[windbg]pdb of ntdll version 6.1.7601.19045 is missing on the symbol server

Loaded symbol image file: ntdll.dll
Image path: C:\Windows\SysWOW64\ntdll.dll
Image name: ntdll.dll
Timestamp: Tue Oct 20 08:44:18 2015 (56258E62)
CheckSum: 00142AA7
ImageSize: 00180000
File version: 6.1.7601.19045
Product version: 6.1.7601.19045
File flags: 0 (Mask 3F)
File OS: 40004 NT Win32
File type: 2.0 Dll
File date: 00000000.00000000
Translations: 0409.04b0
CompanyName: Microsoft Corporation
ProductName: Microsoft? Windows? Operating System
InternalName: ntdll.dll
OriginalFilename: ntdll.dll
ProductVersion: 6.1.7601.19045
FileVersion: 6.1.7601.19045 (win7sp1_gdr.151019-1254)
FileDescription: NT Layer DLL
LegalCopyright: ? Microsoft Corporation. All rights reserved.