Alteon Application Switch Operating System Application Guide
Global Server Load Balancing
Document ID: RDWR-ALOS-V2900_AG1302 759
Some corporations use more than one ISP as a way to increase the reliability and bandwidth of their
Internet connection. Enterprises with more than one ISP are referred to as being multihomed.
Instead of multihoming a network to several other networks, BGP-based GSLB enables you to
multihome a particular piece of content (DNS information) to the Internet by distributing the IP
blocks that contain that content to several sites.
When using DNS to select the site, a single packet is used to make the decision so that the request
is not split to different locations. Through the response to the DNS packet, a client is locked into a
particular site, resulting in efficient, consistent service that cannot be achieved when the content
itself is shared.
For example, in multihoming, you can connect a data center to three different Internet providers
and have one DNS server that has the IP address 1.1.1.1. In this case, all requests can be received
via any given feed but are funneled to the same server on the local network. In BGP-based GSLB,
the DNS server (with the IP address 1.1.1.1) is duplicated and placed local to the peering point
instead of having a local network direct traffic to one server.
When a particular DNS server receives a request for a record (in this case, Alteon), it returns with
the IP address of a virtual server at the same site. This can done using the
local option (/cfg/
slb/gslb/rule 1/metric 2/gmetric local
) in the GSLB configuration. If one site is
saturated, then Alteon will fail over and deliver the IP address of a more available site.
For more information on configuring Alteon to support BGP routing, see Border Gateway Protocol,
page 125.
Verifying GSLB Operation
The following procedure is for verifying GSLB operations.
To verify GSLB operation
1. Use your browser to request the configured service (www.gslb.example.com in Figure 119 -
DNS Resolution with GSLB, page 707).
2. Examine the /info/slb and /info/slb/gslb information on each Alteon.
3. Check to see that all SLB and GSLB parameters are working as expected. If necessary, make any
appropriate configuration changes and then check the information again.
4. Examine the
/stats/slb and /stats/slb/gslb statistics on each Alteon.
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