Hi,
I guess this question is more appropriate to Unix sa's not to sybase dba's.
If you have a n/w device, then you should ask your unix sa to mount it under some mount pioint and let you know the mount point.
Now you can use this mount point as normal file system and take dump of your databases using sybase command
dump database <db_name> to '<path of the mount poin>/<backup_filename>'