Layer 4 Switching for Global Load Balance and Traffic Redirect (An Example - DNS Redirect)

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4

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DNS

Www.foo.com

162.113.25.20

Www.foo.com

172.168.13.10

Www.foo.com

250.178.2.2

A

B

C

Layer 4 switch

(Web Switch)

• Client DNS request for www.foo.com sent to local DNS;

• Local DNS quires upstream DNS at Site C; Web switch at Site C gets DNS request and determines that Site B is best to serve this user’s request;

• Acting as Authoritative Name Server, web switch returns Site B’s IP address to client’s local DNS;

• Local DNS server responds to client with IP addressfor Site B’s server farm;

• Client opens application session to 172.168.13.10 (Site B);Local load balancing at Site B selects best localserver.

Note: Some of current commercially available Layer 4  switches integrate DNS functionality in the switch

Layer3 IP

Network

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