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HP 5500 Ei 5500 Si Switch Series Configuration Guide

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    							 85 
 system-view 
[SwitchC] multicast routing-enable 
[SwitchC] interface vlan-interface 100 
[SwitchC-Vlan-interface100] igmp enable 
[SwitchC-Vlan-interface100] pim dm 
[SwitchC-Vlan-interface100] quit 
[SwitchC] interface vlan-interface 101 
[SwitchC-Vlan-interface101] pim dm 
[SwitchC-Vlan-interface101] quit 
# Enable IP multicast routing on Switch A and enable PIM-DM on each interface. 
 system-view 
[SwitchA] multicast routing-enable 
[SwitchA] interface vlan-interface 300 
[SwitchA-Vlan-interface300] pim dm 
[SwitchA-Vlan-interface300] quit 
[SwitchA] interface vlan-interface 102 
[SwitchA-Vlan-interface102] pim dm 
[SwitchA-Vlan-interface102] quit 
The configuration on Switch B is similar to  that on Switch A. (Details not shown.)  
# Use the display multicast rpf-info  command to view the RPF routes to Source 2 on Switch B and 
Switch C.  
[SwitchB] display multicast rpf-info 50.1.1.100 
[SwitchC] display multicast rpf-info 50.1.1.100 
N o  i n f o r m a t i o n  i s  d i s p l a y e d .  T h i s  m e a n s  t h a t  n o  R P F  r o u t e  t o  S o u r c e  2  e x i s t s  o n  S w i t c h  B  o r  S w i t c h  
C.  
3.  Configure a static multicast route: 
# Configure a static multicast route on Switch B, specifying Switch A as its RPF neighbor on the 
route to Source 2.  
[SwitchB] ip rpf-route-static 50.1.1.100 24 30.1.1.2 
# Configure a static multicast route on Switch C, specifying Switch B as its RPF neighbor on the 
route to Source 2.  
[SwitchC] ip rpf-route-static 10.1.1.100 24 20.1.1.2 
4. Verify the configuration: 
# Use the display multicast rpf-info  command to view the RPF routes to Source 2 on Switch B and 
Switch C. 
[SwitchB] display multicast rpf-info 50.1.1.100 
 RPF information about source 50.1.1.100: 
     RPF interface: Vlan-interface102, RPF neighbor: 30.1.1.2 
     Referenced route/mask: 50.1.1.0/24 
     Referenced route type: static multicast 
     Route selection rule: preference-preferred 
     Load splitting rule: disable 
[SwitchC] display multicast rpf-info 50.1.1.100 
 RPF information about source 50.1.1.100: 
     RPF interface: Vlan-interface101, RPF neighbor: 20.1.1.2 
     Referenced route/mask: 50.1.1.0/24 
     Referenced route type: static multicast
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     Route selection rule: preference-preferred 
     Load splitting rule: disable 
The output shows that the RPF routes to Source 2 exist on Switch B and Switch C. The routes are the 
configured static routes.  
Troubleshooting multicast routing and forwarding  
Static multicast route failure 
Symptom 
No dynamic routing protocol is enabled on the routers,  and the physical status and link layer status of 
interfaces are both up, but the static multicast route fails. 
Analysis 
•   If the static multicast route is not configured  or updated correctly to match the current network 
conditions, the route entry and the configuration information of static multicast route do not exist in 
the multicast routing table. 
•   If a better route is found, the stat ic multicast route might also fail. 
Solution 
1. Use the  display multicast routing-table static  command to view the information of static multicast 
routes to verify that the static multicast route ha s been correctly configured and that the route entry 
exists in the multicast routing table. 
2.  Check the type of the next hop interface of the st atic multicast route. If the interface is not a 
point-to-point interface, be sure to specify th e next hop address for the outgoing interface when 
you configure the static multicast route. 
3.  Check that the static multicast route matches the specified routing protocol. If a protocol was 
specified in static multicast route configuration, enter the  display ip routing-table command to 
check if an identical route was added by the protocol. 
4.  Check that the static multicast route matches the  specified routing policy. If a routing policy was 
specified when the static multicast route was configured, enter the  display route-policy command 
to check the configured routing policy. 
Multicast data fails to reach receivers 
Symptom 
The multicast data can reach some routers but fails to reach the last-hop router. 
Analysis 
If a multicast forwarding boundary has been configured through the  multicast boundary command, any 
multicast packet will be kept from crossing the boundary. 
Solution 
1.  Use the  display pim routing-table  command to verify that the corresponding (S, G) entries exist on 
the router. If yes, the router has received the mult icast data. Otherwise, the router has not received 
the data.
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    							 87 
2.
 
Use the  display multicast boundary  command to check the multicast boundary information on the 
interfaces. Use the multicast boundary  command to change the multicast forwarding boundary 
setting. 
3.  In the case of PIM-SM, use the  display current-configuration command to check the BSR and RP 
information.
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Configuring IGMP (available only on the HP 
5500 EI) 
Overview 
As a TCP/IP protocol responsible for IP multicast group member management, the Internet Group 
Management Protocol (IGMP) is used by IP hosts an d adjacent multicast routers to establish and maintain 
their multicast group memberships.  
The term router in this document refers to both routers and Layer 3 switches. 
The term interface in the IGMP features refers to Layer 3 interfaces, including VLAN interfaces and 
route-mode (or Layer 3) Ethernet ports. You can set an  Ethernet port to operate in route mode by using the 
port  link-mode  route  command (see  Layer 2—LAN Switching Configuration Guide ). 
IGMP versions  
•  IGMPv1 (defined in RFC 1 112 )  
•   IGMPv2 (defined in RFC 2236) 
•   IGMPv3 (defined in RFC 3376) 
All IGMP versions support the Any-Source Multicast (ASM) model. In addition to the ASM model, 
IGMPv3 can directly implement the Source-Specific Multicast (SSM) model. IGMPv1 and IGMPv2 must 
work with the IGMP SSM mapping function to implement the SSM model.  
For more information about the ASM and SSM models, see  Multicast overview. 
Introduction to IGMPv1 
IGMPv1 manages multicast group memberships mainly based on the query and response mechanism.  
All multicast routers on the same subnet ca n receive IGMP membership report messages —often called 
reports — from hosts, but the subnet needs only one router for sending IGMP query messages —often 
called queries.  The querier election mechanism determines which router acts as the IGMP querier on 
the subnet.
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In IGMPv1, the designated router (DR) elected by the working multicast routing protocol (such as PIM) 
serves as the IGMP querier.  
For more information about DR, see  Configuring PIM (available only on the HP 5500 EI)   
Figure 31  IGMP queries and reports 

 
 
 
Assume that Host B and Host C are interested in multicast data addressed to multicast group G1, and 
Host A is interested in multicas t data addressed to G2, as shown in  Figure 31. T
he following process 
describes how the hosts join the multicast groups and how the IGMP querier (Router B in the figure) 
maintains the multicast group memberships:  
1.  The hosts send unsolicited IGMP reports to the addres ses of the multicast groups that they want to 
join, without having to wait for the IG MP queries from the IGMP querier.  
2. The IGMP querier periodically mu lticasts IGMP queries (with the destination address of 224.0.0.1) 
to all hosts and routers on the local subnet.  
3.  After receiving a query message, Host B or Host C  (the delay timer of whichever expires first) sends 
an IGMP report to the multicast group address of  G1, to announce its membership for G1. Assume 
that Host B sends the report message. After receivin g the report from Host B, Host C (which is on 
the same subnet as Host B) suppresses its own report for G1, because the IGMP routers (Router A 
and Router B) have already known that at least one ho st on the local subnet is interested in G1. This 
IGMP report suppression mechanism helps  reduce traffic on the local subnet.  
4. At the same time, because Host A is interested  in G2, it sends a report to the multicast group 
address of G2.  
5.  Through the query/report process, the IGMP routers determine that members of G1 and G2 are 
attached to the local subnet, and  the multicast routing protocol that is running on the routers (PIM, 
for example) generates (*, G1) and (*, G2) multicas t forwarding entries. These entries will be the 
basis for subsequent multicast forwarding, wher e asterisk represents any multicast source.  
6. When the multicast data addressed to G1 or G2 re aches an IGMP router, because the (*, G1) and 
(*, G2) multicast forwarding entries exist on the IGMP router, the router forwards the multicast 
data to the local subnet, and then the receivers on the subnet receive the data.  
IGMPv1 does not specifically define a leave group message (often called a leave message). When an 
IGMPv1 host is leaving a multicast group, it stops sending reports to the address of the multicast group 
Query
Report
DR
Host A (G2) Host B
(G1) Host C
(G1)
Ethernet Router A
Router B
IP network
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    							 90 
that i t l istene d to. I f  no  member  exists  i n a mu l tic ast g roup on the  subnet, the  I GM P  router  wi l l  not re c eive 
any report addressed to that multicast group. In this  case, the router will delete the multicast forwarding 
entries for that multicast group after a period of time.  
Enhancements in IGMPv2 
Compared with IGMPv1, IGMPv2 has introduced a querier election mechanism and a leave-group 
mechanism.  
Querier election mechanism  
In IGMPv1, the DR elected by the Layer 3 multicast routing protocol (such as PIM) serves as the querier 
among multiple routers on the same subnet.  
IGMPv2 introduced an independent querier election mechanism. The querier election process is as 
follows:  
1.  Initially, every IGMPv2 router assumes itself  as the querier and sends IGMP general query 
messages (often called general queries) to  all hosts and routers on the local subnet. The 
destination address is 224.0.0.1.  
2.  After receiving a general query,  every IGMPv2 router compares th e source IP address of the query 
message with its own interface address. After comparison, the router with the lowest IP address 
wins the querier election, and all other  IGMPv2 routers become non-queriers.  
3. All the non-queriers start a timer, known as other querier present timer. If a router receives an 
IGMP query from the querier before the timer expires,  it resets this timer. Otherwise, it assumes the 
querier to have timed out and initiate s a new querier election process.  
Leave group mechanism  
I n  I GM P v 1,  wh e n  a  h o s t  l e ave s  a  m u l t ic a s t  g ro u p,  i t  d o e s  n o t  s e n d  a ny  n o t i fic a t io n  t o  t h e  m u l t ic as t  ro u t e r.  
The multicast router relies on the host response ti meout timer to determine whether a group has members. 
This adds to the leave latency.  
In IGMPv2, when a host leaves a multicast group, the following steps occur:  
1.  This host sends a leave message to all routers on the local su bnet. The destination address is 
224.0.0.2.  
2.  After receiving the leave message, the querier sends a configurable number of group-specific 
queries to the group that the host is leaving. The destination address field and group address field 
of the message are both filled with the address of  the multicast group that is being queried.  
3. One of the remaining members (if any on the subnet) of the group that is being queried should 
send a membership report within the maximum  response time set in the query messages.  
4. If the querier receives a membership report for the group within the maximum response time, it will 
maintain the memberships of the group. Otherwise,  the querier will assume that no hosts on the 
subnet are still interested in multicast traffic to that group and will stop maintaining the 
memberships of the group.  
Enhancements in IGMPv3 
IGMPv3 is based on and is compatible with IGMP v1 and IGMPv2. It provides hosts with enhanced 
control capabilities and provides enhancements of query and report messages.
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Enhancements in contro l capability of hosts 
IGMPv3 introduced two source filtering modes—Includ e and Exclude. These modes allow a host to join 
a designated multicast group and to choose whether to  receive or reject multicast data from designated 
multicast sources. When a host joins a multicast group, one of the following situation occurs: 
•   If it needs to receive multicast data from specific sources like S1, S2, …, it sends a report with the 
Filter-Mode denoted as Include Sources (S1, S2, …).  
•   If it needs to reject multicast data from specific sources like S1, S2, …, it sends a report with the 
Filter-Mode denoted as Exclude Sources (S1, S2, …).  
As shown in  Figure 32,
 the network comprises two multicast sources, Source 1 (S1) and Source 2 (S2), 
both of which can send multicast data to multicast group  G.  H o s t  B  i s  o n l y  i n t e re s t e d  i n  t h e  m u l t ic a s t  d a t a  
that Source 1 sends to G but not in the data from Source 2.  
Figure 32  Flow paths of source-and-group-specific multicast traffic 
 
 
I n  t h e  c a s e  o f  I G M P v 1  o r  I G M P v 2,  H o s t  B  c a n n o t  s e l e c t  m u l t i c a s t  s o u rc e s  w h e n  i t  j o i n s  m u l t i c a s t  g ro u p  G.  
Therefore, multicast streams from both Source 1 and Source 2 will flow to Host B whether or not it needs 
them.  
When IGMPv3 is running between the hosts and routers, Host B can explicitly express that it needs to 
receive the multicast data that Source 1 sends to multicast group G —denoted as (S1, G), rather than the 
multicast data that Source 2 sends to multicast group G —denoted as (S2, G). Thus, only multicast data 
from Source 1 will be delivered to Host B.  
Enhancements in query and report capabilities 
1.  Query message carrying  the source addresses  
IGMPv3 supports not only general queries (feature  of IGMPv1) and group-specific queries (feature 
of IGMPv2), but also group-an d-source-specific queries.  
{ A general query does not carry a group address or a source address. 
{ A group-specific query carries a group address, but no source address.  
{ A group-and-source-specific query carries a group address and one or more source addresses.   
2. Reports containing multiple group records  
Unlike an IGMPv1 or IGMPv2 report message,  an IGMPv3 report message is destined to 
224.0.0.22 and contains one or more group record s. Each group record contains a multicast 
group address and a multicast source address list.
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Group records fall into the following categories: 
{ IS_IN —The source filtering mode is Include. The re port sender requests the multicast data from 
only the sources defined in the specified multicast source list. 
{  IS_EX—The source filtering mode is Exclude. The report sender requests the multicast data from 
any sources but those defined in the specified multicast source list.  
{ TO_IN —The filtering mode has changed from Exclude to Include. 
{ TO_EX —The filtering mode has changed from Include to Exclude. 
{ ALLOW —The Source Address fields in this group re cord contain a list of the additional sources 
that the system wants to obtain data from, for pac kets sent to the specified multicast address. If 
the change was to an Include source list, these sources are the addresses that were added to 
the list. If the change was to an Exclude source list, these sources are the addresses that were 
deleted from the list. 
{  BLOCK —The Source Address fields in this group re cord contain a list of the sources that the 
system no longer wants to obtain data from, for packets sent to the specified multicast address. 
If the change was to an Include source list,  these sources are the addresses that were deleted 
from the list. If the change was to an Exclude source list, these sources are the addresses that 
were added to the list. 
IGMP SSM mapping 
The IGMP SSM mapping feature enables you to config ure static IGMP SSM mappings on the last-hop 
router to provide SSM support for receiver hosts that are running IGMPv1 or IGMPv2. The SSM model 
assumes that the last-hop router has identified the desired multicast sources when receivers join multicast 
groups.  
•   When a host that is running IGMPv3 joins a multicast group, it can explicitly specify one or more 
multicast sources in its IGMPv3 report.  
•   A  h o s t  t h a t  i s  r u n n i n g  I G M P v 1  o r  I G M P v 2,  h o w e v e r,  c a n n o t  s p e c i f y  m u l t i c a s t  s o u rc e  a d d re s s e s  i n  i t s  
report. In this case, you must configure the IG MP SSM mapping feature to translate the (*, G) 
information in the IGMPv1 or IGMPv2 report into (G, INCLUDE, (S1, S2...)) information. 
Figure 33  Network diagram
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As shown in  Figure 33, on an SSM network, Host A, Host B, and Host C are running IGMPv1, IGMPv2, 
and IGMPv3 respectively. To provide SSM service for all the hosts if IGMPv3 is not available on Host A 
and Host B, you must configure the IGMP SSM mapping feature on Router A. 
W i t h  t h e  I G M P  SS M  m a p p i n g  f e a t u re  c o n f i g u re d ,  w h e n  R o u t e r  A  r e c e i v e s  a n  I G M P v 1  o r  I G M P v 2  re p o r t,  
it checks the multicast group address G carried in the message and does the following: 
•   If G is not in the SSM group range, Router A cannot provide the SSM service but can provide the 
ASM service. 
•   If G is in the SSM group range but no IGMP SSM  mappings that correspond to the multicast group 
G  h a v e  b e e n  c o n f i g u r e d  o n  R o u t e r  A ,  R o u t e r  A   cannot provide SSM service and drops the message. 
•   If G is in the SSM group range and the IGMP SSM mappings have been configured on Router A for 
multicast group G, Router A translates the (*, G) information in the IGMP report into (G, INCLUDE, 
(S1, S2...)) information based on the configured IGMP SSM mappings and provides SSM service 
accordingly. 
 
  NOTE: 
The IGMP SSM mapping feature does not process IGMPv3 reports. 
 
For more information about the SSM group range, see  Configuring PIM (available only on the HP 5500 
EI) 
IGMP proxying 
In some simple tree-shaped topologies, it is no t necessary to configure complex multicast routing 
protocols, such as PIM, on the boundary devices. Instead, you can configure IGMP proxying on these 
devices. With IGMP proxying configured, the device serves as a proxy for the downstream hosts to send 
IGMP messages, maintain group memberships, an d implement multicast forwarding based on the 
memberships. In this case, each boundary device is a  host but no longer a PIM neighbor to the upstream 
device.  
Figure 34  Network diagram 
 
 
As shown in Figure 34, the f ollowing types of interfaces are defined on an IGMP proxy device: 
 
Query from Router A
Report from Router B
Ethernet
Router interface Host interface
Proxy & QuerierRouter BQuerier
Router A
Host B
Receiver
Host A Receiver
Host C
Query from Router B
Report from Host
PIM domain
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•  Upstream interface —Also called the proxy interface. A pro xy interface is an interface on which 
IGMP proxying is configured. It is in the direction toward the root of the multicast forwarding tree. 
An upstream interface acts as a host that is running IGMP. Therefore, it is also called the host 
interface.  
•   Downstream interface —An interface that is running IGMP an d is not in the direction toward the 
root of the multicast forwarding tree. A downstream interface acts as a router that is running IGMP. 
Therefore, it is also called the router interface.  
A device with IGMP proxying configured maintain s a group membership database, which stores the 
group memberships on all the downstream interfaces.  Each entry comprises the multicast address, filter 
mode, and source list. Such an entry is a collectio n of members in the same multicast group on each 
downstream interface.  
A proxy device performs host functions on the upstre am interface based on the database. It responds to 
queries according to the information in the databas e or sends join/leave messages when the database 
changes. On the other hand, the proxy device performs  router functions on the downstream interfaces by 
participating in the querier election, sending queries, and maintaining memberships based on the 
reports.  
IGMP support for VPNs 
IGMP maintains group memberships on a per-interfac e base. After receiving an IGMP message on an 
interface, IGMP processes the packet within the VPN that  the interface belongs to. If IGMP that runs in a 
VPN needs to exchange information with another multic ast protocol, it passes the information only to the 
protocol that runs in this VPN.  
Protocols and standards  
•   RFC 1 112 ,   Host Extensions for IP Multicasting  
•   RFC 2236,  Internet Group Management Protocol, Version 2  
•   RFC 3376,  Internet Group Management Protocol, Version 3  
•   RFC 4605,  Internet Group Management Protocol (IGMP) /Multicast Listener Discovery (MLD) -Based 
Multicast Forwarding (IGMP/MLD Proxying)  
IGMP configuration task list  
 
Task  Remarks  
Configuring basic IGMP 
functions   Enabling IGMP 
Required 
Configuring IGMP versions Optional
 
Configuring static joining  Optional
 
Configuring a multicast group filter  Optional
 
Setting the maximum number of multicast groups 
that an interface can join  Optional
 
Adjusting IGMP performance  Configuring IGMP message options 
Optional
 Configuring IGMP query and response 
parameters  Optional
 
Configuring IGMP fast-leave processing  Optional
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