5
Layer 2 switching
• VLAN: supports up to 4,096 port or IEEE
802.1Q-based VLANs; also supports MAC-based
VLANs, protocol-based VLANs, and IP-subnet-based
VLANs for added flexibility
• Port isolation: increases security by isolating
ports within a VLAN while still allowing them to
communicate with other VLANs
• Bridge Protocol Data Unit (BPDU) tunneling:
transmits Spanning Tree Protocol BPDUs
transparently, allowing correct tree calculations
across service providers, WANs, or MANs
• GARP VLAN Registration Protocol: allows
automatic learning and dynamic assignment of
VLANs
• Port mirroring: duplicates port traffic (ingress
and egress) to a local or remote monitoring port;
supports four mirroring groups, with an unlimited
number of ports per group
• Spanning Tree Protocol: fully supports standard
IEEE 802.1D Spanning Tree Protocol, IEEE 802.1w
Rapid Spanning Tree Protocol for faster
convergence, and IEEE 802.1s Multiple Spanning
Tree Protocol
• Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery
(MLD) protocol snooping: effectively control
and manage the flooding of multicast packets in a
Layer 2 network
• Device Link Detection Protocol (DLDP):
monitors link connectivity and shuts down ports at
both ends if uni-directional traffic is detected,
preventing loops in STP-based networks
• IEEE 802.1ad QinQ and Selective QinQ:
increase the scalability of an Ethernet network by
providing a hierarchical structure; connect multiple
LANs on a high-speed campus or metro network
• Super VLAN: RFC 3069 standard, also called
VLAN aggregation, is used to save IP address space
• Per-VLAN Spanning Tree Plus (PVST+):
allows each virtual LAN (VLAN) to build a separate
spanning tree to improve link bandwidth usage in
network environments where multiple VLANs exist
Layer 3 services
• Address Resolution Protocol (ARP):
determines the MAC address of another IP host in
the same subnet; supports static ARPs; gratuitous
ARP allows detection of duplicate IP addresses;
proxy ARP allows normal ARP operation between
subnets or when subnets are separated by a Layer 2
network
• User Datagram Protocol (UDP) helper:
redirects UDP broadcasts to specific IP subnets to
prevent server spoofing
• Dynamic Host Configuration Protocol
(DHCP): simplifies the management of large IP
networks and supports client and server; DHCP
Relay enables DHCP operation across subnets
• Domain Name System (DNS): is a distributed
database that provides translation between a
domain name and an IP address, which simplifies
network design; supports client and server
Layer 3 routing
• Static IPv4 routing: provides simple, manually
configured IPv4 routing
• Routing Information Protocol: uses a distance
vector algorithm with UDP packets for route
determination; supports RIPv1 and RIPv2 routing;
includes loop protection
• OSPF: Interior Gateway Protocol (IGP) uses
link-state protocol for faster convergence; supports
ECMP, NSSA, and MD5 authentication for
increased security and graceful restart for faster
failure recovery
• Intermediate system to intermediate
system (IS-IS): Interior Gateway Protocol (IGP)
uses path vector protocol, which is defined by the
ISO organization for IS-IS routing and extended by
IETF RFC 1195 to operate in both TCP/IP and the
OSI reference model (Integrated IS-IS)
• Border Gateway Protocol 4 (BGP-4): Exterior
Gateway Protocol (EGP) with path vector protocol
uses TCP for enhanced reliability for the route
discovery process, reduces bandwidth consumption
by advertising only incremental updates, and
supports extensive policies for increased flexibility,
as well as scales to very large networks
• Policy-based routing: makes routing decisions
based on policies set by the network administrator
• IP performance optimization: is a set of tools
to improve the performance of IPv4 networks;
includes directed broadcasts, customization of TCP
parameters, support of ICNP error packets, and
extensive display capabilities
