Refer to the exhibit. A network administrator is troubleshooting BGP configuration and wants to display only routes with AS 300 being the first AS in the AS_Path value. Which regular expression should the administrator use in the command show bgp ipv4 unicast regex regex-pattern ?

In troubleshooting BGP, Regular expressions (regex) can be used to parse through the large number of available ASNs. Regular expressions are based on query modifiers used to select the appropriate content. The regex pattern ^300_ indicates to only include the lines that list the exact phrase of 300 as the first AS. Some regex query modifiers are as follows:
_ (underscore) – matches a space
^ (caret) – indicates the start of a string
$ (dollar sign) – indicates the end of a string
. (period) – matches a single character, including a space