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Manual Chapter: Routes
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The BIG-IP® system must communicate with other routers, servers, and firewalls in a networked environment. Before you put the BIG-IP system into production, we recommend that you carefully review the router and server configurations in your network. By doing so, you can properly configure routing on the BIG-IP system, and you can adjust the routing configurations on other network devices to include various BIG-IP system IP addresses. Depending on how you configure routing, the BIG-IP system can forward packets to a specified network device (such as a next-hop router or a destination server), or the system can drop packets altogether.
Due to its IP routing (Layer 3) capabilities and its need to process both user application traffic (for load balancing and health monitoring) and administrative traffic, the BIG-IP system processes two types of routes:
Management routes
The BIG-IP system stores and retrieves information about management routes. Management routes are routes that the BIG-IP system uses to forward traffic through the special management interface.
TMM routes
The BIG-IP system stores and retrieves IP routing information about TMM switch routes. TMM switch routes are routes that the BIG-IP system uses to forward traffic through the TMM switch interfaces instead of through the management interface.
To configure and manage routes, log in to the BIG-IP Configuration utility, and on the Main tab, expand Network, and click Routes.
Important: To add routes for route domains other than route domain 0, review the information in Chapter 23, Route Domains.
The purpose of the TMM routing table is to store essential routing information for traffic passing through the TMM system. The BIG-IP system creates a routing table automatically when you configure its local interfaces. Once the routing table is created, there are two ways to maintain it:
You can use one or more dynamic routing protocols to automatically update entries on a regular basis. These entries are known as dynamic route entries. For information on configuring dynamic routing, see Chapter 24, Advanced Routing Modules.
On a typical router, the gateway that you define within a route entry is the address for a next-hop router. On the BIG-IP system, however, the gateway that you specify can be any of four different resource types:
Important: Only users with either the Administrator or Resource Administrator user role can create and manage route entries on the BIG-IP system.
Using the Configuration utility, you can view the list of static entries on the BIG-IP system. You can view only those routes that reside in administrative partitions to which you have access.
For example, if a user account with the Manager user role has access to Partition_A, this user can see only those routes that reside in Partition_A and Common. Users with the Administrator or Resource Administrator user role, however, have access to all partitions and can therefore see all routes on the BIG-IP system.
Figure 16.1 shows an example of a list containing both default and standard route entries.
Destination IP address
For the destination address, you can see either a default entry, a host destination, or a network address.
Netmask
This is the netmask of the destination address. No netmask appears for the default route.
Partition
This is the name of the administrative partition in which the route object resides.
Route domain ID
This is the ID of the route domain to which the route pertains. The ID Partition Default Route Domain refers to route domain 0, which is the default route domain for partition Common. Unless you are explicitly using the route domains feature of the BIG-IP system, you can ignore this column. For information about route domains, see Chapter 23, Route Domains.
Resource type
The resource type appears as either Gateway, Pool, VLAN, or Reject.
Resource name
The resource name is either a next-hop-router (gateway) address, a pool name, or a VLAN name.
You use the Type property to specify the type of static route that you want to define in the routing table. A static route that you add to the TMM routing table can be either of two types: a standard (non-default) route or a default route. On the screen for creating a static route entry, a non-default route is simply called a route. A default route is called a default gateway.
You add a standard route when you want to provide a route that either corresponds directly to the destination IP address of a packet, or specifies the network portion of the destination IP address of a packet. You add a default gateway when you want to provide the route that the BIG-IP system should use for forwarding packets when no other entry in the routing table matches the destination IP address of the packet. You can add two types of default gateway routes: Default Gateway IPv4 and Default Gateway IPv6.
The Route Domain ID setting appears only when you set the Type setting to Default Gateway. Unless you are using the route domains feature of the BIG-IP system, you can ignore this setting. For information about route domains, see Chapter 23, Route Domains.
You use the Destination setting when you want to define a standard (non-default) route. If you are defining a default route, this property is unavailable.
Using the Destination setting, you can specify either an individual destination IP address, to match the destination IP address of a packet, or the network portion of a destination IP address of a packet.
For example, if you want the BIG-IP system to forward packets destined for IP address 192.0.2.225, you could specify one of the following addresses:
192.0.2.225
In this case, the BIG-IP system forwards any packet with the exact destination IP address of 192.0.2.225 to the gateway that you define in that routing table entry.
192.0.2.0
In this case, the BIG-IP system forwards to the gateway any packets with a destination IP address that includes the network ID 192.0.2.
You use the Netmask property when you want to define a non-default route. If you are defining a default route, this property is unavailable.
Using the Netmask property, you specify the netmask for the destination IP address that you defined with the Destination property. The purpose of the netmask is to indicate whether the IP address defined in the Destination property is a host address or a network address.
Any entry that you add to the TMM routing table includes either a next-hop router, a pool of routers, or a VLAN as the gateway, or resource, through which to send traffic. To specify a resource in a routing table entry, you use the Resource setting. You can also instruct the BIG-IP system to reject packets for the specified destination IP address. Table shows the resource types you can specify when adding a route.
If you know that a server in a load balancing pool is on the same internal network as the BIG-IP systems next-hop router (gateway), you can specify the gateway address.
A common scenario when adding a route is to define the gateway as a pool of routers instead of a single next-hop router. For example, you can create a pool named router_pool, and specify the pool as the gateway for the default route. You can see this route in the first entry of Figure 16.1.
Before you specify a pool of routers as a gateway in the routing table, however, you must create the pool, using the same Configuration utility screens that you use for creating a pool of load balancing servers.
For more information on creating a pool, see the Configuration Guide for BIG-IP® Local Traffic Manager. For background information on using a pool of routers as a gateway, see About TMM routes.
The gateway address in a routing entry can also be a VLAN//tunnel name. You can select a VLAN/tunnel name as a resource when the destination address you specify in the routing entry is a network address. Using a VLAN/tunnel name as a resource implies that the specified network is directly connected to the BIG-IP system. In this case, the BIG-IP system can find the destination host simply by sending an ARP request to the hosts in the specified VLAN, thereby obtaining the destination hosts MAC address. Then, the BIG-IP system simply checks the VLANs Layer 2 forwarding table to determine the correct interface through which to forward the packet.
Sometimes, you might want the BIG-IP system to drop any packets destined for the IP address specified as the destination in a routing entry. In this case, you simply select Reject as the value for the Resource setting when creating a route entry.
Figure 16.2, shows an example of using the Configuration utility to specify a default route.
Figure 16.3 shows an example of using the Configuration utility to specify a standard route.
After you have configured the TMM routing table on the BIG-IP system, you might want to consider some other routing issues. For example, it is customary to ensure that the routers on the network have information about the various IP addresses for the BIG-IP system, such as virtual server addresses, self IP addresses for VLANs, and so on. Fortunately, the BIG-IP system eases this task by sending gratuitous Address Resolution Protocol (ARP) messages to other routers on the network, to notify them of BIG-IP system IP addresses. For more information on ARP and the BIG-IP system, see Chapter 26, Address Resolution Protocol.
The beginning of this chapter explained that there are two types of entries in the BIG-IP system routing table: static entries and dynamic entries. The chapter then described how to add and delete static entries. If you want the system to add entries dynamically, you can use one of the advanced routing modules. For more information, see Chapter 24, Advanced Routing Modules.
When configuring routes on a BIG-IP system, it is helpful to understand the differences between management routes and TMM routes. This is because there are certain administrative tasks, such as a system installation, that you should perform only when the TMM is not running. In those cases, the BIG-IP system uses the default management route for processing that traffic.
The section in Chapter 7, BIG-IP Platform Properties, that describes the management interface.
Appendix B, Understanding Core System Services, which suggests some of the administrative tasks that you should perform only when the TMM service is stopped.
The guide titled BIG-IP® Systems: Getting Started Guide for procedures on configuring the management interface.
Also, verify that you have defined a default TMM route in the main TMM routing table. Defining a default TMM route prevents high volumes of administrative traffic generated by the BIG-IP system from using the management interface. For more information, see About TMM routes.
Part of managing routes on a network is making sure that destination servers on the network can route responses to the BIG-IP system. To do this, you should configure the default route on each load balancing server to forward responses to the BIG-IP system.
Configuring the default route on your destination servers is a typical network configuration task. To configure the default route on your destination servers, see the product documentation from your server vendor.
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