C
HAPTER
18
| General IP Routing
IP Routing and Switching
– 491 –
broadcast to get the destination MAC address from the destination node.
The IP packet can then be sent directly with the destination MAC address.
If the destination belongs to a different subnet on this switch, the packet
can be routed directly to the destination node. However, if the packet
belongs to a subnet not included on this switch, then the packet should be
sent to the next hop router (with the MAC address of the router itself used
as the destination MAC address, and the destination IP address of the
destination node). The router will then forward the packet to the
destination node through the correct path. The router can also use the ARP
protocol to find out the MAC address of the destination node of the next
router as necessary.
N
OTE
:
In order to perform IP switching, the switch should be recognized by
other network nodes as an IP router, either by setting it as the default
gateway or by redirection from another router via the ICMP process.
When the switch receives an IP packet addressed to its own MAC address,
the packet follows the Layer 3 routing process. The destination IP address
is checked against the Layer 3 address table. If the address is not already
there, the switch broadcasts an ARP packet to all the ports on the
destination VLAN to find out the destination MAC address. After the MAC
address is discovered, the packet is reformatted and sent out to the
destination. The reformat process includes decreasing the Time-To-Live
(TTL) field of the IP header, recalculating the IP header checksum, and
replacing the destination MAC address with either the MAC address of the
destination node or that of the next hop router.
When another packet destined to the same node arrives, the destination
MAC can be retrieved directly from the Layer 3 address table; the packet is
then reformatted and sent out the destination port. IP switching can be
done at wire-speed when the destination address entry is already in the
Layer 3 address table.
If the switch determines that a frame must be routed, the route is
calculated only during setup. Once the route has been determined, all
packets in the current flow are simply switched or forwarded across the
chosen path. This takes advantage of the high throughput and low latency
of switching by enabling the traffic to bypass the routing engine once the
path calculation has been performed.
R
OUTING
P
ATH
M
ANAGEMENT
Routing Path Management involves the determination and updating of all
the routing information required for packet forwarding, including:
u
Handling routing protocols
u
Updating the routing table
u
Updating the Layer 3 switching database
Содержание DG-GS4826S
Страница 2: ...DG GS4826S DG GS4850S E012011 R01 F1 2 2 0 ...
Страница 4: ......
Страница 6: ...ABOUT THIS GUIDE 6 ...
Страница 60: ...SECTION I Getting Started 60 ...
Страница 72: ...CHAPTER 1 Introduction System Defaults 72 ...
Страница 90: ...CHAPTER 2 Initial Switch Configuration Managing System Files 90 ...
Страница 92: ...SECTION II Web Configuration 92 u Unicast Routing on page 539 u Multicast Routing on page 595 ...
Страница 137: ...CHAPTER 4 Basic Management Tasks Resetting the System 137 Figure 23 Restarting the Switch Regularly ...
Страница 138: ...CHAPTER 4 Basic Management Tasks Resetting the System 138 ...
Страница 204: ...CHAPTER 6 VLAN Configuration Configuring MAC based VLANs 204 ...
Страница 212: ...CHAPTER 7 Address Table Settings Clearing the Dynamic Address Table 212 ...
Страница 238: ...CHAPTER 9 Rate Limit Configuration 238 Figure 106 Configuring Rate Limits ...
Страница 268: ...CHAPTER 12 Quality of Service Attaching a Policy Map to a Port 268 ...
Страница 368: ...CHAPTER 14 Security Measures DHCP Snooping 368 ...
Страница 422: ...CHAPTER 15 Basic Administration Protocols Remote Monitoring 422 ...
Страница 466: ...CHAPTER 16 Multicast Filtering Multicast VLAN Registration 466 Figure 273 Showing All MVR Groups Assigned to a Port ...
Страница 487: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 487 Figure 285 Showing Reported MTU Values ...
Страница 488: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 488 ...
Страница 538: ...CHAPTER 20 IP Services Forwarding UDP Service Requests 538 ...
Страница 594: ...CHAPTER 21 Unicast Routing Configuring the Open Shortest Path First Protocol Version 2 594 ...
Страница 624: ...CHAPTER 22 Multicast Routing Configuring PIMv6 for IPv6 624 ...
Страница 638: ...CHAPTER 23 Using the Command Line Interface CLI Command Groups 638 ...
Страница 712: ...CHAPTER 26 SNMP Commands 712 ...
Страница 720: ...CHAPTER 27 Remote Monitoring Commands 720 ...
Страница 776: ...CHAPTER 29 Authentication Commands Management IP Filter 776 ...
Страница 876: ...CHAPTER 34 Port Mirroring Commands Local Port Mirroring Commands 876 ...
Страница 898: ...CHAPTER 37 Address Table Commands 898 ...
Страница 998: ...CHAPTER 41 Quality of Service Commands 998 ...
Страница 1060: ...CHAPTER 42 Multicast Filtering Commands MLD Proxy Routing 1060 ...
Страница 1078: ...CHAPTER 43 LLDP Commands 1078 ...
Страница 1088: ...CHAPTER 44 Domain Name Service Commands 1088 ...
Страница 1164: ...CHAPTER 47 IP Interface Commands IPv6 to IPv4 Tunnels 1164 ...
Страница 1260: ...CHAPTER 48 IP Routing Commands Open Shortest Path First OSPFv3 1260 ...
Страница 1304: ...SECTION IV Appendices 1304 ...
Страница 1310: ...APPENDIX A Software Specifications Management Information Bases 1310 ...
Страница 1343: ...DG GS4826S DG GS4850S E012011 R02 F1 2 2 0 ...
Страница 1344: ......