WebOS 10.0 Application Guide
82 Chapter 4: OSPF 212777-A, February 2002
Host Routes for Load Balancing
WebOS 10.0 implementation of OSPF includes host routes. Host routes are used for advertis-
ing network device IP addresses to external networks, accomplishing the following goals:
nServer Load Balancing (SLB) within OSPF
Host routes advertise virtual server IP addresses to external networks. This allows stan-
dard SLB between the Web switch and the server pools in an OSPF environment. For
more information on SLB, see Chapter 6, “Server Load Balancing and your WebOS 10.0
Command Reference.
nABR Load Sharing
As a second form of load balancing, host routes can be used for dividing OSPF traffic
among multiple ABRs. To accomplish this, each Web switch provides identical services
but advertises a host route for a different virtual server IP address to the external network.
If each virtual server IP address serves a different and equal portion of the external world,
incoming traffic from the upstream router should be split evenly among ABRs.
nABR Failover
Complementing ABR load sharing, identical host routes can be configured on each ABR.
These host routes can be given different costs so that a different ABR is selected as the
preferred route for each virtual server and the others are available as backups for failover
purposes.
If redundant routes via multiple routing processes (such as OSPF, RIP, BGP, or static routes)
exist on your network, the Web switch defaults to the OSPF-derived route.
For a configuration example, see “Example 4: Host Routes” on page 92.
OSPF Features Not Supported in This Release
The following OSPF features are not supported in this release:
nRedistributing routes into OSPF (WebOS 10.0 does not allow your switch to emulate an
ASBR)
nSummarizing external routes
nFiltering OSPF routes
nConfiguring equal cost route load balancing
nUsing OSPF to forward multicast routes
nConfiguring OSPF on non-broadcast multi-access networks (such as frame relay, X.25,
and ATM)