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HP 5500 Ei 5500 Si Switch Series Configuration Guide

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Step Command Remarks 
3.  Configure the maximum 
number of downstream nodes 
for a single IPv6 multicast 
forwarding entry.  multicast ipv6 forwarding-table 
downstream-limit 
limit  Optional. 
128 by default. 
 
Displaying and maintaining IPv6 multicast routing 
and forwarding 
 
Task Command Remarks 
Display the IPv6 multicast boundary 
information.  display multicast ipv6 boundary 
{ group  
[  ipv6-group-address  [ prefix-length ] ] | scope 
[ scope-id  ] } [ interface  interface-type 
interface-number  ] [ | { begin  | exclude  | 
include  } regular-expression ]   Available in any 
view 
Display the information of the IPv6 
multicast forwarding table.  display multicast ipv6 forwarding-table 
[ ipv6-source-address
 [ prefix-length ] | 
ipv6-group-address  [ prefix-length ] | 
incoming-interface  { interface-type 
interface-number  | register  } | 
outgoing-interface { exclude  | include  | 
match } { interface-type interface-number  | 
register  } | statistics  | slot  slot-number  ] * 
[ port-info  ] [ | { begin |  exclude | include  } 
regular-expression  ]   Available in any 
view
 
Display the DF information of the IPv6 
multicast forwarding table.  display multicast ipv6 forwarding-table
 
df-info  [ rp-address  ] [ slot slot-number  ] [ | 
{  begin |  exclude | include  } 
regular-expression  ]  Available in any 
view 
Display the information of the IPv6 
multicast routing table.
 display multicast ipv6 routing-table
 
[ ipv6-source-address  [ prefix-length ] |  
ipv6-group-address  [ prefix-length ] | 
incoming-interface  { interface-type 
interface-number  | register  } | 
outgoing-interface { exclude  | include  | 
match } { interface-type interface-number  | 
register  } ] * [ | { begin |  exclude | include  } 
regular-expression  ]  Available in any 
view
 
Display the RPF route information of the 
specified IPv6 multicast source.
 display multicast ipv6 rpf-info
 
ipv6-source-address  [ ipv6-group-address  ] [ | 
{  begin |  exclude | include  } 
regular-expression  ]  Available in any 
view
 
Clear forwarding entries from the IPv6 
multicast forwarding table.
 reset multicast ipv6 forwarding-table
 
{ { ipv6-source-address  [ prefix-length ] | 
ipv6-group-address  [ prefix-length ] | 
incoming-interface  { interface-type 
interface-number  | register  } } * | all  }  Available in user 
view
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    							 306 
Task Command Remarks 
Clear routing entries from the IPv6 
multicast routing table. reset multicast ipv6 routing-table
 
{ { ipv6-source-address  [ prefix-length ] | 
ipv6-group-address  [ prefix-length ] | 
incoming-interface  { interface-type 
interface-number  | register  } } * | all  }  Available in user 
view
 
 
For more information about designated forwarder (DF), see  Configuring IPv6 PIM (available only on the 
HP 5
500 EI) . 
 
 IMPORTANT: 
The 
reset  command clears the information in the IPv6 multicast routin
g table or the multicast forwarding 
table and might cause transmission failure of IPv6 multicast information.   
When a routing entry is deleted from the IPv6 multic ast routing table, the corresponding forwarding entry 
is also deleted from the IPv6 multicast forwarding table.  
When a forwarding entry is deleted from the IPv6 mu lticast forwarding table, the corresponding routing 
entry is also deleted from the IPv6 multicast routing table. 
Troubleshooting IPv6 multicast policy configuration  
Abnormal termination of IPv6 multicast data  
Symptom 
•   A host sends an MLD report announcing its joining an IPv6 multicast group (G). However, no 
member information about the IPv6 multicast group (G) exists on the intermediate router. The 
intermediate router can receive IPv6 multicast packets successfully, but the packets cannot reach the 
stub network. 
•   The interface of the intermediate router receives  the IPv6 multicast packets, but no corresponding (S, 
G) entry exists in the IPv6 PIM routing table. 
Analysis 
•   The multicast ipv6 boundary  command filters IPv6 multicast packets received on an inter face. If an 
IPv6 multicast packet fails to match the IPv6 ACL rule of this command, IPv6 PIM will create no 
routing entry. 
•   In addition, the  source-policy c o m m a n d  i n  I P v 6  P I M  f i l t e r s  r e c e i v e d  I P v 6  m u l t i c a s t  p a c k e t s .  I f  a n  I P v 6  
multicast packet fails to match the IPv6 ACL rule of this command, IPv6 PIM will not create a routing 
entry, either. 
Solution  
1.  Use the  display current-configuration  command to display the IPv6 ACL rule configured on the 
multicast forwarding boundary. Change the IPv6 ACL rule used in the  multicast ipv6 boundary 
command so that the source IP address of the IP v6 multicast packets and the IPv6 multicast group 
address can both match the IPv6 ACL rule. 
2.  View the configuration of the multicast filter. Use the  display current-configuration command to 
display the configuration of the IPv6 multicast  filter. Change the IPv6 ACL rule used in the
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source-policy command so that the source IP address of the IPv6 multicast packets and the IPv6 
multicast group address can both match the IPv6 ACL rule.
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    							 308 
Configuring MLD (available only on the HP 
5500 EI) 
Overview 
An IPv6 router uses the Multicast Listener Discovery (MLD) protocol to discover the presence of multicast 
listeners on the directly attached subnets. Multicast listeners are nodes that want to receive IPv6 multicast 
packets. 
Through MLD, the router can determine whether any IPv6 multicast listeners exist on the directly 
connected subnets, put corresponding records in the database, and maintain timers related to IPv6 
multicast addresses. 
Routers running MLD use an IPv6 unicast link-local address as the source address to send MLD messages. 
MLD messages are Internet Control Message Protocol for IPv6 (ICMPv6) messages. All MLD messages 
are confined to the local subnet, with a hop count of 1. 
The term router in this document refers to both routers and Layer 3 switches. 
The term interface in the MLD 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 ). 
MLD versions 
•  MLDv1 (defined in RFC 2710), which is derived from IGMPv2. 
•   MLDv2 (defined in RFC 3810), which is derived from IGMPv3. 
All MLD versions support the Any-Source Multicast (ASM) model. In addition, MLDv2 can directly 
implement the Source-Specific Multicast (SSM) model, but MLDv1 must work with the MLD SSM mapping 
function to implement SSM service.  
For more information about the ASM and SSM models, see  Multicast overview. 
How MLDv1 works 
MLDv1 implements IPv6 multicast listener management based on the query/response mechanism. 
MLD querier election 
All IPv6 multicast routers on the same subnet can monitor MLD listener report messages (often called 
reports) from hosts, but only one router is needed for sending MLD query messages (often called 
queries). A querier election mechanism determines  which router will act as the MLD querier on the 
subnet.  
1.  Initially, every MLD router assumes itself as the querier and sends MLD general query messages 
(often called general queries) to all hosts and  routers on the local subnet. The destination address 
is FF02::1.
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    							 309 
2.
 
After receiving a general query, every MLD router  compares the source IPv6 address of the query 
message with its own interface address. After com parison, the router with the lowest IPv6 address 
wins the querier election and all ot her routers become non-queriers.  
3. All the non-queriers start a timer called the other querier present timer. If a router receives an 
MLD query from the querier before the timer expires,  it resets this timer. Otherwise, it assumes that 
the querier has timed out and initiate s a new querier election process.  
Joining an IPv6 multicast group 
Figure 81 MLD queries and reports 
 
 
Assume that Host B and Host C will receive IPv6 multicast data addressed to IPv6 multicast group G1, 
and Host A will receive IPv6 multicast data addressed to G2, as shown in  Figure 81. T
 he following 
process describes how the hosts join the IPv6 multicast groups and how the MLD querier (Router B in the 
figure) maintains the IPv6 multicast group memberships:  
1.  The hosts send unsolicited MLD repo rts to the addresses of the IPv6 multicast groups that they will 
join, without having to wait for the  MLD queries from the MLD querier.  
2. The MLD querier periodically mult icasts MLD queries (with the destination address of FF02::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 MLD report to the IPv6 multicast group addre ss of G1, to announce its membership for G1. 
Assume that Host B sends the report message. Afte r hearing the report from Host B, Host C, which 
is on the same subnet as Host B, suppresses its own report for G1, because the MLD routers (Router 
A and Router B) have already known that at least one host on the local subnet is interested in G1. 
This mechanism, known as the MLD  report suppression, 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 IPv6 multicast group 
address of G2.  
5.  Through the query/report process, the MLD routers learn that members of G1 and G2 are 
attached to the local subnet, and the IPv6 multicast  routing protocol (for example, IPv6 PIM) that is 
running on the routers generates (*, G1) and (*, G2) multicast forwarding entries. These entries 
will be the basis for subsequent IPv6 multicast fo rwarding, where * represents any IPv6 multicast 
source.  
Query
Report
Querier
Host A (G2) Host B
(G1) Host C
(G1)
Ethernet Router A
Router B
IPv6 network
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    							 310 
6.
 
When the IPv6 multicast data addres sed to G1 or G2 reaches an MLD router, because the (*, G1) 
and (*, G2) multicast forwarding entries exist on  the MLD router, the router forwards the IPv6 
multicast data to the local subnet, and then the receivers on the subnet receive the data.  
Leaving an IPv6 multicast group 
When a host leaves a multicast group, the following occur:  
1.  The host sends an MLD done message to all IPv6 multicast routers on the local subnet. The 
destination address is FF02::2. 
2. After receiving the MLD done message, the querier sends a configurable number of 
multicast-address-specific queries to  the group that the host is leaving. The destination address field 
and group address field of the message are both fill ed with the address of the IPv6 multicast group 
that is being queried.  
3.  One of the remaining members (if any on the subnet) of the group being queried should send a 
report within the time of the maximum re sponse delay set in the query messages.  
4. If the querier receives a report for the group  within the maximum response delay time, it will 
maintain the memberships of the IPv6 multicast gr oup. Otherwise, the querier will assume that no 
hosts on the subnet are still interested in IPv6 mu lticast traffic addressed to that group and will stop 
maintaining the memberships of the group.  
How MLDv2 works 
Compared with MLDv1, MLDv2 provides the following new features:  
IPv6 multicast group filtering 
MLDv2 has introduced IPv6 multicast source filtering mo des (Include and Exclude), so that a host not only 
can join a designated IPv6 multicast group, but also can specify to receive or reject multicast data from 
designated IPv6 multicast sources. When a host joins an IPv6 multicast group, one of the following 
situation occurs: 
•   I f  i t expe cts  I Pv6  mu l tic ast data from specific  I P v6  mu l ticast sources  l ike  S1, S2, … , i t sends  a re por t  
with Filter-Mode denoted as Include Sources (S1, S2, …).  
•   If it does not expect I Pv6 multicast data from specific I Pv6 multicast sources like S1, S2, …, it sends 
a report with Filter-Mode denoted as Exclude Sources (S1, S2, …).  
As shown in  Figure 82,
 the network comprises two IPv6 multicast sources, Source 1 (S1) and Source 2 
(S2), both of which can send IPv6 multicast data to IPv6 multicast group G. Host B is interested only in 
the IPv6 multicast data that Source 1 sends to G but not in the data from Source 2.
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Figure 82 Flow paths of multicast-address-and- source-specific multicast traffic 
 
 
In the case of MLDv1, Host B cannot select IPv6 multicast sources when it joins IPv6 multicast group G. 
Therefore, IPv6 multicast streams from both Source 1 and Source 2 will flow to Host B whether it needs 
them or not.   
When MLDv2 is running on the hosts and routers, Host B can explicitly express its interest in the IPv6 
multicast data that Source 1 sends to G (denoted as  (S1, G)), rather than the IPv6 multicast data that 
Source 2 sends to G (denoted as (S2, G)). Thus, only IPv6 multicast data from Source 1 will be delivered 
to Host B.  
MLD state 
A multicast router that is running MLDv2 maintains the multicast address state per multicast address per 
attached subnet. The multicast address state consists of the following information: 
•   Filter mode —The router keeps tracing the Include or Exclude state. 
•   List of sources —The router keeps tracing the newly added or deleted IPv6 multicast source. 
•   Timers —Filter timers, including the time that the router waits before switching to the Include mode 
after an IPv6 multicast address times out, the source timer for source recording, and so on. 
Receiver host state listening  
By listening to the state of receiver hosts, a multicast router running MLDv2 records and maintains 
information of hosts joining the source group on the attached subnet. 
MLD messages 
The following descriptions are based on MLDv2 messages. 
MLD query message 
An MLD querier learns the multicast listening state of neighbor interfaces by sending MLD query 
messages. The dark area in  Figure 83 s
hows the MLDv1 message format.
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Figure 83 MLDv2 query message format 
 
 
Table 9 MLDv2 query message field description 
Field Descri
ption 
Type = 130   Message type. For a query message, this field is set to 130.
 
Code  Initialized to zero.
 
Checksum
  Standard IPv6 checksum.
 
Maximum Response Delay  Maximum response delay allowed before a host sends a report message.
Reserved
  Reserved field and initialized to zero.
 
Multicast Address 
• This field is set to 0 in a general query message. 
• It is set to a specific IPv6 multicast address in a 
multicast-address-specific query message or 
multicast-address-and-source-specific query message.  
S
  Flag indicating whether a router up
dates the timer for suppression after 
receiving a query message.  
QRV
  Querier’s Robustness Variable.
 
QQIC
  Querier’s Query Interval Code. 
 
Multicast Address (128 bits)
Type = 130Code
07 1
5 31Checksum
Maximum Response DelayReserved
ReservedSQRVQQICNumber of Sources (n)
34
Source Address [1] (128 bits)
Source Address [n] (128 bits)
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Field Description 
Number of Sources 
• This field is set to 0 in a general query message or a 
multicast-address-specific query message. 
• This field represents the number of source addresses in a 
multicast-address-and-source-specific query message.  
Source Address( i )
 IPv6 multicast source address in a multicast-address-specific query 
message (i = 1, 2, .., n, where n represents the number of multicast source 
addresses.)
 
 
MLD report message 
A host sends an MLD report message to repo rt the current multicast listening state. Figure 84 sh ows the 
MLD report message format. 
Figure 84  MLDv2 report message format 
 
 
Table 10 MLDv2 report message field description 
Field   Descri
ption 
Type = 143
  Message type. For a report message, this field is set to 143.
 
Reserved  The Reserved fields are set to 0 
on transmission and ignored on 
reception.  
Checksum   Standard IPv6 checksum.
 
Number of Multicast Address Records
 This field indicates how many IPv6 multicast address records are 
present in this report message.
 
Multicast Address Record(i) This field represents information 
of each IPv6 multicast address 
the host listens to on the interface from which the report message 
is sent, including record type, IPv6 multicast address, and IPv6 
multicast source address on the sender (i= 1, 2, ... m, where m 
represents the number of IPv6 multicast address records).
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    							 314 
 
MLD SSM mapping 
The MLD SSM mapping feature enables you to configure static MLD SSM mappings on the last hop router 
to provide SSM support for receiver hosts that are running MLDv1. The SSM model assumes that the last 
hop router has identified the desired IPv6 multicast sources when receivers join IPv6 multicast groups. 
•  W h e n  a n  M L D v 2  e n a b l e d  h o s t  j o i n s  a  m u l t i c a s t  g r o u p ,  i t  c a n  e x p l i c i t l y  s p e c i f y  o n e  o r  m o r e  m u l t i c a s t  
sources in its MLDv2 report. 
•   An MLDv1-enabled host, however, cannot specify multicast source addresses in its MLDv1 report. 
You must configure the MLD SSM mapping feature to translate the (*, G) information in the MLDv1 
report into (G, INCLUDE, (S1, S2...)) information. 
Figure 85  Network diagram 
 
 
On the IPv6 SSM network in Figure 85, Host A and Host B are running MLDv1 and Host C is running 
MLDv2. To provide SSM service for Host A and Host B, you must configure the MLD SSM mapping 
feature on Router A. 
With the MLD SSM mapping feature configured, when Router A receives an MLDv1 report, it checks the 
IPv6 multicast group address G carried in the message. 
•   If G is not in the IPv6 SSM group range, Router A cannot provide the SSM service but can provide 
the ASM service. 
•   If G is in the I Pv6 SSM group range but no MLD SSM mappings have been configured for the I Pv6 
multicast group G on Router A, Router A cannot provide SSM service and drops the packet.  
•   If G is in the I Pv6 SSM group range, and the MLD SSM mappings have been configured on Router 
A for multicast group G, Router  A translates the (*, G) information in the MLD report into (G, 
INCLUDE, (S1, S2...)) information based on the configured MLD SSM mappings and provides SSM 
service accordingly. 
 
  NOTE: 
The MLD SSM mapping feature does not process MLDv2 reports. 
 
For more information about the IPv6 SSM group range, see  Configuring IPv6 PIM (available only on the 
HP 5
500 EI) . 
MLDv1 report
MLDv2 report
Router AQuerier
Host A (MLDv1)
IPv6 SSM
Receiver Host B (MLDv1)Receiver
Host C (MLDv2)Receiver
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