7705 SAR Interfaces
120
Interface Configuration Guide
3HE 11011 AAAC TQZZA Edition: 01
3.2.14.1 Per-Flow Hashing
The 7705 SAR supports per-flow hashing for LAG and ECMP. Per-flow hashing uses
information in a packet as an input to the hash function, ensuring that any given traffic
flow maps to the same egress LAG port or ECMP path.
Depending on the type of traffic that needs to be distributed in an ECMP or LAG path,
different variables are used as the input to the hashing algorithm that determines the
selection of the next hop (ECMP) or port (LAG). The hashing result can be changed
using the options described in Per-Service Hashing, LSR Hashing, Layer 4 Load
Balancing, TEID Hashing for GTP-encapsulated Traffic, and Entropy Labels.
Table 15 summarizes the possible inputs to the hashing algorithm for ECMP and
LAG.
Fragmented packets cannot use Layer 4 UDP/TCP ports or tunnel endpoint IDs
(TEIDs). The datapath looks at IP source address and destination address only, even
if configured to use Layer 4 UDP/TCP ports or TEID.
In Table 15, the hashing inputs in the Service ID column and the inputs in the other
columns are mutually exclusive. Where checkmarks appear on both the per-service
and per-flow sides of the table, refer to the table note in the Service ID column to
determine when per-service hashing is used.
Table 15 Hashing Algorithm Inputs (ECMP and LAG)
Traffic Type Per-
Service
Per-Flow
Service ID System
IPv4
Address
1
Ingress
Port
2
Source and Destination
TEID
4
Internal
Multicast
Group ID
5
MPLS
Label
Stack
Entropy
Label
MAC
Address
IP
Address
UDP/TCP
Port
3
ECMP
IPv4 routed
✓
6
✓✓✓✓✓
IPv6 routed
✓
6
✓✓✓✓✓
MPLS LSR ✓✓
✓
7, 8
✓✓
✓
9
✓
9
MPLS MVPN
(LSR, eLER)
VPLS ✓
Epipe ✓
Apipe, Cpipe,
Fpipe, Ipipe,
Hpipe
✓
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