Verifying Ipv4/Ipv6 Unicast Load Balancing - Cisco CRS-1 - Carrier Routing System Router Troubleshooting Manual

Chapter 13 Troubleshooting Load Balancing

Verifying IPv4/IPv6 Unicast Load Balancing

CEF load balancing for Layer 3 flows (3-tuple algorithm) is enabled by default, but Layer 4 flows are
used in this example. Using Layer 4 information has the advantage of distributing flows more evenly
over the parallel links, because it utilizes up to seven packet and platform parameters when calculating
the egress interface. The same principles apply to Layer 3 flows, except that the load balancing algorithm
checks only the source address, destination address, and router ID.
The troubleshooting process for Layer 3 and Layer 4 load balancing is described in the following
sections:
•
•
•
Configuring Layer 4 Load Balancing
The default load balancing algorithm for Cisco IOS XR is Layer 3, so first enable Layer 4 (7-tuple
algorithm):
RP/0/RP0/CPU0:P2_CRS-8# configure
RP/0/RP0/CPU0:P2_CRS-8(config)# cef load-balancing fields L4
RP/0/RP0/CPU0:P2_CRS-8 (config)# end
Checking the CEF Database
Verify that the CEF database has the expected interfaces to the test destination, 10.1.2.1:
RP/0/RP0/CPU0:P2_CRS-8# show cef ipv4 10.1.2.1 detail
Sun Sep 21 09:41:47.457 PST DST
10.1.2.1/32, version 0, internal 0x40040001 (0xa9482f74) [1], 0x0 (0xa902a9cc),
Updated Sep 19 11:52:34.493
remote adjacency to GigabitEthernet0/6/5/5
Prefix Len 32, traffic index 0, precedence routine (0)
gateway array (0xa8e9e1b4) reference count 2, flags 0x400d00, source lsd (2),
LW-LDI[type=1, refc=1, ptr=0xa902a9cc, sh-ldi=0xa9524590]
via 10.12.48.1, GigabitEthernet0/6/5/5, 4 dependencies, weight 0, class 0
via 10.12.44.1, GigabitEthernet0/6/5/6, 4 dependencies, weight 0, class 0
via 10.12.40.1, GigabitEthernet0/6/5/7, 4 dependencies, weight 0, class 0
OL-21483-02
Configuring Layer 4 Load Balancing
Checking the CEF Database
Verifying Load Balancing
[0 type 4 flags 0x4101000 (0xa9524590) ext 0x0 (0x0)]
next hop 10.12.48.1
remote adjacency
local label 16071
next hop 10.12.44.1
remote adjacency
local label 16071
next hop 10.12.40.1
remote adjacency
local label 16071
Load distribution: 0 1 2 (refcount 0)
Hash OK Interface
0 Y GigabitEthernet0/6/5/5
1 Y GigabitEthernet0/6/5/6
2 Y GigabitEthernet0/6/5/7
Configuration Examples for Troubleshooting Load Balancing
labels imposed {None}
labels imposed {None}
labels imposed {None}
Address
remote
remote
remote
Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
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