HP 5500 Ei 5500 Si Switch Series Configuration Guide
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315 MLD proxying In some simple tree-shaped topologies, you do not need to configure complex IPv6 multicast routing protocols, such as IPv6 PIM, on the boundary devices. Instead, you can configure MLD proxying on these devices. With MLD proxying configured, the device serves as a proxy for the downstream hosts to send MLD messages, maintain group memberships, and implement IPv6 multicast forwarding based on the memberships. In this case, the MLD proxy device is a host but no longer an IPv6 PIM neighbor to the upstream device. Figure 86 Network diagram As shown in Figure 86, an MLD proxy device has the following types of interfaces: • Upstream interface —Also called the proxy interface. A pro xy interface is an interface on which M L D p r o x yi n g i s c o n f i g u r e d . I t i s i n t h e d i r e c t i o n t o w a r d t h e r o o t o f t h e m u l t i c a s t f o r w a r d i n g t r e e . A n upstream interface acts as a host that is running MLD, and is also called a host interface. • Downstream interface —An interface that is running MLD and not in the direction toward the root of the multicast forwarding tree. A downstream interfac e acts as a router that is running MLD, and is also called a router interface. A device with MLD proxying configured maintain s a group membership database, which stores the group memberships on all the downstream interfaces in this database. Each entry comprises the multicast address, filter mode, and source list. Such an entry is a collection 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 the queries according to the information in the database or sends join/leave messages when the database changes. The proxy device performs rout er functions on the downstream interfaces by participating in the querier election, sending queries, and maintaining memberships based on the reports. Protocols and standards • RFC 2710, Multicast Listener Discovery (MLD) for IPv6 • RFC 3810, Multicast Listener Discovery Version 2 (MLDv2) for IPv6
316 • RFC 4605, Internet Group Management Protocol (IGMP) /Multicast Listener Discovery (MLD) -Based Multicast Forwarding (IGMP/MLD Proxying) MLD configuration task list Task Remarks Configuring basic MLD functions Enabling MLD Required Configuring the MLD version Option Configuring static joining Optional Configuring an IPv6 multicast group filter Optional Setting the maximum number of IPv6 multicast groups that an interface can join Optional Adjusting MLD performance Configuring MLD message options Optional Configuring MLD query and response parameters Optional Configuring MLD fast-leave processing Optional Enabling the MLD host tracking function Optional Setting the DSCP value for MLD messages Optional Configuring MLD SSM mapping Enabling MLD SSM mapping Optional Configuring MLD SSM mappings Optional Configuring MLD proxying Enabling MLD proxying Optional Configuring IPv6 multicast forwarding on a downstream interface Optional NOTE: • In MLD view, the configuration is effective globally. In interface view, the configuration is effective on only the current interface. • If no confi guration is performed in interface view, the global configuration in MLD view will apply to that interface. Configurations performed in interface view take precedence over those performed in MLD view. Configuring basic MLD functions Configuration prerequisites Before you configure basic MLD functions, complete the following tasks: • Enable IPv6 forwarding and configure an IPv6 unic ast routing protocol so that all devices in the domain can be interoperable at the network layer. • Configure IPv6 PIM-DM or IPv6 PIM-SM. • Determine the MLD version.
317 • Determine the IPv6 multicast group address and IPv6 multicast source address for static group member configuration. • Determine the ACL rule for IPv6 multicast group filtering. • Determine the maximum number of IPv6 multicast groups that an interface can join. Enabling MLD Enable MLD on the interface on which IPv6 multicast group memberships will be created and maintained. To e n ab l e M L D : Step Command Remarks 1. Enter system view. system-view N/A 2. Enable IPv6 multicast routing. multicast ipv6 routing-enable Disable by default 3. Enter interface view. interface interface-type interface-number N/A 4. Enable MLD. mld enable Disabled by default For more information about the multicast ipv6 routing-enable command, see IP Multicast Command Reference . Configuring the MLD version Because MLD message types and formats vary with MLD versions, the same MLD version should be configured for all routers on the same subnet before MLD can work properly. Configuring an MLD version globally Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Configure an MLD version globally. version version-number MLDv1 by default Configuring an MLD version on an interface Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure an MLD version on the interface. mld version version-number MLDv1 by default
318 Configuring static joining After an interface is configured as a static member of an IPv6 multicast group or an IPv6 multicast source and group, it will act as a virtual member of the IPv6 multicast group to receive IPv6 multicast data addressed to that IPv6 multicast group for the purpose of testing IPv6 multicast data forwarding. Configuration guidelines Before you can configure an interface of an IPv6 PIM-SM device as a static member of an IPv6 multicast group or an IPv6 multicast source and group, if the interface is IPv6 PIM-SM enabled, it must be an IPv6 P I M - S M D R . I f t h i s i n t e r f a c e i s M L D e n a b l e d b u t n o t I P v 6 P I M - S M e n a b l e d, i t m u s t b e a n M L D q u e ri e r. Fo r more information about IPv6 PIM-SM and a DR, see Configuring IPv6 PIM (available only on the HP 5 500 EI) . A static member port does not respond to queries from the MLD querier. When you configure an interface as a static member port or remove this configuration on the interface, the interface does not unsolicitedly send any MLD report or an MLD done message. In othe r words, the interface is not a real member of the IPv6 multicast group or the IPv6 multicast and source group. Configuration procedure To configure a static member of an IPv6 multicast group or an IPv6 multicast source and group: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure a static member of an IPv6 multicast group or an IPv6 multicast source and group. mld static-group ipv6-group-address [ source ipv6-source-address ] By default, an interface is not a static member of any IPv6 multicast group or IPv6 multicast source and group. Configuring an IPv6 multicast group filter To restrict the hosts on the network attached to an interface from joining certain IPv6 multicast groups, you can set an IPv6 ACL rule on the interface so th at the interface maintains only the IPv6 multicast groups matching the criteria. To configure an IPv6 multicast group filter: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure an IPv6 multicast group filter. mld group-policy acl6-number [ version-number ] By default, no IPv6 group filter is configured on the interface. That is, hosts on the current interface can join any valid multicast group.
319 Setting the maximum number of IPv6 multicast groups that an interface can join Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure the maximum number of IPv6 multicast groups that the interface can join. mld group-limit limit 1000 by default. NOTE: This configuration takes effect for dynamically join ed IPv6 multicast groups but not the statically configured multicast groups. Adjusting MLD performance For the configuration tasks in this section: • In MLD view, the configuration is effective globally. In interface view, the configuration is effective only on the current interface. • If the same function or parameter is configur ed in both MLD view and interface view, the configuration performed in interface view is given priority, regardless of the configuration order. Configuration prerequisites Before adjusting MLD performance, complete the following tasks: • Enable IPv6 forwarding and configure an IPv6 unic ast routing protocol so that all devices in the domain can be interoperable at the network layer. • Configure basic MLD functions. • Determine the startup query interval. • Determine the startup query count. • Determine the MLD query interval. • Determine the MLD querier’s robustness variable. • Determine the maximum response delay of MLD general query messages. • Determine the MLD last listener query interval. • Determine the MLD other querier present interval. • Determine the DSCP value for MLD messages. Configuring MLD message options MLD queries include multicast-address-specific queries and multicast-address-and-source-specific queries, and IPv6 multicast groups change dynamically, so a device cannot maintain the information for all IPv6 multicast sources and groups. Therefore, a router might receive IPv6 multicast packets addressed to IPv6
320 multicast groups that have no members on the local subnet. In this case, the Router-Alert option carried in the IPv6 multicast packets is useful for the router to determine whether to deliver the IPv6 multicast packets to the upper-layer protocol for processing. For more information about the Router-Alert option, see RFC 21 13 . An MLD message is processed differently depending on whether it carries the Router-Alert option in the IPv6 header, as follows: • For compatibility, the device by default ignores the Router-Alert option and processes all received MLD messages, no matter whether the MLD messag es carry the Router-Alert option or not. • To enhance device performance, avoid unnecessary costs, and ensure protocol security, configure the device to discard MLD messages that do not carry the Router-Alert option. Configuring the Router-Alert option for MLD messages globally Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Configure the interface to discard any MLD message without the Router-Alert option. require-router-alert By default, the device does not check MLD messages for the Router-Alert option. 4. Enable the insertion of the Router-Alert option into MLD messages. send-router-alert By default, MLD messages carry the Router-Alert option. Configuring the Router-Alert option on an interface Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure the interface to discard any MLD message without the Router-Alert option. mld require-router-alert By default, the device does not check MLD messages for the Router-Alert option. 4. Enable the insertion of the Router-Alert option into MLD messages. mld send-router-alert By default, MLD messages carry the Router-Alert option. Configuring MLD query and response parameters MLD query and response parameters On startup, the MLD querier sends MLD general qu eries at the startup query interval, which is one-quarter of the MLD query interval. The number of queries, or the startup query count, is user configurable.
321 After startup, the MLD querier periodically sends MLD general queries at the MLD query interval to check for IPv6 multicast group members on the network. You can modify the query interval based on the actual condition of the network. The MLDv1 querier sends MLD multicast-address-specific queries at the MLD last listener query interval when it receives an MLD done message. The MLDv2 querier sends MLD multicast-address-and-source-specific queries at the MLD last listener query interval when it receives a multicast group and multicast source mapping change report. The number of queries, or the last listener query count, equals the robustness variable (the maximum number of packet retransmissions). A multicast listening host starts a timer for each IPv6 multicast group that it has joined when it receives an MLD query (general query, multicast-address-specific query, or multicast-address-and-source-specific query). The timer is initialized to a random value in the range of 0 to the maximum response delay advertised in the MLD query message. When the timer decreases to 0, the host sends an MLD membership report message to the IPv6 multicast group. Configuration guidelines To speed up the response of hosts to MLD queries and avoid simultaneous timer expirations causing MLD report traffic bursts, you must properly set the maximum response delay. • For MLD general queries, the maximum response delay is set by the max-response-time command. • For MLD multicast-address-specific query and multicast-address-and-source-specific query messages, the maximum response delay equals the last listener query interval. When multiple multicast routers exist on the same subnet, the MLD querier is responsible for sending MLD query messages. If a non-querier router receives no MLD query from the querier when the other querier present interval expires, it considers the querier as having failed and starts a new querier election. Otherwise, the non-querier resets the other querier present timer. To avoid frequent MLD querier changes, set the other querier present interval greater than the MLD query interval. To avoid incorrect multicast group member removals, set the MLD query interval greater than the maximum response delay for MLD general queries. Configuration procedure To configure MLD query and response parameters globally: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Configure the MLD querier’s robustness variable. robust-count robust-value 2 times by default. A higher robustness variable makes the MLD querier more robust but results in a longer IPv6 multicast group timeout time. 4. Configure the startup query interval. startup-query-interval interval By default, the startup query interval is 1/4 of the MLD query interval. 5. Configure the startup query count. startup-query-count value By default, the startup query count is set to the MLD querier’s robustness variable.
322 Step Command Remarks 6. Configure the MLD query interval. timer query interval 125 seconds by default. 7. Configure the maximum response delay for MLD general query messages. max-response-time interval 10 seconds by default. 8. Configure the MLD last listener query interval. last-listener-query-interval interval 1 second by default. 9. Configure the MLD other querier present interval. timer other-querier-present interval By default, the other querier present interval is determined by the formula Other querier present interval (in seconds) = [ MLD query interval ] × [ MLD querier’s robustness variable ] + [ maximum response delay for MLD general query ] /2. To configure MLD query and respon se parameters on an interface: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure the MLD querier’s robustness variable. mld robust-count robust-value 2 times by default. 4. Configure the startup query interval. mld startup-query-interval interval By default, the startup query interval is 1/4 of the MLD query interval. 5. Configure the startup query count. mld startup-query-count value By default, the startup query count is the same as the robustness variable. 6. Configure the MLD query interval. mld timer query interval 125 seconds by default. 7. Configure the maximum response delay for MLD general query messages. mld max-response-time interval 10 seconds by default. 8. Configure the MLD last listener query interval. mld last-listener-query-interval interval 1 second by default. 9. Configure the MLD other querier present interval. mld timer other-querier-present interval By default, the other querier present interval is determined by the formula Other querier present interval (in seconds) = [ MLD query interval ] × [ MLD querier’s robustness variable ] + [ maximum response delay for MLD general query ] /2.
323 Configuring MLD fast-leave processing In some applications, such as ADSL dial-up networking, only one multicast receiver host is attached to a port of the MLD querier. To allow fast response to the MLD done messages of the host when it switches frequently from one IPv6 multicast group to another, you can enable MLD fast-leave processing on the MLD querier. With fast-leave processing enabled, after receiving an MLD done message from a host, the MLD querier sends a leave notification to the upstream immediately without first sending MLD multicast-address-specific queries. In this way, the leave latency is reduced on one hand, and the network bandwidth is saved on the other hand. Configuring MLD fast-leave processing globally Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Configure MLD fast-leave processing. fast-leave [ group-policy acl6-number ] Disabled by default. Configuring MLD fast-leave pr ocessing on an interface Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Configure MLD fast-leave processing. mld fast-leave [ group-policy acl6-number ] Disabled by default. NOTE: The MLD fast-leave processing configuration is effectiv e on Layer 3 interfaces other than VLAN interfaces, including Layer 3 Ethernet ports, Layer 3 a ggregate interfaces, and Tunnel interfaces. Enabling the MLD host tracking function With the MLD host tracking function, the switch can record the information of the member hosts that are receiving IPv6 multicast traffic, including the host IPv6 address, running duration, and timeout time. You can monitor and manage the member hosts a ccording to the recorded information. Enabling the MLD host tracking function globally Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Configure the MLD host tracking function globally. host-tracking Disabled by default
324 Enabling the MLD host tracking function on an interface Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Enable the MLD host tracking function on the interface. mld host-tracking Disabled by default Setting the DSCP value for MLD messages Step Command Remarks 1. Enter system view. system-view N/A 2. Enter MLD view. mld N/A 3. Set the DSCP value for MLD messages. dscp dscp-value Optional. By default, the DSCP value in MLD messages is 48. Configuring MLD SSM mapping Because of some possible restrictions, some receiver hosts on an SSM network might run MLDv1. To provide SSM service support for these receiver hosts, you need to configure the MLD SSM mapping feature on the last hop router. Configuration prerequisites Before you configure the MLD SSM mapping feature, complete the following tasks: • Enable IPv6 forwarding and configure an IPv6 unic ast routing protocol so that all devices in the domain can be interoperable at the network layer. • Configure basic MLD functions. Enabling MLD SSM mapping Step Command Remarks 1. Enter system view. system-view N/A 2. Enter interface view. interface interface-type interface-number N/A 3. Enable the MLD SSM mapping feature. mld ssm-mapping enable Disabled by default NOTE: To ensure SSM service for all hosts on a subnet, re gardless of the MLD version running on the hosts, enable MLDv2 on the interface that forwards IP v6 multicast traffic onto the subnet.