Ip (Ipv4 And Ipv6) - Juniper EX2200 Hardware Manual

Network Interfaces for EX4300 Switches

IP (IPv4 and IPv6)

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The hashing algorithm makes hashing decisions based on values in various packet fields,
as well as on some internal values like source port ID and source device ID. The packet
fields used by the hashing algorithm varies by the packet's EtherType and, in some
instances, by the configuration on the switch. The hashing algorithm recognizes the
following EtherTypes:
IP (IPv4 and IPv6)
MPLS
MAC-in-MAC
Traffic that is not recognized as belonging to any of these EtherTypes is hashed based
on the Layer 2 header. IP and MPLS traffic are also hashed based on the Layer 2 header
when a user configures the hash mode as Layer 2 header.
You can configure some fields that are used by the hashing algorithm to make traffic
forwarding decisions. You cannot, however, configure how certain values within a header
are used by the hashing algorithm.
Note the following points regarding the hashing algorithm:
The fields selected for hashing are based on the packet type only. The fields are not
based on any other parameters, including forwarding decision (bridged or routed) or
egress LAG bundle configuration (Layer 2 or Layer 3).
The same fields are used for hashing unicast and multicast packets. Unicast and
multicast packets are, however, hashed differently.
The same fields are used by the hashing algorithm to hash ECMP and LAG traffic, but
the hashing algorithm hashes ECMP and LAG traffic differently. The different hashing
ensures that traffic is not polarized when a LAG bundle is part of the ECMP next-hop
path.
The same fields are used for hashing regardless of whether the switch is or is not
participating in a mixed or non-mixed Virtual Chassis or Virtual Chassis Fabric (VCF).
The fields used for hashing by each EtherType as well as the fields used by the Layer 2
header are discussed in the following sections.
Payload fields in IPv4 and IPv6 packets are used by the hashing algorithm when IPv4 or
IPv6 packets need to be placed onto a member link in a LAG bundle or sent to the
next-hop device when ECMP is enabled.
The hash mode is set to Layer 2 payload field, by default. IPv4 and IPv6 payload fields
are used for hashing when the hash mode is set to Layer 2 payload.
If the hash mode is configured to Layer 2 header, IPv4, IPv6, and MPLS packets are hashed
using the Layer 2 header fields. If you want incoming IPv4, IPv6, and MPLS packets hashed
by the source MAC address, destination MAC address, or EtherType fields, you must set
the hash mode to Layer 2 header.
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