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BLADEOS 6.5.2 Application Guide
BMD00220, October 2010 Chapter 15: Basic IP Routing 225
ECMP Static Routes
Equal-Cost Multi-Path (ECMP) is a forwarding mechanism that routes packets along multiple paths
of equal cost. ECMP provides equally-distributed link load sharing across the paths. The hashing
algorithm used is based on the source IP address (SIP). ECMP routes allow the switch to choose
between several next hops toward a given destination. The switch performs periodic health checks
(ping) on each ECMP gateway. If a gateway fails, it is removed from the routing table, and an
SNMP trap is sent.
OSPF Integration
When a dynamic route is added through Open Shortest Path First (OSPF), the switch checks the
route’s gateway against the ECMP static routes. If the gateway matches one of the single or ECMP
static route destinations, then the OSPF route is added to the list of ECMP static routes. Traffic is
load-balanced across all of the available gateways. When the OSPF dynamic route times out, it is
deleted from the list of ECMP static routes.
ECMP Route Hashing
You can configure the parameters used to perform ECMP route hashing, as follows:
sip: Source IP address (default)
dip: Destination IP address
Note – The sip, dip, and dipsip options enabled under ECMP route hashing or in port trunk
hashing (portchannel hash) apply to both ECMP and trunk features (the enabled settings are
cumulative). If unexpected ECMP route hashing occurs, disable the unwanted source or destination
IP address option set in trunk hashing. Likewise, if unexpected trunk hashing occurs, disable any
unwanted options set in ECMP route hashing.
sport: Source port
dport: Destination port
Note – Source port (sport) and/or destination port (dport) options for the ECMP route hash
(ip route ecmphash) are supported only when Layer 4 tcpl4 and/or udpl4 options are
enabled. Conversely, when tcp14 and/or udpl4 are enabled, hashing options for sport and/or
dport must also be enabled.
protocol: Layer 3 protocol
tcpl4: Layer 4 TCP port
udpl4: Layer 4 UDP port
The ECMP hash setting applies to all ECMP routes.