1 2007 D-Link Switch Training ©Copyright 2007. By D-Link HQ TSD James Chu.

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2007 D-Link Switch Training ©Copyright 2007. By D-Link HQ TSD James Chu

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Loop Back Detection (LBD) Overview

What’s difference between port-Base LBD and VLAN-Base LBD

Hands-on

Agenda

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Loop Back Detection Overview LBD4.0 is a new version Loopback Detection algorithm which will be implement

ed in DES-3500 R5

The main differences between STP loopback detection (LBD2.0) and latest LBD (LBD 4.0) function

1. STP independent

For LBD2.0 – the STP loopback detection uses BPDU as to detect the loop, it's necessary to enable the STP to make lbd feature work.

For LBD 4.0 – we use another packet (Multicast) type to detect the loop, and we think that this is a better solution than the " STP - dependent " one.

2. Options for action when the loop occurs:

Action 1: shut down the port Action 2: shut down the individual vlan with loop

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Loop Back Detection Overview

The idea comes from telecom customer's request. If the port belongs to multiple vlan and it's shut down by lbd because of loop happening in one of the vlans, then all the other vlan members / devices underneath that port will be impacted. In order to prevent such impact, we provide two selectable actions for users:

1. Block the traffic from the loop happening vlan without port shut down. The benifit is, there won't influence to those devices or members of other vlans because the

port won't be shut down. The side effect is, since the port is not shut down, the CPU may still receive the traffic incl

uding BPDU or ARP/broadcast packets to cause its high loading. Then we'll need to enable safeguard engine for help to protect the CPU.

2. Port shut down ( as the default ) it's completely the same behavior as the original one.

v1 v2 v3

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Loop Back Detection Overview

It will send in every 10 secs to a multicast address:(cf:00:00:00:00:00) by default to see if a same packet receive on a originated interface.

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DES-3526

Port Base LBD Example

If the switch get the multicast packet sent from itself from the port which would be blocked by switch.

Port Base LBD Example

HUB/Switch

Command Example

enable loopdetect

config loopdetect ports 1-26 state enabled

config loopdetect mode port-based

Port 1

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DES-3526:admin#show loopdetect Command: show loopdetect

Loopdetect Global Settings --------------------------- Loopdetect Status : Enabled Loopdetect Interval : 10 Recover Time : 60 Mode : Port-Based

Success.

DES-3526:admin#

DES-3526:admin#show loopdetect ports all Command: show loopdetect ports all

Port Loopdetect State Loop Status------ ------------------ ----------1 Enabled Loop!1 Enabled Normal 2 Enabled Normal 3 Enabled Normal 4 Enabled Normal 5 Enabled Normal 6 Enabled Normal 7 Enabled Normal 8 Enabled Normal 9 …………………………..

How to verify Loop Back Detection (Port-Base) command

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DES-3526:admin#show ports Command: show portsPort Port Settings Connection Address Trap State Speed/Duplex/FlowCtrl Speed/Duplex/FlowCtrl Learning State---- -------- --------------------- --------------------- -------- --------1 Disabled Auto/Disabled Link Down Enabled Enabled 2 Enabled Auto/Disabled Link Down Enabled Enabled 3 Enabled Auto/Disabled Link Down Enabled Enabled 4 Enabled Auto/Disabled Link Down Enabled Enabled 5 Enabled Auto/Disabled Link Down Enabled Enabled 6 Enabled Auto/Disabled Link Down Enabled Enabled 7 Enabled Auto/Disabled Link Down Enabled Enabled 8 Enabled Auto/Disabled Link Down Enabled Enabled 9 Enabled Auto/Disabled Link Down Enabled Enabled 10 Enabled Auto/Disabled Link Down Enabled Enabled 11 Enabled Auto/Disabled Link Down Enabled Enabled 12 Enabled Auto/Disabled Link Down Enabled Enabled 13 Enabled Auto/Disabled Link Down Enabled Enabled 14 Enabled Auto/Disabled Link Down Enabled Enabled 15 Enabled Auto/Disabled Link Down Enabled Enabled 16 Enabled Auto/Disabled Link Down Enabled Enabled

How to verify Loop Back Detection (Port-Base) command

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DES-3526-2

VLAN Base LBD Example

If the switch get the multicast packet sent from port 26, it will block all traffic from the VLAN 1 of DES-3526-2

VLAN Base LBD Example

HUB/Switch

V1Port 1-8, 26 Tag port 26

Tag port 26

DES-3526-1

V2Port 9-16,26

V3Port 17-26

V1Port 1-8, 26

V2Port 9-16,26

V3Port 17-26Port 1

Port 8

Port 23

Port 23

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2. Loop Back Detection Configuration (VLAN-Base) Example

create vlan v2 tag 2 create vlan v3 tag 3config vlan default delete 8-26config vlan default add tagged 25-26config vlan v2 add untagged 9-16config vlan v2 add tagged 25-26config vlan v3 add untagged 17-26 config vlan v3 add tagged 25-26

enable loopdetect config loopdetect mode vlan-based config loopdetect ports 1-26 state enabled

Loop Back Detection Configuration (VLAN-Base) Example

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DES-3526:admin#show loopdetect ports all Command: show loopdetect ports all

Port Loopdetect State Loop VLAN------ ------------------ ----------22 Enabled None 23 Enabled None 24 Enabled None 25 Enabled None 26 Enabled 1

DES-3526:admin#show ports Command: show portsPort Port Settings Connection Address Trap State Speed/Duplex/ FlowCtrl Speed/Duplex/FlowCtrl Learning State---- -------- --------------------- --------------------- -------- --------21 Enabled Auto/Disabled Link Down Enabled Enabled 22 Enabled Auto/Disabled Link Down Enabled Enabled 23 Enabled Auto/Disabled 100M/Full/None Enabled Enabled 24 Enabled Auto/Disabled Link Down Enabled Enabled 25 Enabled Auto/Disabled Link Down Enabled Enabled 26 Enabled Auto/Disabled Err-Disabled Enabled Enabled

DES-3526:admin#show ports err_disabled Command: show ports err_disabledPort Port Connection status Reason State------ -------- --------------------- ----------------26 Enabled Err-Disabled Loopdetect Description:

DES-3526:admin#

How to verify Loop Back Detection (VLAN-Base) command

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Loop Back Detection Test ResultLoop Back Detection Test Result

Test Result:

1. For port base LBD, the switch will block the port which receive the loopback multicast packet sent from itself.

2. For VLAN base LBD, the switch will block the VLAN traffic when the switch receives the loopback multicast packet sent from itself from that VLAN.

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