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Unable to local access (using WebLCT) to RTN when link is UP due to different subnet mask length setting with gateway (subnet mask), able to local access only when the link is DOWN

Publication Date:  2012-07-25 Views:  175 Downloads:  0

Issue Description

Problem happened at RTN site, able to login the RTN950 when the link have not UP and running, BUT when the link is UP and running, not able to local access to the RTN950

Alarm Information


Handling Process

  1. Reboot the RTN we’re able to ping and to log in for approximately 40sec, and then the connection is cut.
  2. Shut down the radio-link, we are able to reconnect to the RTN and we do not lose the connection anymore.
  3. Tried this with two different laptops (when radio-link is UP), problem persists.
  4. Discovered that the problem RTNs have been configured with subnet mask of and the gateway RTN subnet mask is
  5. This meant that RTNs with problem are having subnet mask length of 27 and gateway RTN is having subnet mask length of 29.
  6. Once change the problem RTNs with same subnet mask length as gateway RTN-, turn up radio-link UP, local access to this RTNs with no problem anymore.
Please refer to attached files for detail explanation and understanding.

Root Cause

When broadcast packets are transmitted for NE search, the PC transmits packets that carry the IP address of and MAC address of all "f"s. After receiving the packets, NE1 forwards the packets to NE2, because a route of the subnet with a 24-bit subnet mask targets NE2.
After receiving the packets,  NE2 unicasts the packets to the PC. That is, communication is normal in this case.
When multicast packets are transmitted for NE search, NE1 can receive the packets sent by the PC but does not forward the packets. In this case, you can find NE1 by using the Navigator.
The Web LCT does not support the packet multicast function. Therefore, you can find only NE1 by using the Web LCT.


Set the RTN subnet mask to to be same as gateway RTN.

Hope this helpful for engineers face similar problem !
Thank you.