This effort involve two main steps on router as well as external resource, like: XR image is availabe on external tftp server and should be accessibe by this router.
Mainly we need perform router pre-configuration in boothelper mode, and load image from tftp server and bootup from ROMMON mode.
Step 1
bring RP to boothelper mode, and perform router pre-configuration.
note: you can not bring only standby RP to boothelper while active RP is XR RUN. you have to bring dowm whole router to ROMMON first.
If router has no image, it will be in rommon mode first. Then just enter "boot" command to take RP to boothelper.
rommon 1 > boot
pre-configuration in boothelper.
Router(boot)>enable
Router(boot)#config t
Router(boot)#(config-interf)interface ether 0
Router(boot)#(config-interf)ip add x.x.x.x x.x.x.x
Router(boot)#(config-interf)no shu
Router(boot)#(config)ip default gateway x.x.x.x
Router(boot)#(config)write memory
Router(boot)#(config)config Regis 0x0
Router(boot)#ping 223.255.254.254 (e.g. 223.255.254.254 is location of XR image on tftp server, confirm it is accessable)
Router(boot)#reload (bring RP into ROMMON mode from boothelper status)
step 2
In ROMMON, we need set proper ROMMON variables then load image from tftp server and bootup.
rommon 1 > set
PS1=rommon ! >
CONFIG_FILE=
BOOTLDR=
CONFGEN=4570
CHASSIS_SN=TBTB60TB111
RET_2_RUTC=1204565037
NT_K=0:0:0:0
RET_2_RTS=20:23:24 UTC Wed Mar 19 2008
RET_2_RCALTS=1205958205
IOX_CONFIG_MEDIUM=
IOX_CONFIG_FILE=
IOX_ADMIN_CONFIG_FILE=
BOOT=disk0:c12k-os-mbi-3.7.0.14I/mbiprp-rp.vm,1;
BSI=0
ReloadReason=1
?=0
TURBOBOOT=on,disk0
rommon 4>unset BOOT <<<<<<<<<<<<<<<<<<
rommon 5>sync
rommon 1 > set
PS1=rommon ! >
CONFIG_FILE=
BOOTLDR=
CONFGEN=4570
CHASSIS_SN=TBTB60TB111
RET_2_RUTC=1204565037
NT_K=0:0:0:0
RET_2_RTS=20:23:24 UTC Wed Mar 19 2008
RET_2_RCALTS=1205958205
IOX_CONFIG_MEDIUM=
IOX_CONFIG_FILE=
IOX_ADMIN_CONFIG_FILE=
BSI=0
ReloadReason=1
?=0
TURBOBOOT=on,disk0
rommon 1 > boot tftp://223.255.254.254/harlin/qnxmerge/c12k-mini.vm
Self decompressing the image : BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB [OK]
Loading harlin/qnxmerge/c12k-mini.vm from 223.255.254.254 (via Ethernet0): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!