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Enterasys Xpedition User Reference Manual 77

Configuring Automatic Protection Switching

When you create the point-to-point interface as shown above, the XP creates an

implicit VLAN called “SYS_L3_<interface-name>.” In the above example, the XP creates

the VLAN ‘SYS_L3_pos11.’

3. If you want to increase the MTU size on a port, specify the parameter mtu with the

‘port set’ command and define a value up to 65535 (octets). See Configuring Jumbo

Frames on page 98 for more information.

4. Specify the bit error rate thresholds, if necessary. See Specifying Bit Error Rate

Thresholds on page 79 for more information.

5. Modify any other PoS operating parameters, as needed. The following table lists the

operating parameters that you can modify and the configuration commands that you

use.

Configuring Automatic Protection Switching

Automatic protection switching (APS) provides a mechanism to support redundant

transmission circuits between SONET devices. The XP supports the following APS

features:

• Linear network topology. Ring topologies are not supported.

• 1+1 switching. Each working line is protected by one protecting line and the same

signal is transmitted on both the working and protecting lines. The two transmission

copies that arrive at the receiving end are compared, and the best copy is used. If there

is a line failure or line degradation, the end node switches the connection over to the

protecting line.

Note: In APS terminology, bridge means to transmit identical traffic on both the working

and protecting lines, while switch means to select traffic from either the protecting

line or the working line.

• Unidirectional switching, where one set of line terminating equipment (LTE) can

switch the line independent of the other LTE. Bidirectional switching (where both sets

of LTEs perform a coordinated switch) is not supported.

• Revertive switching. You can enable automatic switchover from the protecting line to

the working line after the working line becomes available.

Table 5: PoS Optional Operating Parameters

Parameter Default Value Configuration Command

Framing SONET sonet set <port> framing sdh|sonet

Loopback Disabled sonet set <port> loopback

Path tracing (none) sonet set <port> pathtrace

Circuit identifier (none) sonet set <port> circuit-id

Frame Check Sequence 32-bit sonet set <port> fcs-16-bit

Scrambling Enabled sonet set <port> no-scramble

1 2 ... 92 93 94 95 96 97 98 99 100 101 102 ... 393 394

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