The full sub-ring is not being formed in order to have one RPL in sub-ring. The major rings are woking the RPLs are configured for both rings.

In this scenario we assume we are aware of configuring the basic ERPS configuration.

The intersecting switch Nodes (LSW 3 - 4 - 5 - 6) , are configured in order to create Major rings and Sub-rings, see below configuration:

stp region-configuration<?xml:namespace prefix = "o" />

instance 1 vlan 1 to 4093

active region-configuration             

#

erps ring 1

control-vlan 4080

protected-instance 1

version v2

#

erps ring 2

control-vlan 4081

protected-instance 1

sub-ring

version v2

 See below network topology for further understanding.

Sub-ring is wanted to be formed between LSW 3 - 4 - 5 - 6, but from some cause is no being formed, the cause why is not being formed is because R-APS PDUs are not being exchanged between all the Sub-ring Nodes, this will result in not being able to set the RPL for the Sub-ring.

        -The R-APS PDUs sent by LSW3 can't reach LSW4, same behavior from LSW4 side.

        -The R-APS PDUs sent by LSW5 can't reach LSW6, same behavior from LSW6 side.

        -The R-APS PDUs can be exchanged on the Link between LSW3 <->LSW5,  same behavior for the Link between LSW4 <-> LSW6.

Siwtches LSW 3 - 4 - 5 - 6 are the intersecting Nodes of the rings, Major and Sub-ring rings, these we result in Common links: 

        -Major ring 1 and Sub-ring will have the common link between LSW3 - LSW4 (GE 0/0/2 - Ge0/0/2)

        -Major ring 2 and Sub-ring will have the common link between LSW5 - LSW6 (GE0/0/2 - GE0/0/2)

By default the Common links are appart from Major Rings.