sample configurations, and muchmore.
2. Internet2 Multicast working group: multicast.internet2.edu, including references, debugging tutorial, and contents of I2 hands-on multicast workshops.
3. NCNE web pages: www.ncne.org/documentation/faq/multicast.html including FAQs and many tutorials from users and vendors.
4. NCNE multicast introduction at I2 member meeting Spring 2000: www.internet2.edu/presentations/200003228-I2MM-Goodwin.htm
5. NCNE user help: NCNE, the National Center for Network Engineering at PittsburgSupercomputer Center, has agreed to provide personal help to sites bringingup or having troubles with multicast. Write to ncne@ncne.organdask for help specifically with Multicast. Indicate that you're an Internet2site.
6. "Best current practices for enabling Multicast networks": a presentation by Bill Nickless at the February 2003 Joint Techs workshop.
7. "Protecting multicast-enabled networks": a presentation by Matt Davy at the July 2004 Joint Techs workshop.
8. IPv4 Multicast Unusable Group and Source Addresses, version 3 of a draft by Bill Nickless (Dec 2003).
9. Multicast troubleshooting methodology: Bill Nickless presentation. This version is from 2003.
10. Multicast troubleshooting: UCSB guide
11. Multicast troubleshooting: presentation given at Multicast workshop held in Vancouver, Canada, May 2004.
12. Triumf AG Multicast references: several good, current (2004), multicast references.
13. Internet Assigned Numbers Authority (IANA) official list of multicast networks.
14. A book, Interdomain MulticastRouting: Practical Juniper Networks and Cisco Systems Solutions (2002), available here at Amazon.
15. A book, Developing IP Multicast Networks: The Definitive Guide to Designing and Deploying Cisco Multicast Networks (2000), available here at Amazon.