ZyXEL Communications Cable Modem, User Manual

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Chapter 1 VLC Overview
VLC1324G User’s Guide
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DHCP Relay
DHCP (Dynamic Host Configuration Protocol RFC 2131 and RFC 2132) allows individual
computers to obtain TCP/IP configuration at start-up from a server. You can configure the
system as a DHCP relay agent to have another DHCP server provide TCP/IP configuration for
the clients. In addition, you can set the system to forward client DHCP requests to specific
DHCP servers based on the VLAN ID. You can also specify up to two DHCP servers for each
VLAN to provide failover protection.
Rate Limiting
Rate limiting on the subscriber ports allows service providers to offer tiered service in
increments of 64 Kbps. This service differentiation is not only to fulfill the needs of different
customers, but also to provide a network infrastructure that combines guaranteed performance
and flexibility in service provisioning.
DHCP Relay Option 82
The system supports DHCP relay agent82 (RFC 3046) that adds additional information to
client DHCP requests that the MSC relays to a DHCP server. It also supports adding the sub-
option 2 (Remote ID) with additional information.
DHCP Snooping
DHCP snooping allows the system to identify packets with DHCP server assigned IP
address(es) and block access of devices using unknown IP addresses on a subscriber port. You
can also manually add static IP addresses to the DHCP snooping table.
Anti-IP Address Spoofing
With DHCP snooping, a line card records which IP addresses are assigned on each port. The
line card drops packets from a device using a different IP address.
Anti-MAC Address Spoofing
The VLC checks to make sure the MAC addresses of the devices connected to the DSL ports
are not the same as MAC addresses of devices connected to the Ethernet network. This
protects the network from disruptions of service caused by subscriber devices spoofing the
MAC address of ISP servers.
Transparent LAN Service (TLS)
Use TLS (also known as VLAN stacking) to add an outer VLAN tag to the inner IEEE 802.1Q
tagged frames that enter the network. This allows a service provider to provide different
services based on specific VLANs, for many different customers.
1.4 Front Panel of VLC
The figure below shows the front panel of the VLC.