VRRP heartbeat packet transmission for S series switches

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For S series switches (S1700 excluded), in a VRRP + STP scenario, a VRRP group is configured on SwitchA and SwitchB. If the switch connected to a user cannot forward VRRP packets (for example, discarding unknown multicast packets is configured), or to prevent the link disconnectivity or instability for VRRP packets (heartbeat packets), a heartbeat line can be deployed between SwitchA and SwitchB to transmit VRRP packets.

Other related questions:
Can VRRP heartbeat packets of an AR router be transmitted on Layer 2 only
Can VRRP heartbeat packets of an AR router be transmitted on Layer 2 only? The answer is Yes. At present, VRRP heartbeat packets cannot be forwarded on Layer 3, therefore VRRP advertisement packets cannot be transmitted transparently on the Layer 3 interface of the AR router as well.

Why VRRP heartbeat packets cannot be transmitted normally between VRRP master and backup devices when VRRP packets are sent in a Super-VLAN
For S series switches, by default, VRRP Advertisement packets of a super-VLAN are sent only to the sub-VLAN that has the smallest VLAN ID among all the sub-VLANs in Up state. VRRP heartbeat packets cannot be transmitted normally between VRRP master and backup devices when the link between them does not allow the first Sub-VLAN of the Super-VLAN. The vrrp advertise send-mode command can be used to cancel or configure the mode in which VRRP Advertisement packets of a super-VLAN are sent.

How do I configure MSTP and VRRP on an S series switch
An S series switch (except the S1700) connected to user terminals cannot forward VRRP packets (because discarding unknown multicast packets is configured, for example), or the links that VRRP packets (heartbeat packets) pass through are faulty or unstable. To address such problems, configure a heartbeat line between two switches to transmit VRRP packets. Loops may occur between the two switches after the heartbeat line is configured. Therefore, you need to configure a loop prevention protocol such as STP or MSTP to prevent loops. For details on how to configure VRRP and MSTP, see topic Example for Configuring MSTP and VRRP in section "Typical Examples of MSTP/RRPP/SEP/VBST" at S1720&S2700&S3700&S5700&S6700&S7700&S9700 Typical Configuration Examples. The configuration method for the S9300 is the same as that for other switch models. When configuring VRRP on a switch separately, STP does not need to be disabled.

Layer 2 transparent transmission mechanism for 802.1x protocol packets on S series switches
For S series switches (except the S1700), the Layer 2 transparent transmission mechanism for 802.1 protocol packets is as follows: 1. When an 802.1x protocol packet reaches the ingress node, the switch changes the multicast destination MAC address of the packet to a specified multicast MAC address. 2. After the MAC address of an 802.1x protocol packet is changed, the switch does not send the packet to the CPU for processing but directly forwards the packet on the Layer 2 network based on the configuration. 3. When the 802.1x protocol packet reaches the egress node, the switch restores the multicast destination MAC address of the packet to the standard multicast destination MAC address based on the mapping between the specified multicast destination MAC address and the 802.1x protocol configured on the switch.

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