Netgear M5300-28G3 (GSM7328Sv2h2) - ProSAFE 24+4 Gigabit Ethernet L3 Managed Stackable Switch 管理者ガイド
Port Routing
103
Managed Switches
Port Routing Concepts
The first networks were small enough for the end stations to communicate directly. As
networks grew, Layer 2 bridging was used to segregate traffic, a technology that worked well
for unicast traffic, but had problems coping with large quantities of multicast packets. The
next major development was routing, where packets were examined and redirected at
Layer
networks grew, Layer 2 bridging was used to segregate traffic, a technology that worked well
for unicast traffic, but had problems coping with large quantities of multicast packets. The
next major development was routing, where packets were examined and redirected at
Layer
3. End stations needed to know how to reach their nearest router, and the routers had
to interpret the network topology so that they could forward traffic. Although bridges tended to
be faster than routers, using routers allowed the network to be partitioned into logical
subnetworks, which restricted multicast traffic and also facilitated the development of security
mechanisms.
be faster than routers, using routers allowed the network to be partitioned into logical
subnetworks, which restricted multicast traffic and also facilitated the development of security
mechanisms.
An end station specifies the destination station’s Layer 3 address in the packet’s IP header,
but sends the packet to the MAC address of a router. When the Layer 3 router receives the
packet, it will minimally:
packet, it will minimally:
•
Look up the Layer 3 address in its address table to determine the outbound port.
•
Update the Layer 3 header.
•
Re-create the Layer 2 header.
The router’s IP address is often statically configured in the end station, although the
managed switch supports protocols such as DHCP that allow the address to be assigned
dynamically. Likewise, you can assign some of the entries in the routing tables used by the
router statically, but protocols such as RIP and OSPF allow the tables to be created and
updated dynamically as the network configuration changes.
managed switch supports protocols such as DHCP that allow the address to be assigned
dynamically. Likewise, you can assign some of the entries in the routing tables used by the
router statically, but protocols such as RIP and OSPF allow the tables to be created and
updated dynamically as the network configuration changes.
Port Routing Configuration
The managed switch always supports Layer 2 bridging, but Layer 3 routing must be explicitly
enabled, first for the managed switch as a whole, and then for each port that is to be part of
the routed network.
enabled, first for the managed switch as a whole, and then for each port that is to be part of
the routed network.
The configuration commands used in the example in this section enable IP routing on ports
1/0/2,1/0/3, and 1/0/5. The router ID will be set to the managed switch’s management IP
address, or to that of any active router interface if the management address is not configured.
1/0/2,1/0/3, and 1/0/5. The router ID will be set to the managed switch’s management IP
address, or to that of any active router interface if the management address is not configured.
After the routing configuration commands have been issued, the following functions will be
active:
•
IP forwarding, responsible for forwarding received IP packets.
•
ARP mapping, responsible for maintaining the ARP Table used to correlate IP and MAC
addresses. The table contains both static entries and entries dynamically updated based
on information in received ARP frames.
on information in received ARP frames.
•
Routing Table Object, responsible for maintaining the common routing table used by all
registered routing protocols.
registered routing protocols.