2 BTS failed after wrong VC12 in EOS
Hi ,
Dear Community , today I have a case related of a wrong VC12 configuration in EOS caused 2 BTS service failure .
Description
- we were doing an expansion for the EOS service of 1*BTS for the mobile 2G service provider , the link was composed of a series of OSN equipment in liner network .
an OSN-7500 connected with the BSC by 1Gb port ( EGS4 Board ) then OSN-500 provides Ethernet in the site of BTS no. 1 and another OSN-500 also provides Ethernet in the site of BTS 2.
-The LCAS feature is enabled and every BTS is differentiated by VLAN . BTS no. 1 configured with VC-TRUNK no. 1 and BTS no. 2 configured with VC-TRUNK no. 2 .
-Directly after expansion of the Ethernet service of BTS no. 1 , both BTSs got out of service , there were no alarm , but we got a call of the client ( the Mobile service provider ) claiming that the service in these 2 sites is down.
Network diagram
-The problem cause
-we started troubleshooting with checking LCAS setting , but it was enabled , then we checked the configuration as the problem happened after the expansion of the service speed , we found that 1 * VC-12 configured to VC-TRUNK 1 in the OSN-7500 cross-connected mistakenly to BTS . No 2 instead of BTS no.1 .
-The conclusion & solution
As EOS uses GFP to map variable length Ethernet payload to synchronous transport paths , the GFP frames contain all signal information like MAC and VLAN and pack them as one package.
Transparent Generic Framing Procedure (GFP) | EE Times
- When mistakenly crossed the VC-12 between the two BTS , the information of MAC and VLAN conflicted in the BTS no. 1 and in the BSC causing the BTSs both in site 1 and in site 2 to fail .
- After correcting the cross connection of the VC12 and dropping it in site no. 1 , to BTS no. 1 , everything went well and problem solved .
Welcome to comment and feedback
