Configuring Persistent Bindings in the DHCP or DHCPv6 (non-ELS)
This task uses Junos OS without support for the Enhanced Layer 2 Software (ELS) configuration style. If your switch runs software that supports ELS, seeConfiguring Persistent Bindings in the DHCP or DHCPv6 (ELS) instead. For ELS details, see Using the Enhanced Layer 2 Software CLI.
By default, IP-MAC bindings in the DHCP snooping database do not persist through switch reboots. You can configure the IP-MAC bindings in the DHCP snooping database to persist through switch reboots by configuring a storage location for the DHCP snooping database file. When specifying the location for the DHCP snooping database, you must also specify how frequently the switch writes the database entries into the DHCP snooping database file.
The DHCP snooping database of IP-MAC bindings is created when you enable DHCP snooping. DHCP snooping is not enabled by default. You can configure DHCP snooping on a specific VLAN or on all VLANs. See Enabling DHCP Snooping (non-ELS).
To configure a local storage location for the DHCP snooping database file:
For DHCPv4 snooping:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcp-snooping-file location local-pathname write-interval seconds
For example:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcp-snooping-file location /var/tmp/test.log write-interval 60
For DHCPv6 snooping:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcpv6-snooping-file location local-pathname write-interval seconds
For example:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcpv6-snooping-file location /var/tmp/test.log write-interval 60
To configure a remote storage location for IP-MAC bindings, use tftp://ip-address or ftp://hostname/path as the remote URL or the local pathname for the storage location of the DHCP or DHCPv6 snooping database file:
For DHCPv4 snooping:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcp-snooping-file location remote_url write-interval seconds
For example:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcp-snooping-file location ftp://test:Test123@14.1.2.1 write-interval 60
For DHCPv6 snooping:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcpv6-snooping-file location remote_url write-interval seconds
For example:
[edit ethernet-switching-options] user@switch# set secure-access-port dhcpv6-snooping-file location ftp://test:Test123@14.1.2.1 write-interval 60
If you save the DHCP or DHCPv6 snooping file to a remote server using TFTP, then the CLI returns a message that the save process is initiated. The CLI remains accessible during the save process; however, if you attempt to save a file while the previous save is still pending, the CLI returns an error message.
Specify any requisite user credentials for the FTP server before you specify the IP address or hostname. In this example, test is the username and Test123 is the password for FTP server 14.1.2.1.
When you are storing the DHCP snooping database at a remote location, you might also
want to specify a timeout value for remote read and write operations. See timeout. This configuration is
optional.
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