No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>Search

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

S12700 V200R010C00 Configuration Guide - Ethernet Switching

This document describes the configuration of Ethernet services, including configuring link aggregation, VLANs, Voice VLAN, VLAN mapping, QinQ, GVRP, MAC table, STP/RSTP/MSTP, SEP, and so on.
Rate and give feedback:
Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Background

Background

STP prevents loops on a local area network (LAN). Switching devices running STP exchange information with one another to discover loops on the network and then block certain ports to eliminate loops. As the scale of LANs continues to grow, STP has become an increasingly important protocol.

Figure 14-1  Typical LAN networking

On the network shown in Figure 14-1, the following situations may occur:
  • Broadcast storms cause a breakdown of the network.

    If a loop exists on the network, broadcast storms may occur. In Figure 14-1, STP is not enabled on the switching devices. If Host A sends a broadcast request, both S1 and S2 receive the request on port 1 and forward the request through their port 2. Then, S1 and S2 receive the request forwarded by each other on port 2 and forward the request through port 1. As this process repeats, resources on the entire network are eventually exhausted, and the network breaks down.

  • MAC address flapping causes unstable MAC address entries.

    Even unicast packets can cause MAC address flapping on switching devices.

    HostA sends a unicast packet to HostB. If HostB is temporarily removed from the network at this time, the MAC address entry for HostB will be deleted on S1 and S2. When the unicast packet sent by HostA to HostB is received by port 1 on S1, no matching MAC address entry is found, so the unicast packet is forwarded to port 2.

    Port 2 on S2 receives the unicast packet from port 2 on S1 and sends it out through port 1. Port 1 on S2 also receives the unicast packet sent by HostA to HostB, and sends it out through port 2. These transmissions repeat and port 1 and port 2 on S1 and S2 continuously receive unicast packets from HostA. S1 and S2 modify their MAC address entries each time, causing the MAC address table to flap. As a result, MAC address entries are unstable.

Translation
Download
Updated: 2019-08-21

Document ID: EDOC1000142081

Views: 273770

Downloads: 420

Average rating:
This Document Applies to these Products
Related Version
Related Documents
Share
Previous Next