Configuring IS-IS fast convergence on S series switches


To configure IS-IS fast convergence on S series switches supporting IS-IS, run the following commands in the IS-IS process:
timer spf
timer lsp-generation

Other related questions:
Whether the S-series switches support fast forwarding

How does RSTP implement P/A fast convergence
RSTP implements fast convergence by improving the STP protocol. The link is point-to-point, and RSTP changes to the forwarding state based on the P/A fast convergence: The upstream device sends the Proposal packet and starts the waiting timer. The downstream device blocks all other ports and sends back the Agreement packet to the upstream device. The upstream device receives the Agreement packet and the port enters the forwarding state. The preceding process is repeated between all upstream devices and downstream devices, implementing the fast convergence on the entire RSTP network. NOTE: The P/A fast convergence cannot be implemented for non-point-to-point links. If a Huawei device is connected to a device from other manufacturers, run the stp no-agreement check command to implement fast convergence.

Configure an S series switch to accelerate OSPF route convergence
The following network changes affect OSPF route convergence. A device detects that the peer link is down and the neighbor relationship becomes invalid. A new link-state advertisement (LSA) is generated and flooded. The Link State Database (LSDB) is updated. A new route is calculated through the Shortest Path First (SPF) routing algorithm and delivered to the Forwarding Information Base (FIB) table. To accelerate OSPF aggregation, you can perform the following operations on a switch: Set a Hello interval and a Dead interval on the peer device or configure the BFD to rapidly detect failures. Set spf-schedule-interval (of which the default value is 5, in seconds) to a smaller value to shorten the SPF calculation interval. Set the LSA generation interval to a smaller value. Set the LSA arrival check interval to a smaller value. Run the ospf trans-delay command in an interface view to speed up LSA flooding.

How is convergence performance of Layer 2 multicast accelerated on an S series switch?
When the network topology changes, Layer 2 multicast detects the topology change by responding to notification messages of ring network protocols. Layer 2 multicast sends General Query messages in the VLAN where the topology changes to re-collect group member relationships. Ring network protocols include STP, MSTP, RRPP, Smart Link, and SEP. The ring network protocols supported by the switches excluding the S1700 are as follows: - STP: supported by all switch models - MSTP: supported by all switch models excluding the S2700SI - RRPP: supported by all switch models excluding the S1720 and S2700SI - Smart Link: supported by all switch models excluding the S1720, S2700SI, S2710SI, and S2700EI - SEP: supported by all switch models excluding the S1720, S2700SI, S2710SI, and S2700EI

Implementation and application of fast leave of S series switches
For an S series switch, the fast leave function is configured using the igmp-snooping prompt-leave command (for Layer 2 multicast) or the igmp prompt-leave command (for Layer 3 multicast). If this function is not configured, the switch sends a Group-Specific Query message in response to an IGMP Leave message to check whether there are other users in the group specified in the Leave message. After fast leave is configured, the switch directly deletes the interface that receives the IGMP Leave message from the multicast forwarding entry, and does not check whether there are still users in the group. The fast leave function is applicable only to interfaces with only one user attached. If fast leave is configured on an interface connecting to multiple users, multicast traffic of all users under the interface is interrupted when one user switches to another channel.

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