Understand the context of the MAC address drift
Heroes, Xiao Bian here again! When you type the command on a device, the device at a snail's slow, and occasionally print out the alarm information MAC address drift, is not very depressed ah. Moji Moji, which Xiao Bian teach you heroes to find out the causes and effects of MAC address flapping, easy to get the most common Layer 2 network MAC address drift alarm.
First, what is the MAC address flapping it?
Drift refers to the MAC address: the same in each VLAN, MAC address has two output interfaces, and the interface to the learned overwriting an interface phenomenon. This is the official definition, popular talk, MAC address drift refers to the interface MAC address entry changes occurred. In the end what does that mean? Read the following figure to understand.
MAC address flapping What are the implications?
Ø Internet slow response! !
Ø Internet No response! !
Ø the video card can not move! !
Read these, I am not very worried Yeah, life without passion. These drifts may be a MAC address, a ring networking equipment caused. The problems for the MAC address drift, get rid of networking loop, these pesky screen will automatically disappear.
Why MAC address flapping it?
Above, under normal circumstances, PC packets entering through the Port1 Switch, will be forwarded out Port3, MAC address entries learned that the interface is Port1. However, when a loop exists between the Switch, Switch1 and Swtich2 three devices, PC's packets Switch2 -> after Switch1, Port2 will enter through the Switch, the interface resulting in an updated MAC address entry to Port2, so that it It will produce MAC address drift alarm. Layer 2 is the root cause of the loop networking drift shows that MAC address occurs.
How to determine whether there is a MAC address on the device drift it?
Ø Method 1: When the enable terminal display and an alarm switch MAC address flapping case, the MAC address is generated in the drift alarm device, alarm information will be printed out as follows. And will from time to time between multiple print yo.
Ø Method 2: when the MAC address flapping open alarm switch command to see if the cached information display trapbuffer alarm, the device determines whether there is a MAC address flapping.
Ø Method 3: When you open the MAC address flapping detection, command display mac-address flapping record to view information about the last month, MAC address drift. Information recorded includes: MAC address flapping start time and end time of the occurrence, the occurrence of VLAN and MAC address flapping MAC, and port number of drift drift.
Ø Method 4: In the absence of open MAC address flapping detection, only the most primitive way --- stop the outgoing interface MAC address entry, to determine whether there is a drift on the device MAC address. Below, multiple view MAC address entries, the hopping information of the interface between the two ports. This can be considered a MAC address drift occurs.
How to eliminate drift alarm MAC address it?
MAC address to eliminate drift in three ways:
Ø The first: the artificial drift interface shutdown.
Pros: The most simple and reliable
Disadvantages: need human intervention, the entire interface traffic will be interrupted.
The second Ø: drift detection operation by configuring the interface error-dwon, automatic drift down off the port.
Advantages: fast and timely, timing recovery ports can also be configured to automatically restore time.
Disadvantages: The entire interface traffic will be interrupted.
Third Ø: drift detection operation by configuring the interface quit-vlan, so that drift region specified VLAN exit interface, thereby eliminating drift MAC address, break the loop.
Pros: VLAN domain exists only to solve the loop, so that traffic does not interrupt other normal VLAN domain.
Cons: aging within the specified period, the only exit from one interface VLAN. If there are a plurality of loops, broken ring will be relatively slow.
MAC address of the switch to achieve drift alarm What's highlights it?
Ø Highlight 1: in the same VLAN, MAC address drift will record a record.
I.e. with each VLAN, MAC address, if there are a plurality of drift, only records a MAC address of the reported drift. why? Because as long as there is a loop VLAN domain, MAC addresses of all VLAN will take place within the drift.
Ø Highlight 2: MAC address only once or twice a drift, drift alarm will not report the MAC address.
By default, the recording aging drift in time of 300 seconds, MAC address
Entry interface to change the 10 times it considers that a MAC address drift, drift alarm will report the MAC address.
Ø Highlight 3: You can not specify a VLAN MAC address detection drift. After a specified VLAN does not detect the MAC address drift, the MAC address in the VLAN drift, does not record information, not information police report at the meeting.
Tips rivers and lakes: all MAC address flapping alarms have to deal with it? In fact, not only MAC address drift warning in case of multiple occurrences of only a short time to deal with, the occasional can not focus on it, similar to the following three cases can not concern. 1, since the loop or VRRP handover, MAC address drift caused the alarm. 2, MAC addresses of the wireless users because, drift caused the alarm. 3, because the VRRP standby switchover, MAC address drift caused the alarm.
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