In 3660 router, after configuring the router while saving to NVRAM by wr mem or copy run start I am getting the message failed to save.See the below sh ver shows -2K bytes of NVRAM.
What went wrong and If the nvram faulty is it field replaceable or it is builtin memory so that we have to buy the whole router unit.
------------------ show version ------------------
Cisco IOS Software, 3600 Software (C3660-I-M), Version 12.4(2)T3, RELEASE SOFTWARE (fc4)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Jan-06 22:10 by ccai
ROM: System Bootstrap, Version 12.0(6r)T, RELEASE SOFTWARE (fc1)
Router uptime is 6 hours, 16 minutes
System returned to ROM by unknown reload cause - suspect boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19
System image file is "flash:c3660-i-mz.124-2.T3.bin"
Cisco 3660 (R527x) processor (revision 1.0) with 120832K/10240K bytes of memory.
Processor board ID JAB0436C05W
R527x CPU at 225MHz, Implementation 40, Rev 10.0, 2048KB L2 Cache
3660 Chassis type: ENTERPRISE
1 FastEthernet interface
4 Serial interfaces
1 Channelized (E1 or T1)/PRI port
DRAM configuration is 64 bits wide with parity disabled.
-2K bytes of NVRAM.
32768K bytes of processor board System flash (Read/Write)
Configuration register is 0x101 (will be 0x0 at next reload)