Table Of Contents
Configuring Source Specific Multicast
This chapter describes how to configure Source Specific Multicast (SSM).
For a complete description of the SSM commands in this chapter, refer
to the "IP Multicast Routing Commands" chapter of the Cisco IOS IP Command Reference, Volume 3 of 3: Multicast.
To locate documentation of other commands that appear in this chapter,
use the command reference master index, or search online.
The Source Specific Multicast feature is an extension of IP multicast
where datagram traffic is forwarded to receivers from only those
multicast sources to which the receivers have explicitly joined. For
multicast groups configured for SSM, only source-specific multicast
distribution trees (no shared trees) are created.
To identify the hardware platform or software image information
associated with a feature, use the Feature Navigator on Cisco.com to
search for information about the feature or refer to the software
release notes for a specific release. For more information, see the
"Identifying Supported Platforms" section in the "Using Cisco IOS
Software" chapter.
SSM Components Overview
SSM is a datagram delivery model that best supports one-to-many
applications, also known as broadcast applications. SSM is a core
networking technology for the Cisco implementation of IP multicast
solutions targeted for audio and video broadcast application
environments. This chapter discusses the following Cisco IOS components
that support the implementation of SSM:
•
Protocol Independent Multicast source specific mode (PIM-SSM)
Protocol Independent Multicast source specific mode (PIM-SSM)
•Internet Group Management Protocol Version 3 (IGMPv3)
Internet Group Management Protocol Version 3 (IGMPv3)
•Internet Group Management Protocol Version 3 lite (IGMP v3lite)
Internet Group Management Protocol Version 3 lite (IGMP v3lite)
•URL Rendezvous Directory (URD)
URL Rendezvous Directory (URD)
PIM-SSM is the routing protocol that supports the implementation of SSM
and is derived from PIM sparse mode (PIM-SM). IGMP is the Internet
Engineering Task Force (IETF) standards track protocol used for hosts to
signal multicast group membership to routers. Version 3 of this
protocol supports source filtering, which is required for SSM. To run
SSM with IGMPv3, SSM must be supported in the Cisco IOS router, the host
where the application is running, and the application itself. IGMP
v3lite and URD are two Cisco-developed transition solutions that enable
the immediate development and deployment of SSM services, without the
need to wait for the availability of full IGMPv3 support in host
operating systems and SSM receiver applications. IGMP v3lite is a
solution for application developers that allows immediate development of
SSM receiver applications switching to IGMPv3 as soon as it becomes
available. URD is a solution for content providers and content
aggregators that enables them to deploy receiver applications that are
not yet SSM enabled (through support for IGMPv3). IGMPv3, IGMP v3lite,
and URD interoperate with each other, so that both IGMP v3lite and URD
can easily be used as transitional solutions toward full IGMPv3 support
in hosts.
How SSM Differs from Internet Standard Multicast
The current IP multicast infrastructure in the Internet and many
enterprise intranets is based on the PIM-SM protocol and Multicast
Source Discovery Protocol (MSDP). These protocols have proved to be
reliable, extensive, and efficient. However, they are bound to the
complexity and functionality limitations of the Internet Standard
Multicast (ISM) service model. For example, with ISM, the network must
maintain knowledge about which hosts in the network are actively sending
multicast traffic. With SSM, this information is provided by receivers
through the source addresses relayed to the last hop routers by IGMPv3,
IGMP v3lite, or URD. SSM is an incremental response to the issues
associated with ISM and is intended to coexist in the network with the
protocols developed for ISM. In general, SSM provides a more
advantageous IP multicast service for applications that utilize SSM.
ISM service is described in RFC 1112. This service consists of the
delivery of IP datagrams from any source to a group of receivers called
the multicast host group. The datagram traffic for the multicast host
group consists of datagrams with an arbitrary IP unicast source address S
and the multicast group address G as the IP destination address.
Systems will receive this traffic by becoming members of the host group.
Membership to a host group simply requires signalling the host group
through IGMP Version 1, 2, or 3.
In SSM, delivery of datagrams is based on (S, G) channels. Traffic for
one (S, G) channel consists of datagrams with an IP unicast source
address S and the multicast group address G as the IP destination
address. Systems will receive this traffic by becoming members of the
(S, G) channel. In both SSM and ISM, no signalling is required to become
a source. However, in SSM, receivers must subscribe or unsubscribe to
(S, G) channels to receive or not receive traffic from specific sources.
In other words, receivers can receive traffic only from (S, G) channels
to which they are subscribed, whereas in ISM, receivers need not know
the IP addresses of sources from which they receive their traffic. The
proposed standard approach for channel subscription signalling utilizes
IGMP INCLUDE mode membership reports, which are supported only in IGMP
Version 3.
SSM IP Address Range
SSM can coexist with the ISM service by applying the SSM delivery model
to a configured subset of the IP multicast group address range. The
Internet Assigned Numbers Authority (IANA) has reserved the address
range 232.0.0.0 through 232.255.255.255 for SSM applications and
protocols. Cisco IOS software allows SSM configuration for an arbitrary
subset of the IP multicast address range 224.0.0.0 through
239.255.255.255. When an SSM range is defined, existing IP multicast
receiver applications will not receive any traffic when they try to use
addresses in the SSM range (unless the application is modified to use
explicit (S, G) channel subscription or is SSM enabled through URD).
SSM Operations
An established network, in which IP multicast service is based on
PIM-SM, can support SSM services. SSM can also be deployed alone in a
network without the full range of protocols that are required for
interdomain PIM-SM (for example, MSDP, Auto-RP, or bootstrap router
[BSR]) if only SSM service is needed.
If SSM is deployed in a network already configured for PIM-SM (Cisco IOS
Release 12.0 or later releases is recommended), then only the last hop
routers must be upgraded to a Cisco IOS software image that supports
SSM. Routers that are not directly connected to receivers do not have to
upgrade to a Cisco IOS software image that supports SSM. In general,
these nonlast hop routers must only run PIM-SM in the SSM range, and may
need additional access control configuration to suppress MSDP
signalling, registering, or PIM-SM shared tree operations from occurring
within the SSM range.
The SSM mode of operation is enabled by configuring the SSM range through the ip pim ssm global configuration command. This configuration has the following effects:
•For
groups within the SSM range, (S, G) channel subscriptions are accepted
through IGMPv3 INCLUDE mode membership reports, IGMP v3lite, or URD
(each of these methods must be configured on a per-interface basis).
IGMP v3lite and URD (S, G) channel subscriptions are ignored for groups
outside the SSM range.
For
groups within the SSM range, (S, G) channel subscriptions are accepted
through IGMPv3 INCLUDE mode membership reports, IGMP v3lite, or URD
(each of these methods must be configured on a per-interface basis).
IGMP v3lite and URD (S, G) channel subscriptions are ignored for groups
outside the SSM range.
Both IGMP v3lite and URD are based on utilizing existing application
IGMP group membership and extending it with their respective (S, G)
channel subscription mechanism, which is ignored by Cisco IOS software
outside the SSM range of addresses. Within the SSM range, IGMP Version 1
(IGMPv1) or Version 2 (IGMPv2) group membership reports or IGMPv3
EXCLUDE mode membership reports are acted upon only in conjunction with
an (S, G) specific membership report from URD or IGMP v3lite.
•PIM
operations within the SSM range of addresses change to PIM-SSM, a mode
derived from PIM-SM. In this mode, only PIM (S, G) join and prune
messages are generated by the router, and no (S, G) rendezvous point
tree (RPT) or (*, G) RPT messages are generated. Incoming messages
related to RPT operations are ignored or rejected and incoming PIM
register messages are immediately answered with register-stop messages.
PIM-SSM is backward compatible with PIM-SM, unless a router is a last
hop router. Therefore, routers that are not last hop routers can run
PIM-SM for SSM groups (for example, if they do not yet support SSM).
PIM
operations within the SSM range of addresses change to PIM-SSM, a mode
derived from PIM-SM. In this mode, only PIM (S, G) join and prune
messages are generated by the router, and no (S, G) rendezvous point
tree (RPT) or (*, G) RPT messages are generated. Incoming messages
related to RPT operations are ignored or rejected and incoming PIM
register messages are immediately answered with register-stop messages.
PIM-SSM is backward compatible with PIM-SM, unless a router is a last
hop router. Therefore, routers that are not last hop routers can run
PIM-SM for SSM groups (for example, if they do not yet support SSM).
•No MSDP Source-Active (SA) messages within the SSM range will be accepted, generated, or forwarded.
No MSDP Source-Active (SA) messages within the SSM range will be accepted, generated, or forwarded.
IGMPv3 Host Signalling
IGMPv3 is the third version of the IETF standards track protocol in
which hosts signal membership to last hop routers of multicast groups.
IGMPv3 introduces the ability for hosts to signal group membership with
filtering capabilities with respect to sources. A host can either signal
that it wants to receive traffic from all sources sending to a group
except for some specific sources (called EXCLUDE mode), or that it wants
to receive traffic only from some specific sources sending to the group
(called INCLUDE mode).
IGMPv3 can operate with both ISM and SSM. In ISM, both EXCLUDE and
INCLUDE mode reports are applicable. In SSM, only INCLUDE mode reports
are accepted by the last hop router. EXCLUDE mode reports are ignored.
For more information on IGMPv3, see the "Configuring IP Multicast Routing" chapter in this document.
IGMP v3lite Host Signalling
IGMP v3lite is a Cisco-developed transitional solution for application
developers to immediately start programming SSM applications. It allows
you to write and run SSM applications on hosts that do not yet support
IGMPv3 in their operating system kernel.
Applications must be compiled with the Host Side IGMP Library (HSIL) for
IGMP v3lite. This software provides applications with a subset of the
IGMPv3 applications programming interface (API) that is required to
write SSM applications. HSIL was developed for Cisco by Talarian and is
available from the following web page:
http://www.talarianmulticast.com/cgi-bin/igmpdownld
One part of the HSIL is a client library linked to the SSM application.
It provides the SSM subset of the IGMPv3 API to the SSM application. If
possible, the library checks whether the operating system kernel
supports IGMPv3. If it does, then the API calls simply are passed
through to the kernel. If the kernel does not support IGMPv3, then the
library uses the IGMP v3lite mechanism.
When using the IGMP v3lite mechanism, the library tells the operating
system kernel to join to the whole multicast group, because joining to
the whole group is the only method for the application to receive
traffic for that multicast group (if the operating system kernel only
supports IGMPv1 or IGMPv2). In addition, the library signals the (S, G)
channel subscriptions to an IGMP v3lite server process, which is also
part of the HSIL. A server process is needed because multiple SSM
applications may be on the same host. This server process will then send
IGMP v3lite-specific (S, G) channel subscriptions to the last hop Cisco
IOS router, which needs to be enabled for IGMP v3lite. This Cisco IOS
router will then "see" both the IGMPv1 or IGMPv2 group membership report
from the operating system kernel and the (S, G) channel subscription
from the HSIL daemon. If the router sees both of these messages, it will
interpret them as an SSM (S, G) channel subscription and join to the
channel through PIM-SSM. We recommend referring to the documentation
accompanying the HSIL software for further information on how to utilize
IGMP v3lite with your application.
IGMP v3lite is supported by Cisco only through the API provided by the
HSIL, not as a function of the router independent of the HSIL. By
default, IGMP v3lite is disabled. When IGMP v3lite is configured through
the ip igmp v3lite interface configuration command on an interface, it will be active only for IP multicast addresses in the SSM range.
URD Host Signalling
URD is a Cisco-developed transitional solution that allows existing IP
multicast receiver applications to be used with SSM without the need to
modify the application and change or add any software on the receiver
host running the application. URD is a content provider solution in
which the receiver applications can be started or controlled through a
web browser.
URD operates by passing a special URL from the web browser to the last
hop router. This URL is called a URD intercept URL. A URD intercept URL
is encoded with the (S, G) channel subscription and has a format that
allows the last hop router to easily intercept it.
As soon as the last hop router intercepts both an (S, G) channel
subscription encoded in a URD intercept URL and sees an IGMP group
membership report for the same multicast group from the receiver
application, the last hop router will use PIM-SSM to join toward the (S,
G) channel as long as the application maintains the membership for the
multicast group G. The URD intercept URL is thus only needed initially
to provide the last hop router with the address of the sources to join
to.
A URD intercept URL has the following syntax:
http://webserver:465/path?group=group&source=source1&...source=sourceN&
The webserver string is the name or IP
address to which the URL is targeted. This target need not be the IP
address of an existing web server, except for situations where the web
server wants to recognize that the last hop router failed to support the
URD mechanism. The number 465 indicates the URD port. Port 465 is
reserved for Cisco by the IANA for the URD mechanism so that no other
applications can use this port.
When the browser of a host encounters a URD intercept URL, it will try
to open a TCP connection to the web server on port 465. If the last hop
router is enabled for URD on the interface where the router receives the
TCP packets from the host, it will intercept all packets for TCP
connections destined to port 465 independent of the actual destination
address of the TCP connection (independent of the address of the web
server). Once intercepted, the last hop router will "speak" a very
simple subset of HTTP on this TCP connection, emulating a web server.
The only HTTP request that the last hop router will understand and reply
to is the following GET request:
GET argument HTTP/1.0
argument = /path?group=group&source=source1&...source=sourceN&
When it receives a GET command, the router tries to parse the argument
according to this syntax to derive one or more (S, G) channel
memberships. The path string of the argument is anything up to, but not including, the first question mark, and is ignored. The group and source1 through sourceN
strings are the IP addresses or fully qualified domain names of the
channels for which this argument is a subscription request. If the
argument matches the syntax shown, the router interprets the argument to
be subscriptions for the channels (source1, group) through (sourceN, group).
The router will accept the channel subscriptions if the following conditions are met:
•The IP address of the multicast group is within the SSM range.
The IP address of the multicast group is within the SSM range.
•The IP address of the host that originated the TCP connection is directly connected to the router.
The IP address of the host that originated the TCP connection is directly connected to the router.
If the channel subscription is accepted, the router will respond to the TCP connection with the following HTML page format:
HTTP/1.1 200 OK
Server:cisco IOS
Content-Type:text/html
<html>
<body>
Retrieved URL string successfully
</body>
</html>
If an error condition occurs, the <body> part of the returned HTML
page will carry an appropriate error message. The HTML page is a
by-product of the URD mechanism. This returned text may, depending on
how the web pages carrying a URD intercept URL are designed, be
displayed to the user or be sized so that the actual returned HTML page
is invisible.
The primary effect of the URD mechanism is that the router will remember
received channel subscriptions and will match them against IGMP group
membership reports received by the host. The router will "remember" a
URD (S, G) channel subscription for up to 3 minutes without a matching
IGMP group membership report. As soon as the router sees that it has
received both an IGMP group membership report for a multicast group G
and a URD (S, G) channel subscription for the same group G, it will join
the (S, G) channel through PIM-SSM. The router will then continue to
join to the (S, G) channel based only on the presence of a continuing
IGMP membership from the host. Thus, one initial URD channel
subscription is all that is needed to be added through a web page to
enable SSM with URD.
If the last hop router from the receiver host is not enabled for URD,
then it will not intercept the HTTP connection toward the web server on
port 465. This situation will result in a TCP connection to port 465 on
the web server. If no further provisions on the web server are taken,
then the user may see a notice (for example, "Connection refused") in
the area of the web page reserved for displaying the URD intercept URL
(if the web page was designed to show this output). It is also possible
to let the web server "listen" to requests on port 465 and install a
Common Gateway Interface (CGI) script that would allow the web server to
know if a channel subscription failed (for example, to subsequently
return more complex error descriptions to the user).
Because the router returns a Content-Type of text and HTML, the best way
to include the URD intercept URL into a web page is to use a frame. By
defining the size of the frame, you can also hide the URD intercept URL
on the displayed page.
By default, URD is disabled on all interfaces. When URD is configured through the ip urd interface configuration command on an interface, it will be active only for IP multicast addresses in the SSM range.
Benefits
IP Multicast Address Management Not Required
In the ISM service, applications must acquire a unique IP multicast
group address because traffic distribution is based only on the IP
multicast group address used. If two applications with different sources
and receivers use the same IP multicast group address, then receivers
of both applications will receive traffic from the senders of both
applications. Even though the receivers, if programmed appropriately,
can filter out the unwanted traffic, this situation would cause
generally unacceptable levels of unwanted traffic.
Allocating a unique IP multicast group address for an application is
still a problem. Most short-lived applications use mechanisms like
Session Description Protocol (SDP) and Session Announcement Protocol
(SAP) to get a random address, a solution that does not work well with a
rising number of applications in the Internet. The best current
solution for long-lived applications is described in RFC 2770, but this
solution suffers from the restriction that each autonomous system is
limited to only 255 usable IP multicast addresses.
In SSM, traffic from each source is forwarded between routers in the
network independent of traffic from other sources. Thus different
sources can reuse multicast group addresses in the SSM range.
Denial of Service Attacks from Unwanted Sources Inhibited
In SSM, multicast traffic from each individual source will be
transported across the network only if it was requested (through IGMPv3,
IGMP v3lite, or URD memberships) from a receiver. In contrast, ISM
forwards traffic from any active source sending to a multicast group to
all receivers requesting that multicast group. In Internet broadcast
applications, this ISM behavior is highly undesirable because it allows
unwanted sources to easily disturb the actual Internet broadcast source
by simply sending traffic to the same multicast group. This situation
depletes bandwidth at the receiver side with unwanted traffic and thus
disrupts the undisturbed reception of the Internet broadcast. In SSM,
this type of denial of service (DoS) attack cannot be made by simply
sending traffic to a multicast group.
Easy to Install and Manage
SSM is easy to install and provision in a network because it does not
require the network to maintain which active sources are sending to
multicast groups. This requirement exists in ISM (with IGMPv1, IGMPv2,
or IGMPv3).
The current standard solutions for ISM service are PIM-SM and MSDP.
Rendezvous point (RP) management in PIM-SM (including the necessity for
Auto-RP or BSR) and MSDP is required only for the network to learn about
active sources. This management is not necessary in SSM, which makes
SSM easier than ISM to install and manage, and therefore easier than ISM
to operationally scale in deployment. Another factor that contributes
to the ease of installation of SSM is the fact that it can leverage
preexisting PIM-SM networks and requires only the upgrade of last hop
routers to support IGMPv3, IGMP v3lite, or URD.
Ideal for Internet Broadcast Applications
The three benefits previously described make SSM ideal for Internet broadcast-style applications for the following reasons:
•The
ability to provide Internet broadcast services through SSM without the
need for unique IP multicast addresses allows content providers to
easily offer their service (IP multicast address allocation has been a
serious problem for content providers in the past).
The
ability to provide Internet broadcast services through SSM without the
need for unique IP multicast addresses allows content providers to
easily offer their service (IP multicast address allocation has been a
serious problem for content providers in the past).
•The
prevention against DoS attacks is an important factor for Internet
broadcast services because, with their exposure to a large number of
receivers, they are the most common targets for such attacks.
The
prevention against DoS attacks is an important factor for Internet
broadcast services because, with their exposure to a large number of
receivers, they are the most common targets for such attacks.
•The
ease of installation and operation of SSM makes it ideal for network
operators, especially in those cases where content needs to be forwarded
between multiple independent PIM domains (because there is no need to
manage MSDP for SSM between PIM domains).
The
ease of installation and operation of SSM makes it ideal for network
operators, especially in those cases where content needs to be forwarded
between multiple independent PIM domains (because there is no need to
manage MSDP for SSM between PIM domains).
Restrictions
Legacy Applications Within the SSM Range Restrictions
Existing applications in a network predating SSM will not work within
the SSM range unless they are modified to support (S, G) channel
subscriptions or are enabled through URD. Therefore, enabling SSM in a
network may cause problems for existing applications if they use
addresses within the designated SSM range.
IGMP v3lite and URD Require a Cisco IOS Last Hop Router
SSM and IGMPv3 are solutions that are being standardized in the IETF.
However, IGMP v3lite and URD are Cisco-developed solutions. For IGMP
v3lite and URD to operate properly for a host, the last hop router
toward that host must be a Cisco IOS router with IGMP v3lite or URD
enabled.
Note This
limitation does not apply to an application using the HSIL if the host
has kernel support for IGMPv3, because then the HSIL will use the kernel
IGMPv3 instead of IGMP v3lite.
This
limitation does not apply to an application using the HSIL if the host
has kernel support for IGMPv3, because then the HSIL will use the kernel
IGMPv3 instead of IGMP v3lite.
Address Management Restrictions
Address management is still necessary to some degree when SSM is used
with Layer 2 switching mechanisms. Cisco Group Management Protocol
(CGMP), IGMP snooping, or Router-Port Group Management Protocol (RGMP)
currently support only group-specific filtering, not (S, G)
channel-specific filtering. If different receivers in a switched network
request different (S, G) channels sharing the same group, then they
will not benefit from these existing mechanisms. Instead, both receivers
will receive all (S, G) channel traffic (and filter out the unwanted
traffic on input). Because of the ability of SSM to reuse the group
addresses in the SSM range for many independent applications, this
situation can lead to less than expected traffic filtering in a switched
network. For this reason it is important to follow the recommendations
set forth in the IETF drafts for SSM to use random IP addresses out of
the SSM range for an application to minimize the chance for reuse of a
single address within the SSM range between different applications. For
example, an application service providing a set of television channels
should, even with SSM, use a different group for each television (S, G)
channel. This setup will guarantee that multiple receivers to different
channels within the same application service will never experience
traffic aliasing in networks that include Layer 2 switches.
IGMP Snooping and CGMP Limitations
IGMPv3 uses new membership report messages that may not be recognized
correctly by older IGMP Snooping switches, in which case hosts will not
properly receive traffic. This situation is not an issue if URD or IGMP
v3lite is used with hosts where the operating system is not upgraded for
IGMPv3, because IGMP v3lite and URD rely only on IGMPv1 or IGMPv2
membership reports. For more information about switching issues related
to IGMP (especially with CGMP), refer to the "Configuring IGMP Version
3" section of the "Configuring IP Multicast Routing" chapter in this
document.
URD Intercept URL Limitations
A URD intercept URL string must be fewer than 256 bytes in length, starting from the /path
argument. In the HTTP/TCP connection, this string must also be
contained within a single TCP/IP packet. For example, for a 256-byte
string, a link maximum transmission unit (MTU) of 128 bytes between the
host and intercepting router would cause incorrect operation of URD.
State Maintenance Limitations
In PIM-SSM, the last hop router will continue to periodically send (S,
G) join messages if appropriate (S, G) subscriptions are on the
interfaces. Therefore, as long as receivers send (S, G) subscriptions,
the shortest path tree (SPT) state from the receivers to the source will
be maintained, even if the source is not sending traffic for longer
periods of time (or even never).
This case is opposite to PIM-SM, where (S, G) state is maintained only
if the source is sending traffic and receivers are joining the group. If
a source stops sending traffic for more than 3 minutes in PIM-SM, the
(S, G) state will be deleted and only reestablished after packets from
the source arrive again through the RPT. Because no mechanism in PIM-SSM
notifies a receiver that a source is active, the network must maintain
the (S, G) state in PIM-SSM as long as receivers are requesting receipt
of that channel.
HSIL Limitations
As explained in the "IGMP v3lite Host Signalling"
section, the HSIL tries to determine if the host operating system
supports IGMPv3. This check is made so that a single application can be
used both on hosts where the operating system has been upgraded to
IGMPv3 and on hosts where the operating system only supports IGMPv1 or
IGMPv2. Checking for the availability of IGMPv3 in the host operating
system can only be made by the HSIL if IGMPv3 kernel support exists for
at least one version of this operating system at the time when the HSIL
was provided. If such an IGMPv3 kernel implementation has become
available only recently, then users may need to also upgrade the HSIL on
their hosts so that applications compiled with the HSIL will then
dynamically bind to the newest version of the HSIL, which should support
the check for IGMPv3 in the operating system kernel. Upgrading the HSIL
can be done independently of upgrading the application itself.
SSM Configuration Task List
To configure SSM, perform the tasks described in the following sections.
The tasks in the first section are required; the tasks in the remaining
section are optional.
•Configuring SSM (Required)
Configuring SSM (Required)
•Monitoring SSM (Optional)
Monitoring SSM (Optional)
Configuring SSM
To configure SSM, use the following commands beginning in global configuration mode:
Monitoring SSM
To monitor SSM, use the following commands in privileged EXEC mode, as needed:
SSM Configuration Examples
This section provides the following SSM configuration examples:
SSM with IGMPv3 Example
The following example shows how to configure a router (running IGMPv3) for SSM:
ip multicast-routing
!
interface Ethernet3/1
ip address 172.21.200.203 255.255.255.0
description backbone interface
ip pim sparse-dense-mode
!
interface Ethernet3/2
ip address 131.108.1.2 255.255.255.0
ip pim sparse-dense-mode
description ethernet connected to hosts
ip igmp version 3
!
ip pim ssm default
SSM with IGMP v3lite and URD Example
The following example shows how to configure IGMP v3lite and URD on
interfaces connected to hosts for SSM. Configuring IGMP v3lite and URD
is not required or recommended on backbone interfaces.
interface ethernet 3/1
ip address 172.21.200.203 255.255.255.0
ip pim sparse-dense-mode
description ethernet connected to hosts
!
interface ethernet 1
description ethernet connected to hosts
ip address 131.108.1.2 255.255.255.0
ip pim sparse-dense-mode
ip urd
ip igmp v3lite
SSM Filtering Example
The following example shows how to configure filtering on a legacy RP
router running Cisco IOS releases earlier than Release 12.1(3)T for SSM
routing. This filtering will suppress all unwanted PIM-SM and MSDP
traffic in the SSM range. Without this filtering, SSM will still
operate, but there may be additional RPT traffic if legacy first hop and
last hop routers exist in the network.
ip access-list extended no-ssm-range
deny ip any 232.0.0.0 0.255.255.255 ! SSM range
permit ip any any
! Deny registering in SSM range
ip pim accept-register list no-ssm-range
ip access-list extended msdp-nono-list
deny ip any 232.0.0.0 0.255.255.255 ! SSM Range
! .
! .
! .
! See ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt
for other SA
! messages that typically need to be filtered.
permit ip any any
! Filter generated SA messages in SSM range. This configuration is only needed
if there
! are directly connected sources to this router. The "ip pim accept-register"
command
! filters remote sources.
ip msdp redistribute list msdp-nono-list
! Filter received SA messages in SSM range. "Filtered on receipt" means messages
are
! neither processed or forwarded. Needs to be configured for each MSDP peer.
ip msdp sa-filter in msdp-peer1 list msdp-nono-list
! .
! .
! .
ip msdp sa-filter in msdp-peerN list msdp-nono-list
