
C
HAPTER
18
| General IP Routing
IP Routing and Switching
– 743 –
If the destination node is on the same subnetwork as the source network,
then the packet can be transmitted directly without the help of a router.
However, if the MAC address is not yet known to the switch, an Address
Resolution Protocol (ARP) packet with the destination IP address is
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:
◆
Handling routing protocols
◆
Updating the routing table
◆
Updating the Layer 3 switching database
Содержание ECS4660-28F
Страница 1: ...Management Guide www edge core com ECS4660 28F Layer 3 Gigabit Ethernet Switch...
Страница 2: ......
Страница 4: ......
Страница 12: ...ABOUT THIS GUIDE 12...
Страница 64: ...CONTENTS 64...
Страница 90: ...TABLES 90...
Страница 92: ...SECTION I Getting Started 92...
Страница 122: ...SECTION II Web Configuration 122 Multicast Routing on page 825...
Страница 148: ...CHAPTER 3 Using the Web Interface Navigating the Web Browser Interface 148...
Страница 224: ...CHAPTER 5 Interface Configuration VLAN Trunking 224 Figure 68 Configuring VLAN Trunking...
Страница 262: ...CHAPTER 6 VLAN Configuration Configuring VLAN Translation 262...
Страница 304: ...CHAPTER 9 Congestion Control Automatic Traffic Control 304...
Страница 340: ...CHAPTER 11 Quality of Service Attaching a Policy Map to a Port 340...
Страница 452: ...CHAPTER 13 Security Measures DHCP Snooping 452...
Страница 740: ...CHAPTER 17 IP Services Configuring the PPPoE Intermediate Agent 740...
Страница 866: ...CHAPTER 21 Multicast Routing Configuring PIMv6 for IPv6 866...
Страница 882: ...CHAPTER 22 Using the Command Line Interface CLI Command Groups 882...
Страница 1024: ...CHAPTER 26 Remote Monitoring Commands 1024...
Страница 1030: ...CHAPTER 27 Flow Sampling Commands 1030...
Страница 1088: ...CHAPTER 28 Authentication Commands PPPoE Intermediate Agent 1088...
Страница 1162: ...CHAPTER 29 General Security Measures Configuring Port based Traffic Segmentation 1162...
Страница 1186: ...CHAPTER 30 Access Control Lists ACL Information 1186...
Страница 1214: ...CHAPTER 31 Interface Commands Transceiver Threshold Configuration 1214...
Страница 1238: ...CHAPTER 33 Port Mirroring Commands RSPAN Mirroring Commands 1238...
Страница 1258: ...CHAPTER 34 Congestion Control Commands Automatic Traffic Control Commands 1258...
Страница 1270: ...CHAPTER 36 UniDirectional Link Detection Commands 1270...
Страница 1276: ...CHAPTER 37 Address Table Commands 1276...
Страница 1336: ...CHAPTER 39 ERPS Commands 1336...
Страница 1386: ...CHAPTER 40 VLAN Commands Configuring Voice VLANs 1386...
Страница 1406: ...CHAPTER 41 Class of Service Commands Priority Commands Layer 3 and 4 1406...
Страница 1424: ...CHAPTER 42 Quality of Service Commands 1424...
Страница 1536: ...CHAPTER 43 Multicast Filtering Commands MLD Proxy Routing 1536...
Страница 1602: ...CHAPTER 45 CFM Commands Delay Measure Operations 1602...
Страница 1624: ...CHAPTER 47 Domain Name Service Commands 1624...
Страница 1646: ...CHAPTER 48 DHCP Commands DHCP Server 1646...
Страница 1974: ...SECTION IV Appendices 1974...
Страница 1980: ...APPENDIX A Software Specifications Management Information Bases 1980...
Страница 2020: ...ECS4660 28F E102013 ST R03 149100000140A...