Dell S4820T, Configuration Manual

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CPU
Queue
Weights Rate (pps) Protocol
3 4 400 sFlow, L3 MTU Fail
frames
4 127 2000 IPC/IRC, VLT Control
frames
5 16 300 ARP Request, NS, RS, iSCSI OPT Snooping
6 16 400 ICMP, ARP Reply, NTP, Local terminated L3, NA, RA,ICMPv6
(other Than NDP and MLD)
7 64 400 xSTP, FRRP, LACP,
802.1x,ECFM,L2PT,TRILL,
Open flow
8 32 400 PVST, LLDP, GVRP,
FCOE, FEFD, Trace flow
9 64 600 OSPF, ISIS, RIPv2, BGP
10 32 300 DHCP, VRRP
11 32 300 PIM, IGMP, MSDP, MLD
Catch-All Entry for IPv6 Packets
Dell Networking OS currently supports configuration of IPv6 subnets greater than /64 mask length, but
the agent writes it to the default LPM table where the key length is 64 bits. The device supports table to
store up to 256 subnets of maximum of /128 mask lengths. This can be enabled and agent can be
modified to update the /128 table for mask lengths greater than /64. This will restrict the subnet sizes to
required optimal level which would avoid these NDP attacks. The IPv6 stack already supports handling of
>/64 subnets and doesn’t require any additional work. The default catch-all entry is put in the LPM table
for IPv4 and IPv6. If this is included for IPv6, you can disable this capability by using the
no ipv6
unknown-unicast
command. Typically, the catch-all entry in LPM table is used for soft forwarding and
generating ICMP unreachable messages to the source. If this is in place then irrespective of whether it is
</64 subnet or >/64 subnet, it doesn’t have any effect as there would always be LPM hit and traffic are
sent to CPU.
Unknown unicast L3 packets are terminated to the CPU CoS queue which is also shared for other types
of control-plane packets like ARP Request, Multicast traffic, L3 packets with Broadcast MAC address. The
catch-all route poses a risk of overloading the CPU with unknown unicast packets. This CLI knob to turn
off the catch-all route is of use in networks where the user does not want to generate Destination
Unreachable messages and have the CPU queue’s bandwidth available for higher priority control-plane
traffic.
Configuring CoPP for OSPFv3
You can create an IPv6 ACL for control-plane traffic policing for OSPFv3, in addition to the CoPP support
for VRRPv3, BGPv6, and ICMPv6. This functionality is supported on the S4810, S4820T, S6000, MXL, and
Control Plane Policing (CoPP)
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