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LAN/WAN Routing Protocols in Orbitor Networks

Article Number: I005
Article Type: Info
Modified: November 18, 1998

SUMMARY

The Orbitor router products can be used in a variety of network applications. The features available in the Orbitor product line are present to accommodate these applications but sometimes it is not always clear when to use a particular feature over another.

This article will focus on the LAN and WAN IP Routing protocols available in the Orbitor. It will present a description of each, the values that are best used for specific applications, and the ramifications of an incorrect selection.

Due to the technical nature of this article, the reader should understand the concepts of routing and its use in typical network applications.

MORE INFORMATION

Each section in this article relates to a feature parameter available in the Orbitor. Contained with each parameter are the available settings, and the appropriate setting for a specific application.

LAN Routing Protocol

The LAN Routing Protocol option, available on the IP Routing Menu, defines the type of IP routing protocol to be used on the LAN interface. The Orbitor may be configured to use different types of IP routing protocols on each of it's available interfaces, and therefore the setting of this parameter does not affect the settings of the WAN IP Routing protocol.

	Default: [rip1_compatible]
	Choices: none, rip1, rip1_compatible, rip2

none

When the routing protocol is set to none, the Orbitor will operate as an IP router but will NOT participate in the exchange of RIP messages between the other IP routers in the network. All IP routing is accomplished by using operator-configured, statically-defined routes in the routing table. This means that all routes within the network must be manually entered in the routing table in order for the Orbitor to know where to send each packet that passes through its interfaces.

rip1

When the routing protocol is defined as rip1, the Orbitor will operate as a RIP1 IP router. All routing information will be sent and received via broadcast RIP packets.

This is still the most common routing protocol used extensively in private IP-based networks.

rip1_compatible

When the routing protocol is defined as rip1_compatible, the Orbitor will operate as a RIP2 IP router in broadcast mode. All routing information will be sent via broadcast RIP2 packets. Routing information may be received as broadcast RIP1, broadcast RIP2, or multicast RIP2.

For clarity, a RIP1 device will not receive a multicast RIP2 packet, since it is not addressed to the proper RIP1 address. However, a RIP1 device will be able to receive a broadcast RIP2 packet and be able to interpret those fields that are compatible with RIP1. This allows for a level of interoperability between RIP1 and RIP2 devices.

Rip1_compatible is a reasonable choice in a situation where you need to accommodate the subnetting flexibility's of your network, while still supporting some older routers or servers on your LAN. However, although the use of rip1_compatible should not pose a problem for older router implementations that follow the rip1 protocol specification properly, it may well not work properly with them

If you do experience a routing problem where a host, router or server is not receiving the appropriate routing information from the Orbitor network, and the host, router or server is supporting rip1, change the Orbitor to rip1 instead.

rip2

When the routing protocol is defined as rip2, the Orbitor will operate as a RIP2 IP router. All routing information will be sent via multiast RIP2 packets. Routing information may be received as broadcast RIP2 or multicast RIP2.

Rip2 propagates subnetting information for each route in the network. This allows rip2 to accommodate network environments that contain differing sized subnets (often called Variable Length Subnets - VLSM). In contrast, Rip1 may only be used effectively in networks where all subnets are created with the same mask size.

Rip Mode

The RIP Mode option defines how the Orbitor will participate in RIP IP routing messages over the LAN.

When the RIP mode is set to both, the Orbitor will send and receive RIP routing messages over the link to this remote site.

When the RIP mode is set to send_only, the Orbitor will only send RIP routing messages over the link to this remote site.

When the RIP mode is set to receive_only, the Orbitor will only receive RIP routing messages over the link to this remote site.

Due to the special nature of this parameter, it most often is set to both. However, by selecting one value or the other will allow you to control if routes are propagated in a specific direction. When used in concert with the WAN RIP mode option, the router may now serve as a means of performing selective network/route isolation.

LAN Routing Protocol Considerations

The LAN Routing Protocol that you will select for your specific application will be dependent upon your specific needs as well as the other routers and hosts/servers that may be present in your network. Selecting the correct value is important to the success of your network.

In general, this value selected will have to accommodate the lowest-common denominator in your network. If all other routers in your network only understand RIP1, for example, then this is the value that must be selected on the Orbitor.

None may be the only option when installing an Orbitor product into an environment where the routing protocol is unsupported by the Orbitor.

Rip1 is a wise choice when the routing support of older products do not handle any other protocol option.

Rip1_compatible is a good choice when you need to take advantage of Rip2 functionality, while still supporting older routers, hosts, or servers on the network. Please note that not all routers support rip1 properly and therefore will reject rip1_compatible routing messages.

Rip2 is a wise choice in a situation where Variable-Length Subnetting is in place.

WAN Routing Protocols

In the Remote Site configuration, located in the IP Parameters -- IP Routing menu, is the Routing Protocol option. This option contains the same values as the LAN Routing Protocol above, and therefore will not be re-iterated here. Please consult the LAN Routing Protocol section for additional details.

The one parameter that will have a key effect on the operations of the router in your application, though, is Triggered Rip and the following section describes its use.

Triggered Rip

Triggered Rip defines when routing updates are propagated across the WAN. The Triggered RIP option disables or defines the type of triggered RIP to use on the link to this remote site.

	Default: [disabled]
	Choices: disabled, standard, link_up_only

Disabling this option will cause the RIP routing tables to be transmitted every 60 seconds as is defined by the RIP standard. This option is most useful when the router is being used in a typical "leased-line" application where the links are permanently established.

Entering standard enables triggered RIP; the Orbitor will only send RIP messages over the link to this remote site when the routing information has actually changed. This option is most useful when you wish to reduce RIP routing traffic, but when you need to ensure that the routing changes are propagated immediately.

Entering link_up_only enables triggered RIP; the Orbitor will only send RIP messages over the link to this remote site when the routing information has actually changed and the link is currently up and connected to its remote partner.

The use of this option is recommended when you have enabled the Connection Management Control Protocol (CMCP) to perform protocol spoofing over ISDN. You should not use either standard or disable this option, as these setting will have an affect on the ISDN call charges encountered.

When using this option, if the link is down due to suspension (the link was idle for the prescribed period of time), the routing information will be queued and then sent the next time the link is activated/connected to send user data. Using this mode will ensure that ISDN calls are only established when real user data is available to send, reducing call charges.

When triggered RIP is enabled, if the remote site router refuses to negotiate triggered RIP on the initial connection, this router will attempt to negotiate triggered RIP for 5 minutes. During the 5 minutes, this router will use normal RIP and SAP. If triggered RIP has not been negotiated after the 5 minutes, this router will fall back to using normal RIP and SAP.

Auto Default Route

The Auto Default Route option allows a default IP route to be added to the routing tables when a connection is established to the defined remote site. When the link to this remote site goes down, the auto default route will be automatically removed from the routing table.

	Default: [disabled]

This feature is very useful in Internet Access applications when all other network routes are available through this router. In applications where there are many other routers present on the connected LAN, you should consider leaving this parameter disabled, as enabling it may not provide the desired results.

REFERENCES

For further information, please refer to the Orbitor Reference Manual, or contact Support Services directly.§

Copyright © 1998 Develcon Electronics Ltd.  All Rights Reserved.