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| General IP Routing
C
18
HAPTER
Equal-cost Multipath Routing
The routing table can only have up to 8 equal-cost multipaths for static
◆
routing and 8 for dynamic routing for a common destination. However,
the system supports up to 256 total ECMP entries in ASIC for fast
switching, with any additional entries handled by software routing.
When there are multiple paths toward the same destination with equal-
◆
cost, the system chooses one of these paths to forward each packet
toward the destination by applying a load-splitting algorithm.
A hash value is calculated based upon the source and destination IP
fields of each packet as an indirect index to one of the multiple paths.
Because the hash algorithm is calculated based upon the packet header
information which can identify specific traffic flows, this technique
minimizes the number of times a path is changed for individual flows.
In general, path changes for individual flows will only occur when a
path is added or removed from the multipath group.
P
ARAMETERS
These parameters are displayed:
ECMP Number – Sets the maximum number of equal-cost paths to the
◆
same destination that can be installed in the routing table.
(Range: 1-8; Default: 8)
W
I
EB
NTERFACE
To configure the maximum ECMP number:
Click IP, Routing, Routing Table.
1.
Select Configure ECMP Number from the Action List.
2.
Enter the maximum number of equal-cost paths used to route traffic to
3.
the same destination that are permitted on the switch.
Click Apply
4.
Figure 455: Setting the Maximum ECMP Number
– 758 –
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