Configuring IP Routing

Once connected to the remote site, the unit learns IP routes through the network as it receives RIP updates. It automatically updates the IP Routes table. You can delete unwanted routes if they are not required. You can also enter static routes that have, for some reason, not been learned.

	When routing IP over unnumbered links, static routes must be entered on this screen.

At the command prompt, enter CO RO IP to view or amend the Configured IP Routes table shown in Figure 7-3.

Figure 7-3

Configured IP Routes Table

The entries in this table show the following:

Target Shows the IP address of the target network.

Subnet Mask Shows the subnet mask applied to this address.

Router Shows the name of the remote router to which this route connects.

Hops Shows the number of hops (or routers through which the data is passed) to reach the target.

Interface Shows the interface (port) for this route.

Flags Show information about the route as follows:

	A - Indicates an advertised route.

	S - Indicates a static route. All routes that are manually entered, or learned routes that are edited are static routes.

	P - Indicates a permanent route. This is a static route that cannot be overwritten by a better route.

	D - Indicates a dynamic route. All learned routes are dynamic routes by default.

Adding or Editing an IP Route

You can manually add an IP route or edit an existing entry in the table.

	You must have a good understanding of IP routing before attempting to manually configure routes.

To add an entry, enter ADD at the command prompt.

To edit an entry, highlight the entry to be edited and enter ED at the command prompt.

A screen similar to the one in Figure 7-4 is displayed.

	Only manually entered static routes can be made permanent. TCP/IP routers broadcast IP RIP updates every 30 seconds.

	IP routes learned over ISDN do not age, however those learned over the WAN and LAN ports do. Using the SAVE command, saves ISDN learned routes.

	A consistent IP subnet mask must be defined.

Figure 7-4

Add Routing Table Entry

The fields in this screen are:

Target The IP address of the host to which you want to connect.

Subnet Mask The subnet mask to be used on this route. A subnet mask of 255.255.255.255 allows data to be passed only to this host.

Router The name of the remote unit connecting to the target network. If the remote unit is connected to using an ISDN link, an ISDN number must be configured for this router.

Hop Count Enter the hop count to reach the target.

Advertise Route Set this field to ENABLED if this route is to be advertised as part of routing updates to other routers.

Permanent If ENABLED makes the route permanent. A permanent route is a static route that cannot be overwritten by a better router.

Deleting an IP Route

Highlight an entry and enter DEL at the command prompt. The entry is deleted from the table. If this entry was learned dynamically by the unit, it may be added upon receipt of the next RIP update unless an IP firewall has been configured to reject RIP updates for this route.

Routing IP over Unnumbered Links

A static return route must be entered into the IP routing table (CO RO IP) at each end of the link when IP is routed over unnumbered links. The static route must specify the remote LAN IP network address in the Target field and the remote unit's name in the Router and Interface fields. These routes will not be learned and need to be configured manually. Dynamic learning of routes will not be possible until this is done.

This is particularly important when you are configuring the units remotely. The return route must be entered into the IP routing table of the remote unit before routing is switched on, otherwise the return route will not be established.

Figure 7-5 shows a representation of an unnumbered link between a unit named "ciren" located in the Cirencester office and a unit named "head_office" at the Head Office site.

Configuring an Unnumbered Link

Figure 7-5

Example of an Unnumbered Link

1 .	At the command prompt, enter CO RO IP to view the Configured IP Routes table.

2 .	Enter ADD to add a new entry.

3 .	Figure 7-6 shows how the configuration for the "ciren" unit would be added to the "head_office" unit's routing table. The example network has a subnet mask of 255.255.255.0

4 .	Type [CTRL]+[E] to submit the new settings.

Figure 7-6

Adding the "ciren" Unit to the Head Office Unit Routing Table

Figure 7-7 shows the Configured IP Routes table on the "head_office" unit after the addition of the "ciren" unit.

Figure 7-7

Configured Routes Table for Head Office Unit

5 .	Save the new settings by entering SAVE

6 .	Configure the unit at the other end of the link in a similar fashion. Figure 7-8 shows an example of the Configured IP Routes table for the Cirencester office "ciren" unit when the return link to the head office unit has been added.

Figure 7-8

Configured IP Routes Table for Cirencester Office Unit