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With this feature, the DHCP relay agent uses the following information to periodically send a
DHCP-REQUEST message to the DHCP server:
•
The IP address of a relay entry.
•
The MAC address of the DHCP relay interface.
The relay agent maintains the relay entries depending on what it receives from the DHCP server:
•
If the server returns a DHCP-ACK message or does not return any message within an interval,
the DHCP relay agent removes the relay entry. In addition, upon receiving the DHCP-ACK
message, the relay agent sends a DHCP-RELEASE message to release the IP address.
•
If the server returns a DHCP-NAK message, the relay agent keeps the relay entry.
HTTP/HTTPS
The device provides a built-in Web server. After you enable the Web server on the device, users can
log in to the Web interface to manage and monitor the device.
The device's built-in Web server supports both Hypertext Transfer Protocol (HTTP) (version 1) and
Hypertext Transfer Protocol Secure (HTTPS). HTTPS is more secure than HTTP because of the
following items:
•
HTTPS uses SSL to ensure the integrity and security of data exchanged between the client and
the server.
•
HTTPS allows you to define a certificate attribute-based access control policy to allow only legal
clients to access the Web interface.
You can also specify a basic ACL for HTTP or HTTPS to prevent unauthorized Web access.
•
If you does not specify an ACL for HTTP or HTTPS, or the specified ACL does not exist or does
not have rules, the device permits all HTTP or HTTPS logins.
•
If the specifies ACL has rules, only users permitted by the ACL can log in to the Web interface
through HTTP or HTTPS.
SSH
SSH is not available in Release 3111P02.
Secure Shell (SSH) is a network security protocol. Using encryption and authentication, SSH can
implement secure remote access and file transfer over an insecure network.
SSH uses the typical client-server model to establish a channel for secure data transfer based on
TCP.
SSH includes two versions: SSH1.x and SSH2.0 (hereinafter referred to as SSH1 and SSH2), which
are not compatible. SSH2 is better than SSH1 in performance and security.
The device can act as an SSH server to provide the following SSH applications to SSH clients:
•
Secure
Telnet
—Stelnet provides secure and reliable network terminal access services.
Through Stelnet, a user can securely log in to a remote server. Stelnet can protect devices
against attacks, such as IP spoofing and plain text password interception. The device can act
as an Stelnet server or an Stelnet client.
•
Secure File Transfer Protocol
—Based on SSH2, SFTP uses SSH connections to provide
secure file transfer.
•
Secure
Copy
—Based on SSH2, SCP offers a secure method to copy files.
When acting as an Stelnet, SFTP, or SCP server, the device supports both SSH2 and SSH1 in
non-FIPS mode and only SSH2 in FIPS mode.
