No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

The PCU and the SGSN Fail to Communicate with Each Other Because No Static Route Is Configured on the NE40E

Publication Date:  2012-07-27 Views:  36 Downloads:  0
Issue Description
The SGSN needs to communicate with the BSC PCU through an MPLS bearer network. After corresponding configurations are complete, the PCU cannot communicate with the SGSN. Each PE device can ping through the gateway address of the PCU, but cannot ping through the physical address of the PCU. The local PE, however, can ping through the physical address of the PCU.
The network topology is shown as follows:
SGSN��S3928P��NE40E��MPLS network��NE40E��PCU
Version information: NE40E V300R003C02B382 PH003 patch 
Alarm Information
Null
Handling Process
1. Replace the PCU with a PC whose IP address is a physical address of the PCU and whose gateway is a VRRP virtual address. The PC can be successfully pinged by the SGSN and remote routers PE1 and PE2.
2. Use the PCU for testing. The problem still exists. Check the PCU and you can find that in addition to the physical IP address, a logical IP address belonging to on another network segment exists.
3. On the PE1 or PE2, create a static route to the logical address of the PCU with the physical address of the PCU as the next hop. Test the connectivity between the PCU and PE1 or PE2, and you can find that the problem is solved.
4. The route configured on the PCU has the IP address of the SGSN as the destination address and the VRRP virtual address of the local router as the next hop. The IP address of the remote router is unreachable for the PCU. Therefore, the PCU and the remote router cannot ping through each other even if the SGSN and PCU can successfully ping each other. 
Root Cause
1. The SGSN can communicate with other devices normally. Therefore, the problem occurs on the PCU side.
2. The PCU is a wireless device configured with two IP addresses, which belonging to different network segments. One is the IP address of a physical interface, whereas the other is the logical address used by the PCU.
3. The PCU uses the logical IP address as the source address to communicate with the SGSN. Because no routes to the network segment where the logical IP address resides are configured on the PE side, the PCU cannot communicate with the SGSN normally.
4. Remote PEs cannot ping through the physical interface of the PCU because that no corresponding backhaul routes are configured on the PCU. The route configured on the PCU is not a default route, but a route to the network segment where the IP address of the SGSN resides. As a result, remote PEs cannot ping through the PCU. 
Suggestions
The PCU uses a logical address as the source address for communication, and thus you need to consider the route to the network segment where the logical IP address resides. To allow the remote device to communicate with the PCU, you need to configure an interface with the IP address belonging to the same network segment as the SGSN. After that, you can ping the specific source address. 

END