Udld Configuration; Udld Overview - Zte ZXR10 5900 Series User Manual

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C h a p t e r

UDLD Configuration

Table of Contents

UDLD Overview ............................................................... 105

Configuring UDLD ............................................................ 106
UDLD Overview
UDLD is a layer 2 logic link detection protocol. It can detect Eth-
ernet link logic connectivity and verify physical connectivity. Dif-
ferent from physical connection detection, UDLD detects based on
neighbor. The layer 1 device is transparent to UDLD.
UDLD detection builds up neighbor relationship with adjacent layer
2 devices firstly. When the Ethernet port whose status is UP opens
UDLD function, this port sends Hello packet that neighbor has en-
tered to inform other adjacent related devices. The adjacent re-
lated devices port that opens UDLD function receives this Hello
packet and sends an Echo packet back. From the point of view of
this device, that receiving this Echo packet means that the two de-
vices are interconnection and the neighbor relationship with peer
device has established on this device and sends Echo packet back.
After the peer receiving Echo packet, the relationship on the two
devices is established.
After both sides establish the neighbor relationship, send detection
Hello packet at regular time to detect if the detection link works
normally. When receiving the Hello detection packet sent from
neighbor, update local storage neighbor buffer information and re-
set neighbor outtime. If exceed neighbor aging time and still not
receiving Hello detection packet, consider that link is on abnormal
working condition and need different working modes to handle.
UDLD has two working modes: ordinary mode and aggressive
mode. In ordinary mode, only when packets are received and
link is verified to be through in uni-direction, this interface can be
down; in case corresponding packets are not received or link fails
to be verified through in uni-direction, this operation will not be
conducted on the interface; In aggressive mode, as long that link
fails to be verified to be through bidirectionally, the interface will
be down. The common point of the two modes is that in any cir-
cumstance, as long as the link is not verified to work normally ,
print alarm.
Generally speaking, there are several conditions that UDLD sets
interface down.
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