Login
- Table of Contents
-
- H3C WX3000 Series Unified Switches Switching Engine Configuration Guide-6W103
- 00-Preface
- 01-CLI Configuration
- 02-Login Configuration
- 03-Configuration File Management Configuration
- 04-VLAN Configuration
- 05-Auto Detect Configuration
- 06-Voice VLAN Configuration
- 07-GVRP Configuration
- 08-Basic Port Configuration
- 09-Link Aggregation Configuration
- 10-Port Isolation Configuration
- 11-Port Security-Port Binding Configuration
- 12-DLDP Configuration
- 13-MAC Address Table Management Configuration
- 14-MSTP Configuration
- 15-802.1x and System Guard Configuration
- 16-AAA Configuration
- 17-MAC Address Authentication Configuration
- 18-IP Address and Performance Configuration
- 19-DHCP Configuration
- 20-ACL Configuration
- 21-QoS-QoS Profile Configuration
- 22-Mirroring Configuration
- 23-ARP Configuration
- 24-SNMP-RMON Configuration
- 25-Multicast Configuration
- 26-NTP Configuration
- 27-SSH Configuration
- 28-File System Management Configuration
- 29-FTP-SFTP-TFTP Configuration
- 30-Information Center Configuration
- 31-System Maintenance and Debugging Configuration
- 32-VLAN-VPN Configuration
- 33-HWPing Configuration
- 34-DNS Configuration
- 35-Smart Link-Monitor Link Configuration
- 36-PoE-PoE Profile Configuration
- 37-Routing Protocol Configuration
- 38-UDP Helper Configuration
- 39-Acronyms
- 40-Index
- Related Documents
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| Title | Size | Download |
|---|---|---|
| 12-DLDP Configuration | 67.12 KB |
l The term switch used throughout this chapter refers to a switching device in a generic sense or the switching engine of a unified switch in the WX3000 series.
l The sample output information in this manual was created on the WX3024. The output information on your device may vary.
DLDP Overview
You may have encountered unidirectional links in networking, as shown in Figure 1-1 and Figure 1-2. When a unidirectional link occurs, the local device can receive packets from the peer device through the link layer, but the peer device cannot receive packets from the local device. Unidirectional links can cause many problems, such as spanning tree topology loop.
Device Link Detection Protocol (DLDP) can detect the link status of the optical fiber cable or copper twisted pair (such as super category 5 twisted pair). If DLDP finds a unidirectional link, it disables the related ports automatically or informs users to disable them manually according to the configurations, to avoid network problems.
Figure 1-1 Fiber cross-connection
Figure 1-2 Fiber correct connection/disconnection in one direction
DLDP provides the following features:
l As a link layer protocol, it works together with the physical layer protocols to monitor the link status of a device. While the auto-negotiation mechanism on the physical layer detects physical signals and faults; DLDP identifies peer devices and unidirectional links, and disables unreachable ports.
l Even if the links of both ends can normally operate individually on the physical layer, DLDP can detect (at the link layer) whether these links are connected correctly and packets can be exchanged normally between the two ends. This detection cannot be implemented by the auto-negotiation mechanism.
l When the port works in mandatory full duplex mode and the mandatory rate, DLDP can detect fiber disconnection in one direction as shown in Figure 1-2.
l When the port works in auto-negotiation duplex mode and auto-negotiation rate, even if DLDP is enabled, it does not take effect when fiber in one direction is disconnected as shown in Figure 1-2, in that case, it considers that the port is down.
DLDP Fundamentals
DLDP status
A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe, disable, and delaydown.
|
Status |
Description |
|
Initial |
DLDP is not enabled. |
|
Inactive |
DLDP is enabled but the corresponding link is down |
|
Active |
DLDP is enabled and the link is up, or an neighbor entry is cleared |
|
Advertisement |
All neighbors communicate normally in both direction, or DLDP remains in active status for more than five seconds and enters this status. It is a stable status when no unidirectional link is found |
|
Probe |
DHCP sends packets to check if it is a unidirectional link. It enables the probe sending timer and an echo waiting timer for each target neighbor. |
|
Disable |
DLDP detects a unidirectional link, or finds (in enhanced mode) that a neighbor disappears. In this case, DLDP does not receive or send DLDP packets. |
|
Delaydown |
When a device in the active, advertisement, or probe DLDP state receives a port down message, it does not removes the corresponding neighbor immediately, neither does it changes to the inactive state. Instead, it changes to the delaydown state first. When a device changes to the delaydown state, the related DLDP neighbor information remains, and the Delaydown timer is triggered. |
DLDP timers
DLDP works with the following timers:
|
Timer |
Description |
|
Advertisement sending timer |
Interval of sending advertisement packets, which can be configured with a command line. By default, the interval is 5 seconds. |
|
Probe sending timer |
The interval is 0.5 second. In probe status, DLDP sends two probe packets every second. |
|
Echo waiting timer |
It is enabled when DLDP enters probe status. The timeout time is 10 seconds. If no echo packet is received from the neighbor when the Echo waiting timer expires, the local end is set to unidirectional communication status and the state machine turns into disable status. DLDP outputs log and tracking information, sends flush packets. Depending on the user-defined DLDP down mode, DLDP disables the local port automatically or prompt the user to disable the port manually. At the same time, DLDP deletes the neighbor entry. |
|
Entry aging timer |
When a new neighbor joins, a neighbor entry is created, and the corresponding entry aging timer is enabled. When an advertisement packet is received from a neighbor, the neighbor entry is updated, and the corresponding entry aging timer is updated. In normal mode, if no packet is received from the neighbor when the entry aging timer expires, DLDP sends an advertisement packet with RSY tag, and deletes the neighbor entry. In enhanced mode, if no packet is received from the neighbor when the entry aging timer expires, DLDP enables the enhanced timer. The interval set for the entry aging timer is three times of that for the advertisement timer. |
|
Enhanced timer |
In enhanced mode, if no packet is received from the neighbor when the entry aging timer expires, DLDP enables the enhanced timer for the neighbor. The timeout time for the enhanced timer is 10 seconds. The enhanced timer then sends one probe packets every one second and totally eight packets continuously to the neighbor. If no echo packet is received from the neighbor when the Enhanced timer expires, the local end is set to unidirectional communication status and the state machine turns into disable status. DLDP outputs log and tracking information, and sends flush packets. Depending on the user-defined DLDP down mode, DLDP disables the local port automatically or prompt the user to disable the port manually. DLDP deletes the neighbor entry. |
|
Delaydown timer |
When a device in the active, advertisement, or probe DLDP state receives a port down message, it does not removes the corresponding neighbor immediately, neither does it changes to the inactive state. Instead, it changes to the delaydown state first. When a device changes to the delaydown state, the related DLDP neighbor information remains, and the Delaydown timer is triggered. The Delaydown timer is configurable and ranges from 1 to 5 seconds. A device in the delaydown state only responds to port up messages. A device in the delaydown state resumes its original DLDP state if it receives a port up message before the delaydown timer expires. Otherwise, it removes the DLDP neighbor information and changes to the inactive state. |
DLDP operating mode
DLDP can operate in two modes: normal and enhanced.
Table 1-3 DLDP operating mode and neighbor entry aging
|
DLDP operating mode |
Whether DLDP probes neighbor during neighbor entry aging |
Whether entry aging timer is enabled during neighbor entry aging |
Whether enhanced timer is enabled when entry aging timer expire |
|
Normal mode |
No |
Yes (the neighbor entry ages after the entry aging timer expires) |
No |
|
Enhanced mode |
Yes |
Yes (the enhanced timer is enabled after the entry aging timer expires) |
Yes (When the enhanced timer expires, the local end is set to single pass status, and the neighbor entry ages) |
DLDP implementation
1) If the DLDP-enabled link is up, DLDP sends DLDP packets to the peer device, and analyses and processes DLDP packets received from the peer device. DLDP in different status sends different packets.
Table 1-4 Types of packets sent by DLDP
|
DLDP status |
Packet types |
|
Active |
Advertisement packets, including those with or without RSY tags |
|
Advertisement |
Advertisement packets |
|
Probe |
Probe packets |
2) DLDP analyzes and processes received packets as follows:
l In authentication mode, DLDP authenticates the packets, and discards those do not pass the authentication.
l DLDP processes the received DLDP packets.
Table 1-5 Process received DLDP packets
|
Packet type |
Processing procedure |
||||
|
Advertisement packet |
Extract neighbor information |
If this neighbor entry does not exist on the local device, DLDP creates the neighbor entry, enables the entry aging timer, and turns to probe status. |
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|
If the neighbor entry already exists on the local device, DLDP refreshes the entry aging timer. |
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|
Flush packet |
Delete the neighbor entry from the local device |
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|
Probe packet |
Send echo packets containing both neighbor and its own information to the peer |
Create the neighbor entry if this neighbor entry does not exist on the local device. |
|||
|
If the neighbor entry already exists on the local device, refresh the entry aging timer. |
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|
Echo packet |
Check whether the local device is in probe status |
No |
Discard this echo packet |
||
|
Yes |
Check whether neighbor information in the packet is the same as that on the local device |
No |
Discard this echo packet |
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|
Yes |
Set the neighbor flag bit to bidirectional |
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|
If all neighbors are in bidirectional communication state, DLDP turns from probe status to advertisement status, and sets the echo waiting timer to 0. |
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3) If no echo packet is received from the neighbor, DLDP performs the following processing:
Table 1-6 Processing when no echo packet is received from the neighbor
|
No Echo packet received from the neighbor |
Processing procedure |
|
In normal mode, no echo packet is received when the echo waiting timer expires |
DLDP turns into disable status. It outputs log and tracking information, sends flush packets. Depending on the user-defined DLDP down mode, DLDP disables the local port automatically or prompt the user to disable the port manually. DLDP sends the RSY message and deletes the neighbor entry. |
|
In enhanced mode, no echo packet is received when the enhanced timer expires |
DLDP neighbor state
A DLDP neighbor can be in one of these two states: two way and unknown. You can check the state of a DLDP neighbor by using the display dldp command.
Table 1-7 Description on the two DLDP neighbor states
|
DLDP neighbor state |
Description |
|
two way |
The link to the neighbor operates properly. |
|
unknown |
The device is detecting the neighbor and the neighbor state is unknown. |
Precautions During DLDP Configuration
l DLDP works only when the link is up.
l To insure unidirectional links can be detected, you must make sure: DLDP is enabled on both ends, and the interval of sending advertisement packets, authentication mode and password are consistent on both ends.
l You can adjust the interval of sending advertisement packets in different network circumstances, so that DLDP can respond rapidly to link failure. The interval must be shorter than one-third of the STP convergence time, which is generally 30 seconds. If too long an interval is set, an STP loop may occur before DLDP shut down unidirectional links. On the contrary, if too short an interval is set, network traffic increases, and port bandwidth is reduced.
l DLDP does not process any LACP event, and treats each link in the aggregation group as independent.
DLDP Configuration
DLDP Configuration Tasks
Follow these steps to configure DLDP:
|
Use the command… |
Remarks |
|||
|
Enter system view |
system-view |
— |
||
|
Enable DLDP |
Enable DLDP globally |
dldp enable |
Required. By default, DLDP is disabled |
|
|
Enable DLDP on a port |
Enter Ethernet port view |
Interface interface-type interface-number |
||
|
Enable DLDP on a port |
dldp enable |
|||
|
Set the authentication mode and password |
dldp authentication-mode { none | simple simple-password | md5 md5-password } |
Optional. By default, the authentication mode is none |
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|
Set the interval of sending DLDP packets |
dldp interval integer |
Optional. By default, the interval is 5 seconds. |
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|
Set the delaydown timer |
dldp delaydown-timer delaydown-time |
Optional By default, the delaydown timer expires after 1 second it is triggered. |
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|
Set the DLDP handling mode when an unidirectional link is detected |
dldp unidirectional-shutdown { auto | manual } |
Optional. By default, the handling mode is auto. |
||
|
Set the DLDP operating mode |
dldp work-mode { enhance | normal } |
Optional. By default, DLDP works in normal mode. |
||
|
Enter Ethernet port view |
interface interface-type interface-number |
— |
||
|
Display the configuration information about the DLDP-enabled ports |
display dldp { unit-id | interface-type interface-number } |
You can execute this command in any view. |
||
l When you use the dldp enable/dldp disable command in system view to enable/disable DLDP globally on all optical ports of the device, this command is only valid for existing optical ports on the device, however, it is not valid for those added subsequently.
l DLDP can operate normally only when the same authentication mode and password are set for local and peer ports.
Resetting DLDP Status
The command here is only valid for those ports that are DLDP down due to the detection of unidirectional link. You can use the command here to reset the DLDP status of these ports to retrieve DLDP probes.
Follow these steps to reset DLDP status:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
Optional |
|
Reset the DLDP status of the system |
dldp reset |
|
|
Enter Ethernet port view |
interface interface-type interface-number |
|
|
Reset the DLDP status of a port |
dldp reset |
This command only applies to the ports in DLDP down status.
DLDP Network Example
Network requirements
As shown in Figure 1-3:
l Switch A and Switch B are connected through two pairs of fibers. Both of them support DLDP;
l Suppose the fibers between Switch A and Switch B are connected inversely. DLDP disconnects the unidirectional links after discovering them;
l When the network administrator connects the fiber correctly, the ports taken down by DLDP are restored.
Figure 1-3 Fiber cross-connection
Configuration procedure
1) Configure Switch A
# Configure the ports to work in mandatory full duplex mode at the speed of 1000 Mbps.
<SwitchA> system-view
[SwitchA] interface gigabitethernet 1/0/10
[SwitchA-GigabitEthernet1/0/10] duplex full
[SwitchA-GigabitEthernet1/0/10] speed 1000
[SwitchA-GigabitEthernet1/0/10] quit
[SwitchA] interface gigabitethernet 1/0/11
[SwitchA-GigabitEthernet1/0/11] duplex full
[SwitchA-GigabitEthernet1/0/11] speed 1000
[SwitchA-GigabitEthernet1/0/11] quit
# Enable DLDP globally
[SwitchA] dldp enable
DLDP is enabled on all fiber ports except fabric ports.
# Set the interval of sending DLDP packets to 15 seconds
[SwitchA] dldp interval 15
# Configure DLDP to work in enhanced mode
[SwitchA] dldp work-mode enhance
# Set the DLDP handling mode for unidirectional links to auto
[SwitchA] dldp unidirectional-shutdown auto
# Display the DLDP status
[SwitchA] display dldp 1
When two switches are connected through fibers in a crossed way, two or three ports may be in the disable state, and the rest in the inactive state.
When a fiber is connected to a device correctly on one end with the other end connected to no device:
l If the device operates in the normal DLDP mode, the end that receives optical signals is in the advertisement state; the other end is in the inactive state.
l If the device operates in the enhance DLDP mode, the end that receives optical signals is in the disable state; the other end is in the inactive state.
# Restore the ports taken down by DLDP
[SwitchA] dldp reset
2) Configure Switch B
The configuration of Switch B is the same to that of Switch A.
