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Configuring RIP Routing 2

This chapter describes the Routing Information Protocol (RIP) operation on PortMaster products and provides sample network configurations that show how to configure each PortMaster product in the network.

This chapter discusses the following topics:

"Understanding RIP" on page 2-1
"RIP Configuration Examples" on page 2-2
Use this chapter in conjunction with the PortMaster Command Line Administrator's Guide. Refer to the glossary and Chapter 1, "Routing Overview," for definitions of terms and for an explanation of how PortMaster products implement RIP.

Understanding RIP

RIP is an interior routing protocol that uses a distance-vector algorithm to optimize routing. The distance-vector algorithm used by RIP for making routing decisions is based on the number of hops to a destination. The route with the least number of hops is considered to have the lowest cost. The number of hops is referred to as the route metric. A route with a metric greater than 15 is considered to be unreachable.

Although the more accurate link state technology of the Open Shortest Path First routing protocol (OSPF) is the most common interior routing protocol, RIP is still widely used on routers in TCP/IP and in Novell IPX networks as the primary method for the exchange of routing information.

When using RIP, routing updates can be turned on or off for individual interfaces on the PortMaster, and each interface can be configured as follows:

Broadcast routing updates
Listen for routing updates
Broadcast and listen for routing updates
Neither broadcast nor listen for routing updates
When a PortMaster interface is configured to broadcast, it sends RIP information onto the network every 30 seconds. When a PortMaster interface is configured to listen, it receives RIP broadcasts from other routers on the network. Routing table entries are aged as follows for RIP:
Updates are expected every 30 seconds.
After 120 seconds if information for another route to a given destination is observed, the new route is used for the destination.
After 180 seconds without an update, a route is considered unreachable, and is made obsolete by having its metric set to 16.
The routing timer is suspended if an on-demand interface is suspended.
Routes are valid for active interfaces only.
If an interface fails, all routes that go through that interface are examined. If the specified gateway is available on another interface, the route is moved to the active interface. Otherwise the routing table entry is marked as obsolete-also referred to as poisoned.
When routing is enabled, a PortMaster broadcasts any default route and static route information as part of a normal RIP message.

RIP Configuration Examples

The examples in this section illustrate typical scenarios using RIP. Configurations are simplified to focus on the critical elements in each scenario. This section includes the following examples:

Figure 2-1 illustrates an appropriate implementation of subnetting. The example uses two class C addresses, one (192.168.100.0) for the local Ethernet segment and one (192.168.200.0) for dial-in users.

Routing with Subnets On the local Ethernet segment, an IRX at address 192.168.100.1/24 (netmask 255.255.255.0) is configured as the gateway router serving four PM-2ER-30s: Router 1 at address 192.168.100.2, Router 2 at 100.3, Router 3 at 100.4, and Router 4 at 100.5.

The second class C address, 192.168.200.0/27 (netmask 255.255.255.224) is divided into four subnets of 30 addresses each. Allowing for the use of the .0 subnet, this entire network is used for all the dial-in assigned pools. So the 192.168.200.0 is on 192.168.100.2, the 200.32 is on 100.3, the 200.64 is on 100.4, and the 200.96 is on 100.5. This is a convenient configuration because, with 30 dial-in ports on each PM-2ER-30, no addresses are wasted.

All the ports on the PM-2Es are configured for network dial-in, and routing is on by default-except during user configuration, when routing is set to off to ensure that it is disabled for dial-in clients.

Note ¯ On Ethernet interfaces, routing is off by default in ComOS 3.5 and earlier.

Using Proxy ARP

Proxy Address Resolution Protocol (ARP) is ARP for an IP address that is not local on the LAN. Figure 2-2 shows an example in which the PortMaster 3 Integrated Access Server acts as the proxy for dial-in users. The IP address of dial-in users must be in the same range as the Ethernet segment.

Figure 2-2 Proxy ARP

Configuration on the PortMaster 3

In addition to the regular configuration, enter the following commands to enable the PortMaster 3 to use proxy ARP for dial-in users:

1. Set the base address of the assigned address pool:
Command> set assigned_address 198.168.10.65
First Assigned address changed from 0.0.0.0 to 192.168.10.65
Set the size of the assigned pool of IP addresses:
Command> set pool 48
Assigned address pool size changed from 0 to 48
Save the configuration:
Command> save all

Configuring a Simple Dial-In Connection

Figure 2-3 shows a simple network structure in which two locations are connected via a serial interface through a dial-in connection. Router 1, which has a connection to the Internet, is the only router connected to Ethernet 1. Router 2 is the only router connected to Ethernet 2. All data traffic between hosts on Ethernet 2 and the Internet must therefore use Router 1 as a gateway.

Figure 2-3 Simple Dial-In Router Connection To make this connection possible, Router 2 must be configured so that hosts on Ethernet 2 can access the Internet via a dial-in PPP connection from Router 2 to Router 1, and Router 1 must be configured to accept a dial-in modem connection from Router 2.

Router 2 must broadcast RIP packets over the dial-in connection that contains route information about the Ethernet 2 network. Router 1 must listen for RIP packets over the dial-in connection to acquire the route information broadcast by Router 2.

Configuration on Router 1

In this example, a network user profile is configured for dial-in calls from Router 2. To keep the example focused, configuration of the WAN interface to the Internet is not considered. Router 1 is assumed to be a PortMaster IRX.

For more information, see the instructions for configuring dial-in connections in the Configuration Guide for PortMaster Products.

The complete configuration for Router 1 appears in the following box:

Command> set ether0 address 172.16.2.1
Command> add netuser prouter2 password ghrimpdezxt1
Command> set user prouter2 protocol ppp
Command> set user prouter2 destination 192.168.1.1
Command> set user prouter2 routing listen
Command> save all
Command> reboot

The following procedure shows the separate tasks involved in the configuration of Router 1:

Set the Ethernet interface address:
Command> set ether0 address 172.16.2.1
Local (ether0) changed from 0.0.0.0 to 172.16.2.1
Add a network user and password:
Command> add netuser prouter2 password ghrimpdezxt1
User successfully added
Set the network protocol to be used:
Command> set user prouter2 protocol ppp
Username: prouter2 Type: Dial-in Network User
Address: Negotiated Netmask: 255.255.255.0
Protocol: PPP Options: Quiet, Compression
MTU: 1500 Async Map: 00000000
Set the IP address of the remote router:
Command> set user prouter2 destination 192.168.1.1
Username: prouter2 Type: Dial-in Network User
Address: 192.168.1.1 Netmask: 255.255.255.0
Protocol: PPP Options: Quiet, Compression
MTU: 1500 Async Map: 00000000
Configure the router to receive RIP updates:
Command> set user prouter2 routing listen
Username: prouter2 Type: Dial-in Network User
Address: 192.168.1.1 Netmask: 255.255.255.0
Protocol: PPP Options: Quiet, Listen, Compression
MTU: 1500 Async Map: 00000000

Save the configuration and reboot:

Command> save all
Command> reboot

The show routes command issued on Router 1 now gives the following (partial) response:

Command> show routes

Destination
-----------
Gateway
-------
Flag
----
Met
---
Interface
---------

0.0.0.0
10.10.10.1
NS
1
ptp1

172.16.2.0
172.16.2.1
NL
1
ether0

192.168.1.1
192.168.1.1
HL
1
ptp2

192.168.1.0
192.168.1.1
ND
1
ptp2

The routes that Router 1 learned by listening to the RIP packets broadcast from Router 2 are shown in this router table.

Configuration on Router 2

This example assumes Router 2 to be a PortMaster 2E-30. The location table commands are used to set up the dial-out profile. Port S1 is used for the dial-out modem. To keep the examples focused on the routing configuration, global and host or user configurations are not shown.

For more information, see the instructions for configuring dial-out connections in the Configuration Guide for PortMaster Products.

The complete configuration for Router 2 appears in the following box:

The following procedure shows the separate tasks involved in the configuration of Router 2:

Set the Ethernet address on the interface connecting Router 2 to Router 1:
Command> set ether0 192.168.1.1
Local (ether0) changed from to 192.168.1.1
Set the gateway for this router:
Command set gateway 172.16.2.1
Gateway changed from 0.0.0.0 to 172.16.2.1
Add the location of Router 1 to the location table:
Command> add location loc_a
Location loc_a successfully added
Configure the location to dial on demand:
Command> set location loc_a on_demand
loc_a changed to On-Demand Dial
Set the protocol for the location:
Command> set location loc_a protocol ppp
loc_a protocol changed to ppp
Set the IP address of the location:

Note that the IP address of the location (destination) is the same as the IP address of the gateway (see Step 2).

Command> set location loc_a destination 172.16.2.1
loc_a destination changed from 0.0.0.0 to 172.16.2.1

Set the interface to send RIP packets to loc_a:
Command> set location loc_a rip broadcast
loc_a rip changed from off to broadcast, no_listen
Associate the location with a dial group:
Command> set location loc_a group 1
loc_a group number changed from 0 to 1
Set the telephone number used for dialing to the location:
Command> set location loc_a telephone 15105551212
New telephone successfully set for location loc_a
Set the username used to authenticate on the remote host:
Command> set location loc_a username prouter2
New username successfully set for location loc_a
Set the password used to authenticate on the remote host:

The username and password entered here must also be present on the remote host (in the user table, RADIUS, or other authentication mechanism).

Command> set location loc_a password ghrimpdezxt1
New password successfully set for location loc_a

Set the time period the line can be idle before the connection is dropped:
Command> set location loc_a idletime 20 minutes
loc_a idle timeout changed from 0 to 20 minutes
Set the number of dial-out ports to be used for this connection:
Command> set location loc_a maxports 1
loc_a maximumport count changed from 0 to 1
Assign the port to the dial-out group:
Command> set s1 group 1
Group number for port S1 changed from 0 to 1
Make the port available for dialing to the remote location:
Command> set s1 network dialout
Port type for S1 changed from Login to Network(dialout)
Reset the port:
Command> reset s1
Resetting port S1

Save changes and reboot:

Command> save all
Command> reboot

The show routes command issued on Router 2 now gives the following (partial) response:

Command> show routes

Destination
-----------
Gateway
-------
Flag
----
Met
---
Interface
---------

192.168.1.0
192.168.1.1
NL
1
ether0

0.0.0.0
172.16.2.1
NS
1
ptp1

172.16.2.1
172.16.2.1
HL
1
ptp2

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spider@livingston.com

Command> show routes
Destination -----------	Gateway -------	Flag ----	Met ---	Interface ---------
0.0.0.0	10.10.10.1	NS	1	ptp1
172.16.2.0	172.16.2.1	NL	1	ether0
192.168.1.1	192.168.1.1	HL	1	ptp2
192.168.1.0	192.168.1.1	ND	1	ptp2