Download - Rac Lac Lookups
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PS RAC/LAC Lookups
Dave Stokes
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3G SGSN config > RAN Association
Once logged in to the pageTake a note of the LAC and RAC
Numbers in decimalFor this example 58 and 58
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Convert the Dec values into Hex
• Using you calculator convert the decimal values into Hex RAC=58 and LAC=58
• 58 = 3A in Hex and obviously this is the same for the LAC also but they are not always the same value so check.
• The SGSN needs 4 digits though to carryout the lookup so it becomes 003A
• Ensure you add 0’s and NOT O’s !!!!!
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Create the nslookup
• The last thing to do before you type the nslookup into the SGSN is ensure you are using the correct syntax.
• The SGSN checks a different db file in the DNS for RAC/LAC lookups so the syntax for the lookup needs to change
• Nslookup racxxxx.lacxxxx.mnc0014.mcc00EA.gprs.
• So our example becomes rac003A.lac003A.mnc0014.mnc00EA.gprs.
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From the above text we can see the DNS the SGSN polled (217.171.140.29 = BM-Gn1) And also the answer that was returned 217.171.141.116.
So now all we have to do is find out the SGSN with this address ??
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Loopback address
• Unfortunately from the previous slide there is no quick check to determine the SGSN with this IP address it’s a matter of looking.
• First you need to know where to look though and you need to realise that the address is the loopback address of the SMM card that hosts that RAC/LAC not the loopback address of the SGSN itself !
• Basically though 217.171 is common to them all and 140 is HH, 141 is BM and 142 is MR. The last bit you need to find yourself
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You need to login to the SGSN and go to Configuration > Line Cards > Choose either SMM card so either slot 1 or 10The Interfaces and you get the page above.
You’ll see in the loopback address’s the IP address we are looking for.