Hello,
1): What is difference between line console and line default in IOS-XR?
The IOS equivalent of 'line console' is 'line con 0', so basically it is for configuring the console port line
The IOS equivalent of 'line default' is 'line vty 0', so with 'line default' you configure the virtual terminal (telnet) line (just the first one, 0)
2): What is line line template <name> in IOS-XR?
The 'line template' lets you configure a user-defined, customized line
3): What is vty pool in IOS-XR?
The IOS equivalent would be 'line vty 0/x', which allows you to configure several VTY lines at the same time, all with the same characteristics
4): What is line preferred none under line console configuration?
I don't see the 'preferred' kerword in XR under the line console. Do you mean 'transport preferred' ?
Check the links below as well:
https://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r4-2/system_management/configuration/guide/b_sysman_cg42crs/b_sysman_cg42crs_chapter_01011.html
https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r3-9/system_management/command/reference/yr39xr12k_chapter16.html#wp262121984
