Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 146)

130 Brocade Virtual ADX Server Load Balancing Guide
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Miscellaneous options
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If you configure a vip-route-mask-length as “96” then when this VIP becomes healthy, an IPv6
subnet route with a mask length of “96” is advertised as shown.
S 2001:DB8::/96 2001:DB8::10 loopback 1 1/1
Where a user configures the vip-route-subnet-mask-length to the same values as the interface
mask length, RHI injects two subnet static routes instead of one. In this situation the user will see
two routes instead of one. For example, if the interface subnet mask length is “64” and the user
configures the vip-subnet-mask-length as “64”, two routes will be advertised as shown below.
S 2001:DB8::/65 2001:DB8::10 loopback 1 1/1
S 2001:DB8::80:0:0:0/65 2001:DB8::10 loopback 1 1/1
Please note the subnet mask length of the above routes. When the user changes the VIP subnet
mask length to and from being equal to the interface subnet mask length, the VIP static route
injected will be corrected between dual routes and a single static route. This dual route extension
was created to accommodate a larger range/number of VIP hosts within a subnet.
NOTE
One exception to the above dual route case is where value of the vip-route-subnet-mask-length
command exceeds 125. In this situation, RHI will only inject host static routes.
NOTE
Use caution while configuring the vip-route-subnet-mask-length command value. Please make sure
that the VIP subnets do not overlap with each other.
VIP RHI with dangling subnets
Normally a VIP with RHI should have an associated interface with an interface address (IPv4 or
IPv6) belonging to the VIP subnet. This means that at least one IP address belonging to the VIP
subnet is consumed by the interface and cannot be used as a public address for the VIP server and
RHI has to depend on having an associated interface.
A user who does not wish to waste one public IP address to the interface can do so without adding
any IP address in the VIP subnet. In this situation the VIP is deemed to be a “dangling VIP” (not
associated with any interface). If the user adds an IP address in the VIP subnet to an interface,
such a VIP is called a “non-dangling VIP”. The Brocade Virtual ADX supports both dangling and
non-dangling VIPs. RHI determines the mode of the VIP at the time when advertise is enabled. The
routes advertised also differ slightly in case of dangling VIPs as described in the following:
• Non-dangling VIPs: RHI will associate with the matching interface and set boundaries for the
VIP route to be advertised. In this case, RHI makes sure that it does not advertise a route
bigger than the size of the associated subnet itself. This also includes advertising of dual
routes. This configuration also allows dynamic-sym-priority to be bound with an associated
interface status.
• Dangling VIPs: RHI will use the VIP-route-subnet-mask-length and blindly advertise a static
route of that size. A user will see static routes with the next hop address as 255.255.255.255
in case of IPv4 VIP and :: (invalid IPv6 address) for an IPv6 VIP. In case of IPv4 the port value of
the route shows “drop” and for IPv6 the port is “null”. In this mode dynamic-sym-priority is not
bound to interface status.