Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 676)

For the flow control solution, enable flow control either on the ports receiving the traffic from end-
devices (servers or personal computers) and the connected end-device itself, or enable flow control on
the port-channel as shown in the following example.
switch(conf-if-te-1/0/24)# interface port-channel 100
switch(config-Port-channel-100)# qos flowcontrol tx on rx on
Once flow control is enabled, enter the show qos rcv-queue interface tengigabitethernet command
again and check the output. It should no longer be reporting packet drops. If the packet drops continue
or the ingress rate is considerably lower than expected, contact your switch support provider for further
investigation.
We recommend enabling asymmetric flow control with Brocade VDX switches. For any two adjacent
devices, one device should have Rx ON and Tx OFF, while the other device should have Rx OFF and
Tx ON.
Refer to Congestion control and queuing on page 344 for further details about congestion control.
ACL limits issues
If you keep within the supported limits of ACL usage as shown in the table below, you are unlikely to
run into system limits issues. ACLs should instantiate quickly and correctly.
ACL limits per switch in VCS mode TABLE 100
Feature Limit
Number of standard or extended ACLs created but not applied 512
Number of Layer 3 standard or extended ACLs created but not applied 512
Number of rules per standard or extended ACL 2048
Maximum number of Layer 2 or Layer 3 standard or extended ACL rules 100k
Number of physical interfaces on which an ACL is applied concurrently 48(60 in standalone mode)
Number of VLAN interfaces on which ACL is applied concurrently 100
Number of ACL counters 252
Number of TCAM table entries 1000
Number of ACL rules 6000
Number of applied, co-existing standard and extended ACLs 50
In addition, up 30,720 MAC addresses are supported.
As you approach or exceed combinations of these limits, it is possible you might encounter slow
instantiation of ACL rules, process exceptions, or ACL failure due to MAC learning issues.
Delays of several minutes can occur in the instantiation of ACL rules and counters if the number of
ACLs or VLANs is excessive. The L2SYS process message queue can become full, or CPU context
switching and process scheduling can increase to the point that ACL instantiation proceeds slowly.
Periodic monitoring with the show statistics access-list mac command will show not more than 252
ACL rules with a nonzero and incrementing frame count for rules that are correctly instantiated and
have hardware counters allocated.
ACL limits issues
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