HP 5500 Ei 5500 Si Switch Series Configuration Guide
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15 Timer Description Message before expiry Action after expiry Dynamic member port aging timer When a port dynamically joins a multicast group, the switch starts an aging timer for the port. When the timer expires, the dynamic member port ages out. IGMP membership report The switch removes this port from the IGMP snooping forwarding table. NOTE: In IGMP snooping, only dynamic ports age out. Static ports never age out. How IGMP snooping works In this section, the involved ports are dynamic ports. For information about how to configure and remove static ports, see Configuring static ports . A switch that runs IGMP snooping performs differen t actions when it receives different IGMP messages. When receiving a general query The IGMP querier periodically sends IGMP general qu eries to all hosts and routers (224.0.0.1) on the local subnet to determine whether any active multicast group members exist on the subnet. After receiving an IGMP general query, the switch forw ards it to all ports in the VLAN (except the port that received the query). The switch also performs the following judgment: • If the port that received the query is a dynamic router port in the router port list of the switch, the switch restarts the aging timer for the port. • If the port is not in its router port list, the switch adds it into its router port list as a dynamic router port and starts an aging timer for the port. When receiving a membership report A host sends an IGMP report to the IGMP querier in the following circumstances: • If the host has been a member of a multicast group, after receiving an IGMP query, the host responds to the query with an IGMP report. • When the host wants to join a multicast group, it sends an IGMP report to the IGMP querier, specifying the multicast group to join. After receiving an IGMP report, the switch forwards it through all the router ports in the VL AN, resolves the address of the reported multicast group. The switch also performs the following judgment: • If no forwarding entry matches the group address, the switch creates a forwarding entry for the group, adds the port that received the IGMP repo rt as a dynamic member port to the forwarding entry, and starts an aging timer for the port. • If a forwarding entry matches the group address, but the port that received the IGMP report is not in the forwarding entry for the group, the switch adds the port as a dynamic member port to the forwarding entry, and starts an aging timer for the port. • If a forwarding entry matches the group address and th e port that received the IGMP report is in the forwarding entry for the group, the switch restarts the aging timer for the port. A switch does not forward an IGMP report through a non-router port. The reason is that if the switch forwards a report message through a member port, all the attached hosts that are monitoring the
16 reported multicast address suppress their own reports after receiving this report according to the IGMP report suppression mechanism. This prevents the swit ch from confirming whether the reported multicast group still has active members attached to that port. For more information about the IGMP report suppression mechanism, see Configuring IGMP (available only on the HP 5500 EI) When receiving a leave message W h e n a n I G M P v 1 h o s t l e a v e s a m u l t i c a s t g r o u p , t h e h o s t d o e s n o t s e n d a n I G M P l e a v e m e s s a g e , a n d t h e switch cannot know immediately that the host has left the multicast group. However, because the host stops sending IGMP reports as soon as it leaves the multicast group, the switch removes the port that connects to the host from the forwarding entry for the multicast group when the aging timer for the port expires. When an IGMPv2 or IGMPv3 host leaves a multicast group, the host sends an IGMP leave message to the multicast router. When the switch receives an IGMP leave message on a dynamic member port, the switch first checks whether a forwarding entry matches the group address in the message, and, if a match is found, whether the forwarding entry for the group contains the dynamic member port. • If no forwarding entry matches the group address, or if the forwarding entry does not contain the port, the switch directly discards the IGMP leave message. • If a forwarding entry matches the group address an d the forwarding entry contains the port, the switch forwards the leave message to all router ports in the VLAN. Because the switch does not know whether any other hosts attached to the port ar e still listening to that group address, the switch does not immediately remove the port from the forwar ding entry for that group. Instead, it restarts the aging timer for the port. After receiving the IGMP leave message, the IGMP querier resolves the multicast group address in the message and sends an IGMP group-specific query to the multicast group through the port that received the leave message. After receiving the IGMP group-specific query, the switch forwards it through all its router ports in the VLAN and all member ports of the multicast group. The switch also performs the following judgment for the port that received the IGMP leave message: • If the port (assuming that it is a dynamic member port) receives an IGMP report in response to the group-specific query before its aging timer expires, it indicates that some host attached to the port is receiving or expecting to receive multicast data for the multicast group. The switch restarts the aging timer for the port. • If the port receives no IGMP report in response to the group-specific query before its aging timer expires, it indicates that no hosts attached to th e port are still listening to that group address. The switch removes the port from the forwarding entry for the multicast group when the aging timer expires. IGMP snooping proxying You can configure the IGMP snooping proxying function on an edge device to reduce the number of IGMP reports and leave messages sent to its upst ream device. The device configured with IGMP snooping proxying is called an IGMP snooping proxy. It is a host from the perspective of its upstream device. Even though an IGMP snooping proxy is a host from the perspective of its upstream device, the IGMP membership report suppression mechanism for hosts do es not take effect on it. For more information about the IGMP report suppression mechanism for hosts, see Configuring IGMP (available only on the HP 5 500 EI).
17 Figure 13 Network diagram As shown in Figure 13, Switch A works as an IGMP snooping proxy. As a host from the perspective of the querier Router A, Switch A represents its attached hosts to send membership reports and leave messages to Router A. Table 6 IGMP message processing on an IGMP snooping proxy IGMP messa ge Actions General query When receiving an IGMP general query, the proxy forwards it to all ports but the receiving port. In addition, the proxy generates a report according to the group memberships it maintains and sends the report out of all router ports. Group-specific query In response to the IGMP group-specific query for a certain multicast group, the proxy sends the report to the group out of all router ports if the forwarding entry for the group still contains a member port. Report After receiving a report for a multicast group, the proxy looks up the multicast forwarding table for the forwarding entry for the multicast group. • If a forwarding entry matches the multicast group and contains the receiving port as a dynamic member port, the proxy restarts the aging timer for the port. • If a forwarding entry matches the multicast group but does not contain the receiving port, the proxy adds the port to the forwarding entry as a dynamic member port and starts an aging timer for the port. • If no forwarding entry matches the multicast group, the proxy creates a forwarding entry for the multicast group, adds the receiving port to the forwarding entry as a dynamic member port, and starts an aging timer for the port. Leave In response to an IGMP leave message for a multicast group, the proxy sends a group-specific query out of the receiving port. After making sure that no member port is contained in the forwarding entry for the multicast group, the proxy sends a le ave message to the group out of all router ports. Host A Receiver Host BHost C Receiver IGMP Querier Router A Proxy & Querier Switch A Query from Router A Report from Switch A Query from Switch A Report from Host IP network
18 Protocols and standards RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches IGMP snooping configuration task list Task Remarks Configuring basic IGMP snooping functions Enabling IGMP snooping Required Specifying the version of IGMP snooping Optional Configuring static multicast MAC address entries Optional Configuring IGMP snooping port functions Setting aging timers for dynamic ports Optional Configuring static ports Optional Configuring a port as a simulated member host Optional Enabling fast-leave processing Optional Disabling a port from becoming a dynamic router port Optional Configuring IGMP snooping querier Enabling IGMP snooping querier Optional Configuring parameters for IG MP queries and responses Optional Configuring the source IP addresses for IGMP queries Optional Configuring IGMP snooping proxying Enabling IGMP snooping proxying Optional Configuring a source IP address for the IGMP messages sent by the proxy Optional Configuring an IGMP snooping policy Configuring a multicast group filter Optional Configuring multicast source port filtering Optional Enabling dropping unknown multicast data Optional Configuring IGMP report suppression Optional Setting the maximum number of multicast groups that a port can join Optional Setting the 802.1p precedence for IGMP messages Optional Enabling multicast group replacement Optional Configuring a multicast user control policy Optional Enabling the IGMP snooping host tracking function Optional Setting the DSCP value for IGMP messages Optional For the configuration tasks in this section: • In IGMP snooping view, configurations that you make are effective in all VLANs. In VLAN view, configurations that you make are effective on only the ports that belong to the current VLAN. For a given VLAN, a configuration that you make in IGMP snooping view is effective only if you do not make the same configuration in VLAN view.
19 • In IGMP snooping view, configurations that you make are effective on all ports. In Layer 2 Ethernet interface view or Layer 2 aggregate interface view, configurations that you make are effective only on the current port. In port group view, configuratio ns that you make are effective on all ports in the current port group. For a given port, a configuration that you make in IGMP snooping view is effective only if you do not make the same configuration in Layer 2 Ethernet interface view, Layer 2 aggregate interface view, or port group view. • For IGMP snooping, configurations that you make on a Layer 2 aggregate interface do not interfere with configurations that you make on its member ports, nor do they participate in aggregation calculations. Configurations that you make on a member port of an aggregate group do not take effect until it leaves the aggregate group. Configuring basic IGMP snooping functions Before you configure basic IGMP snooping functions, complete the following tasks: • Configure the corresponding VLANs. • Determine the version of IGMP snooping. Enabling IGMP snooping Configuration guidelines • You must enable IGMP snooping globally before you enable it in a VLAN. • After you enable IGMP snooping in a VLAN, do not enable IGMP or PIM on the corresponding VLAN interface. • Wh e n yo u e nab l e I GM P s no o pi n g i n a sp e ci fie d VL A N, I GM P s no o pi n g wo rk s o nly o n t h e p o r t s i n this VLAN. Configuration procedure To enable IGMP snooping: Step Command Remarks 1. Enter system view. system-view N/A 2. Enable IGMP snooping globally and enter IGMP-snooping view. igmp-snooping Disabled by default 3. Return to system view. quit N/A 4. Enter VLAN view. vlan vlan-id N/A 5. Enable IGMP snooping in the VLAN. igmp-snooping enable Disabled by default Specifying the version of IGMP snooping Configuration guidelines Different versions of IGMP snooping can process different versions of IGMP messages: • IGMPv2 snooping can process IGMPv1 and IGMP v2 messages, but cannot process IGMPv3 messages, which will be flooded in the VLAN. • IGMPv3 snooping can process IGMPv1, IGMPv2 and IGMPv3 messages.
20 If you change I GMPv3 snooping to I GMPv2 snooping, the system clears all I GMP snooping for warding entries that are dynamically added, and also does the following: • Keeps static IGMPv3 snooping forwarding entries (*, G). • Clears static IGMPv3 snooping forwarding entries (S, G), which will be restored when IGMP snooping is switched back to IGMPv3 snooping. For more information about static joins, see Configuring static ports. Configuration procedure To specify the version of IGMP snooping: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter VLAN view. vlan vlan-id N/A 3. Specify the version of IGMP snooping. igmp-snooping version version-number Version 2 by default Configuring static multicast MAC address entries Configuration guidelines In Layer-2 multicast, a Layer 2 multicast protocol (such as, IGMP snooping) can dynamically add multicast MAC address entries. Or, you can manually configure multicast MAC address entries. In system view, the configuration is effective for the specified ports. In interface view or port group view, the configuration is effective only on the current port or the ports in the current port group. Any legal multicast MAC address except 0100-5Exx- xxxx (where x represents a hexadecimal number from 0 to F) can be manually added to the multicast MAC address table. Multicast MAC addresses are the MAC addresses whose the least significant bit of the most significant octet is 1. Configuration procedure To configure a static multicast MAC address entry in system view: Step Command Remarks 1. Enter system view. system-view N/A 2. Configure a static multicast MAC address entry. mac-address multicast mac-address interface interface-list vlan vlan-id No static multicast MAC address entries exist by default. To configure static multicast MAC address entries in interface view: Step Command Remarks 1. Enter system view. system-view N/A
21 Step Command Remarks 2. Enter Layer 2 Ethernet interface view, Layer 2 aggregate interface view, or port group view. • Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view: interface interface-type interface-number • Enter port group view: port-group manual port-group-name Use either command. 3. Configure a static multicast MAC address entry. mac-address multicast mac-address vlan vlan-id No static multicast MAC address entries exist by default. Configuring IGMP snooping port functions Configuration prerequisites Before you configure IGMP snooping port functions, complete the following tasks: • Enable IGMP snooping in the VLAN. • Configure the corresponding port groups. • Determine the aging time of dynamic router ports. • Determine the aging time of dynamic member ports. • Determine the multicast group and multicast source addresses. Setting aging timers for dynamic ports If a switch receives no IGMP general queries or PIM hello messages on a dynamic router port when the aging timer of the port expires, the switch removes the port from the router port list. If the switch receives no IGMP reports for a multicast group on a dynamic member port when the aging timer of the port expires, the switch removes the port from the multicast forwarding entry for that multicast group. If the memberships of multicast groups change freq uently, you can set a relatively small value for the aging timer of the dynamic member ports. If the memb erships of multicast groups change rarely, you can set a relatively large value. Configuring aging timers for dynamic ports globally Step Command Remarks 1. Enter system view. system-view N/A 2. Enter IGMP-snooping view. igmp-snooping N/A 3. Set the aging timer for dynamic router ports. router-aging-time interval 105 seconds by default 4. Set the aging timer for dynamic member ports. host-aging-time interval 260 seconds by default
22 Configuring aging timers for dynamic ports in a VLAN Step Command Remarks 1. Enter system view. system-view N/A 2. Enter VLAN view. vlan vlan-id N/A 3. Set the aging timer for dynamic router ports. igmp-snooping router-aging-time interval 105 seconds by default 4. Set the aging timer for dynamic member ports. igmp-snooping host-aging-time interval 260 seconds by default Configuring static ports Configuration guidelines If all hosts attached to a port are interested in th e multicast data addressed to a particular multicast group or the multicast data that a particular multicast sour ce sends to a particular group, you can configure the port as a static member port for the specified multicast group or the specified multicast source and group. You can also configure a port as a static router port, through which the switch can forward all the multicast traffic that it received. A static member port does not respond to queries fr om the IGMP querier; when you configure a port as a static member port or cancel this configuration on the port, the port does not send an unsolicited IGMP report or an IGMP leave message. Static member ports and static router ports never ag e out. To remove such a port, use the corresponding undo command. Configuration procedure To configure static ports: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter Layer 2 Ethernet interface view, Layer 2 aggregate interface view, or port group view. • Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view: interface interface-type interface-number • Enter port group view: port-group manual port-group-name Use either command. 3. Configure the port as a static member port. igmp-snooping static-group group-address [ source-ip source-address ] vlan vlan-id No static member ports exist by default. 4. Configure the port as a static router port. igmp-snooping static-router-port vlan vlan-id No static router ports exist by default.
23 Configuring a port as a simulated member host Configuration guidelines G e n e r a l l y, a h o s t t h a t r u n s I G M P c a n r e s p o n d t o I G M P q u e r i e s t h a t t h e I G M P q u e r i e r s e n d s . I f a h o s t f a i l s to respond, the multicast router might deem that no member of this multicast group exists on the network segment, and removes the corresponding forwarding path. To avoid this situation, you can configure the port as a simulated member host for a multicast group. A simulated host is equivalent to an independent host. For example, when a simulated member host receives an IGMP query, it gives a response separately. Therefore, the switch can continue receiving multicast data. A simulated host acts like a real host in the following ways: • When a port is configured as a simulated memb er host, the switch sends an unsolicited IGMP report through the port, and can respond to IGMP general queries with IGMP reports through the port. • When the simulated joining function is disabled on a port, the switch sends an IGMP leave message through the port. Unlike a static member port, a port that you conf igure as a simulated member host ages out like a dynamic member port. Configuration procedure To configure a port as a simulated member host: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter Layer 2 Ethernet interface view, Layer 2 aggregate interface view, or port group view. • Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view: interface interface-type interface-number • Enter port group view: port-group manual port-group-name Use either command. 3. Configure a port as a simulated member host. igmp-snooping host-join group-address [ source-ip source-address ] vlan vlan-id Not configured by default. Enabling fast-leave processing Configuration guidelines The fast-leave processing feature enables the switch to process IGMP leave messages quickly. With the fast-leave processing feature enabled, when the switch receives an IGMP leave message on a port, it immediately removes that port from the forwarding entry for the multicast group specified in the message. Then, when the switch receives IGMP group-specific queries for that multicast group, it does not forward them to that port. On a port that has only one host attached, you can enable fast-leave processing to save bandwidth and resources. However, on a port that has multiple hosts attached, you should not enable fast-leave
24 processing if you have enabled dropping unknown mult icast data globally or for the port. Otherwise, if a host on the port leaves a multicast group, the othe r hosts attached to the port in the same multicast group cannot receive the multicast data for the group. Configuration procedure To enable fast-leave processing globally: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter IGMP-snooping view. igmp-snooping N/A 3. Enable fast-leave processing. fast-leave [ vlan vlan-list ] Disabled by default To enable fast-leave processing for a port: Step Command Remarks 1. Enter system view. system-view N/A 2. Enter Layer 2 Ethernet interface view, Layer 2 aggregate interface view, or port group view. • Enter Layer 2 Ethernet interface view or Layer 2 aggregate interface view: interface interface-type interface-number • Enter port group view: port-group manual port-group-name Use either command. 3. Enable fast-leave processing. igmp-snooping fast-leave [ vlan vlan-list ] Disabled by default. Disabling a port from becoming a dynamic router port The following problems might exist in a multicast access network: • After receiving an IGMP general query or a PIM he llo message from a connected host, a router port becomes a dynamic router port. Before its timer expires, this dynamic router port receives all multicast packets within the VLAN where the port be longs, and forwards them to the host, affecting normal multicast reception of the host. • In addition, the IGMP general query or PIM hello message that the host sends affects the multicast routing protocol state on Layer 3 devices, such as the IGMP querier or DR election, and might further cause network interruption. To solve these problems, disable that router port from becoming a dynamic router port after the port receives an IGMP general query or a PIM hello message, so as to improve network security and control over multicast users. To disable a port from becoming a dynamic router port: Step Command Remarks 1. Enter system view. system-view N/A