Moxa EDS-82810G [85/113] Using layer 3 settings

EDS-828 Series Featured Functions

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Using Layer 3 Settings

The EDS-828 is a Layer-3 switch that performs data switching on the Network Layer (Layer 3) of the ISO’s OSI

layer model. Unlike Layer-2 switching, which uses the MAC address for exchanging data, a Layer-3 switch uses

the IP address to represent the destination of a data packet.

Layer

-2 switching

Layer

-3 switching

The Layer-3 Switching Concept

IP (Internet Protocol) is a protocol defined on layer 3 of the 7-layer OSI model. The IP address is used to

address data packets on the Network Layer, and is not tied to the hardware of a device or PC. The IP address

can be assigned by the system operator or network administrator.

Since Layer 2 switches use the MAC address to determine the destination of transmitted data packets, and

Layer 3 switches use IP address, some mechanism is needed to associate MAC addresses with IP addresses.

This is done by ARP (Address Resolution Protocol), which creates a table that matches MAC addresses to IP

addresses.

When a PC sends out an ARP request, which is just a broadcast packet requiring the IP address owner to send

back his MAC address, two situations could occur:

• If your PC and the IP address owner are on the same subnet, the IP address owner will use a unicast packet,

which contains his MAC address, to reply to your PC. There after your PC will use this MAC address to

transmit to the IP address owner directly.

• If your PC and the IP address owner are not on the same subnet, your PC will not receive a reply, so it will

ask for the MAC address of the Layer-3 switch (gateway/ router). To transmit data packets to the IP address

owner, your PC packs the data packet with the IP address, and sends the packet to the Layer-3 switch

(gateway/router) using its MAC address. The Layer-3 switch (gateway/router) receives the data packet,

re-packs it, and then forwards it to the next hop according to the routing rules.

Static Routing and Dynamic Routing

The EDS-828 supports two routing methods: static routing and dynamic routing. Dynamic routing makes use

of RIP V1/V1c/V2, and OSPF. You can either choose one routing method, or combine the two methods to

establish your routing table.

A routing entry includes the following items: the destination address, the next hop address (which is the next

router along the path to the destination address), and a metric that represents the cost we have to pay to

access a different network.

Static Route

You can define the routes yourself by specifying what is the next hop (or router) that the EDS-828 forwards

data for a specific subnet. The settings of the Static Route will be added to the routing table and stored in the

EDS-828.

RIP (Routing Information Protocol)

RIP is a distance vector-based routing protocol that can be used to automatically build up a routing table in the

EDS-828.