Alteon Application Switch Operating System Application Guide
Open Shortest Path First (OSPF)
148
Document
ID:
RDWR-ALOS-V2900_AG1302
Host Routes for Load Balancing
Alteon implementation of OSPF includes host routes. Host routes are used for advertising network
device IP addresses to external networks, accomplishing the following goals:
•
Server Load Balancing (SLB) within OSPF—Host routes advertise virtual server IP
addresses to external networks. This allows standard SLB between Alteon and the server pools
in an OSPF environment. For more information on SLB, see
Server Load Balancing, page 165
and the Alteon Application Switch Operating System Command Reference.
•
ABR 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 Alteon 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.
•
ABR 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, Alteon defaults to the OSPF-derived route. For a configuration example, see
Redistributing Routes into OSPF
Alteon lets you emulate an ASBR by redistributing information from other routing protocols (static,
RIP, iBGP, eBGP, and fixed routes) into OSPF. For information on ASBR, see
. For example, you can instruct OSPF to readvertise a RIP-derived route into OSPF
as an AS-External LSA. Based on this LSA, other routers in the OSPF routing domain installs an
OSPF route.
Use the following command to redistribute a protocol into OSPF:
•
protocol name is static, RIP, iBGP, eBGP, or fixed. By default, these protocol routes are not
redistributed into OSPF.
Use one of the following three methods to redistribute the routes of a particular protocol into OSPF:
•
Exporting all the routes of the protocol
•
Using route maps
Route maps allow you to control the redistribution of routes between routing domains. For
conceptual information on route maps, see
.
•
Exporting all routes of the protocol except a few selected routes
Each of these methods is discussed in detail in the following sections.
Note:
Alteon does not redistribute Layer 3 interface IPv6 addresses when the address has a prefix
length of 128.
>> /cfg/l3/ospf/redist <
protocol name
>
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