D-Link DES-6500 Router Manual PDF (Setup & Configuration Guide)

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RIP Version 1 Message Format

There are two types of RIP messages: routing information messages and information requests.

The same format is used by both types.

The COMMAND field specifies an operation according the following table:

Command

Meaning

1

Request for partial or full routing information

2

Response containing network-distance pairs

from sender’s routing table

3

Turn on trace mode (obsolete)

4

Turn off trace mode (obsolete)

5

Reserved for Sun Microsystem’s internal use

9

Update Request

10

Update Response

11

Update Acknowledgement

RIP Command Codes

The field VERSION contains the protocol version number (1 in this case), and is used by the

receiver to verify which version of RIP the packet was sent.

RIP 1 Message

RIP is not limited to TCP/IP.

Its address format can support up to 14 octets (when using IP,

the remaining 10 octets must be zeros).

Other network protocol suites can be specified in the

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Family of Source Network field (IP has a value of 2).

This will determine how the address

field is interpreted.

RIP specifies that the IP address 0.0.0.0 denotes a default route.

The distances, measured in router hops are entered in the Distance to Source Network, and

Distance to Destination Network fields.

RIP 1 Route Interpretation

RIP was designed to be used with classed address schemes, and does not include an explicit

subnet mask.

An extension to version 1 does allow routers to exchange subnetted addresses,

but only if the subnet mask used by the network is the same as the subnet mask used by the

address.

This means the RIP version 1 cannot be used to propagate classless addresses.

Routers running RIP version 1 must send different update messages for each IP interface to

which it is connected.

Interfaces that use the same subnet mask as the router’s network can

contain subnetted routes, other interfaces cannot.

The router will then advertise only a single

route to the network.

RIP Version 2 Extensions

RIP version 2 includes an explicit subnet mask entry, so RIP version 2 can be used to

propagate variable length subnet addresses or CIDR classless addresses.

RIP version 2 also

adds an explicit next hop entry, which speeds convergence and helps prevent the formation of

routing loops.

RIP2 Message Format

The message format used with RIP2 is an extension of the RIP1 format:

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RIP version 2 also adds a 16-bit route tag that is retained and sent with router updates.

It can

be used to identify the origin of the route.

Because the version number in RIP2 occupies the same octet as in RIP1, both versions of the

protocols can be used on a given router simultaneously without interference.

Enabling RIP

RIP can be

Enabled

or

Disabled

, globally on the switch, using the

RIP Configuration

link

to open the RIP Global Setting window, as shown below.

Figure 4- 58. RIP Global Setting window

Select

Enable

or

Disable

, as appropriate.

Setting Up RIP

RIP settings are configured for each IP interface on the switch. Click the RIP Interface

Settings link in the RIP folder. The menu appears in table form listing settings for IP

interfaces currently on the switch. To configure RIP settings for an individual interface, click

on the hyperlinked name of the interface.

Figure 4- 59. RIP Interface Settings window

Click the name of the interface you want to setup for RIP to the following menu:

Figure 4- 60. RIP Interface Settings – Edit window

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Refer to the table below for a description of the available parameters for RIP interface

settings.

The following RIP settings can be applied to each IP interface:

Parameter

Description

Interface Name

The name of the IP interface on which RIP is to be setup. This interface

must be previously configured on the Switch.

TX Mode <

Disabled

>

Toggle among

Disabled

,

V1 Only

,

V1 Compatible

, and

V2 Only

. This entry

specifies which version of the RIP protocol will be used to transmit RIP

packets.

Disabled

prevents the transmission of RIP packets.

RX Mode <

Disabled

>

Toggle among

Disabled

,

V1 Only

,

V2 Only

, and

V1 and V2

. This entry

specifies which version of the RIP protocol will be used to interpret

received RIP packets.

Disabled

prevents the reception of RIP packets.

Password

A password to be used to authenticate communication between routers on

the network.

Authentication

Toggle between

Disabled

and

Enabled

to specify that routers on the

network should us the Password above to authenticate router table

exchanges.

State

Toggle between

Disable

and

Enable

to disable or enable this RIP interface

on the switch.

Configuring OSPF

OSPF Authentication

OSPF packets can be authenticated as coming from trusted routers by the use of predefined

passwords.

The default for routers is to use not authentication.

There are two other authentication methods

−

simple password authentication (key) and

Message Digest authentication (MD-5).

Message Digest Authentication (MD-5)

MD-5 authentication is a cryptographic method. A key and a key-ID are configured on each

router.

The router then uses an algorithm to generate a mathematical “message digest” that is

derived from the OSPF packet, the key and the key-ID.

This message digest (a number) is

then appended to the packet.

The key is not exchanged over the wire and a non-decreasing

sequence number is included to prevent replay attacks.

Simple Password Authentication

A password (or key) can be configured on a per-area basis.

Routers in the same area that

participate in the routing domain must be configured with the same key.

This method is

possibly vulnerable to passive attacks where a link analyzer is used to obtain the password.

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The Backbone and Area 0

OSPF limits the number of link-state updates required between routers by defining areas

within which a given router operates.

When more than one area is configured, one area is

designated as area 0

−

also called the backbone.

The backbone is at the center of all other areas

−

all areas of the network have a physical (or

virtual) connection to the backbone through a router.

OSPF allows routing information to be

distributed by forwarding it into area 0, from which the information can be forwarded to all

other areas (and all other routers) on the network.

In situations where an area is required, but is not possible to provide a physical connection to

the backbone, a virtual link can be configured.

Virtual Links

Virtual links accomplish two purposes:

Linking an area that does not have a physical connection to the backbone.

Patching the backbone in case there is a discontinuity in area 0.

Areas Not Physically Connected to Area 0

All areas of an OSPF network should have a physical connection to the backbone, but is some

cases it is not possible to physically connect a remote area to the backbone. In these cases, a

virtual link is configured to connect the remote area to the backbone. A virtual path is a

logical path between two border routers that have a common area, with one border router

connected to the backbone.

Partitioning the Backbone

OSPF also allows virtual links to be configured to connect the parts of the backbone that are

discontinuous.

This is the equivalent to linking different area 0s together using a logical path

between each area 0.

Virtual links can also be added for redundancy to protect against a

router failure.

A virtual link is configured between two border routers that both have a

connection to their respective area 0s.

Neighbors

Routers that are connected to the same area or segment become neighbors in that area.

Neighbors are elected via the Hello protocol.

IP multicast is used to send out Hello packets to

other routers on the segment.

Routers become neighbors when they see themselves listed in a

Hello packet sent by another router on the same segment.

In this way, two-way

communication is guaranteed to be possible between any two neighbor routers.

Any two routers must meet the following conditions before the become neighbors:

Area ID

−

two routers having a common segment

−

their interfaces have to belong to the

same area on that segment.

Of course, the interfaces should belong to the same subnet

and have the same subnet mask.

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