Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 139)

Brocade Virtual ADX Server Load Balancing Guide 123
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Miscellaneous options
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NOTE
CPU utilization is not collected for every packet but every second. Consequently, the throttling
decision might not always be accurate. Because of this, CPU utilization might go higher than the set
threshold in some situations.
Configuring UDP DNS count connection
When a client’s UDP DNS traffic follows a pattern such that the 4 tuples (Source IP, Destination IP,
Source Port, Dest Port) are exactly the same across multiple DNS requests, the Brocade Virtual
ADX will have an issue. This is because the 5 tuples (SIP, DIP, SP, DP and protocol) based on which
a new session is created by the Brocade Virtual ADX is no longer unique for the subsequent
connections but will match the existing connection created by the first DNS request. When the first
response is received from the real server, the session which was used by the multiple DNS
connections will be deleted as expected. This leads to the subsequent response from the real
server to not find a session and therefore will get the Layer 2 information forwarded instead of the
translation from real server to the virtual IP (VIP). This will result in DNS responses reaching the
client un-translated.
To resolve this, configure the Brocade Virtual ADX to keep a count of the number of UDP DNS
connections used by the session and to delete the session only when all the responses to this
session is received. Use the command at the global config level as shown.
Virtual ADX(config)#server dns-udp-count-connection
Syntax: [no] server dns-udp-count-connection
Dedicated next hop per VIP for reverse SLB traffic
This feature allows you to configure a default gateway for reverse SLB traffic at the Virtual server
level.
To configure a virtual server with a next hop gateway use the command shown in the following.
Virtual ADX(config)#server virtual-name-or-ip v1 10.1.1.1
Virtual ADX(config-vs-v1)#next-hop 10.1.1.100
Syntax: [no] next-hop next-hop-IPaddress
The next-hop-IPaddress variable specifies the IP address of the nest hop gateway for the virtual
server.
NOTE
The IP address specified for the next-hop-IPaddress must be directly connected to the Brocade
Virtual ADX.
You can also configure the virtual server to allow it to fall back to its default gateway as shown in
the following.
Virtual ADX(config)#server virtual-name-or-ip v1 10.1.1.1
Virtual ADX(config-vs-v1)#next-hop-allow-fallback-to-default-gateway
Syntax: [no] next-hop-allow-fallback-to-default-gateway