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Denial of service
An attacker can send a fraudulent ARP messages to a client to associate a false MAC address with the
gateway address, which would blackhole all internet-bound packets from the client.
NOTE: Dynamic ARP inspection (DAI) uses entries in the L2SysFlow CAM region, a sub-region of SystemFlow. One CAM
entry is required for every DAI-enabled VLAN. You can enable DAI on up to 16 VLANs on a system. However, the
ExaScale default CAM profile allocates only nine entries to the L2SysFlow region for DAI. You can configure 10 to 16 DAI-
enabled VLANs by allocating more CAM space to the L2SysFlow region before enabling DAI.
SystemFlow has 102 entries by default. This region is comprised of two sub-regions: L2Protocol and L2SystemFlow.
L2Protocol has 87 entries; L2SystemFlow has 15 entries. Six L2SystemFlow entries are used by Layer 2 protocols, leaving nine
for DAI. L2Protocol can have a maximum of 100 entries; you must expand this region to capacity before you can increase the
size of L2SystemFlow. This is relevant when you are enabling DAI on VLANs. If, for example, you want to enable DAI on 16
VLANs, you need seven more entries; in this case, reconfigure the SystemFlow region for 122 entries using the
layer-2 eg-
acl
value
fib
value
frrp
value
ing-acl
value
learn
value
l2pt
value
qos value system-
flow 122
command.
The logic is as follows:
L2Protocol has 87 entries by default and must be expanded to its maximum capacity, 100 entries, before L2SystemFlow can be
increased; therefore, 13 more L2Protocol entries are required. L2SystemFlow has 15 entries by default, but only nine are for
DAI; to enable DAI on 16 VLANs, seven more entries are required. 87 L2Pr 13 additional L2Pr 15 L2SystemFlow
+ 7 additional L2SystemFlow equals 122.
Configuring Dynamic ARP Inspection
To enable dynamic ARP inspection, use the following commands.
1.
Enable DHCP snooping.
2.
Validate ARP frames against the DHCP snooping binding table.
INTERFACE VLAN mode
arp inspection
Examples of Viewing the ARP Information
To view entries in the ARP database, use the
show arp inspection database
command.
Dell#show arp inspection database
Protocol Address Age(min) Hardware Address Interface VLAN CPU
---------------------------------------------------------------------
Internet 10.1.1.251 - 00:00:4d:57:f2:50 Te 1/2 Vl 10 CP
Internet 10.1.1.252 - 00:00:4d:57:e6:f6 Te 1/1 Vl 10 CP
Internet 10.1.1.253 - 00:00:4d:57:f8:e8 Te 1/3 Vl 10 CP
Internet 10.1.1.254 - 00:00:4d:69:e8:f2 Te 1/5 Vl 10 CP
Dell#
To see how many valid and invalid ARP packets have been processed, use the
show arp inspection statistics
command.
Dell#show arp inspection statistics
Dynamic ARP Inspection (DAI) Statistics
---------------------------------------
Valid ARP Requests : 0
Valid ARP Replies : 1000
Invalid ARP Requests : 1000
Invalid ARP Replies : 0
Dell#
Bypassing the ARP Inspection
You can configure a port to skip ARP inspection by defining the interface as trusted, which is useful in multi-switch environments.
ARPs received on trusted ports bypass validation against the binding table. All ports are untrusted by default.
Dynamic Host Configuration Protocol (DHCP)
297
Содержание S4048-ON
Страница 1: ...Dell Configuration Guide for the S4048 ON System 9 9 0 0 ...
Страница 146: ...Figure 14 BFD Three Way Handshake State Changes 146 Bidirectional Forwarding Detection BFD ...
Страница 477: ...Figure 68 Inspecting Configuration of LAG 10 on ALPHA Link Aggregation Control Protocol LACP 477 ...
Страница 480: ...Figure 70 Inspecting a LAG Port on BRAVO Using the show interface Command 480 Link Aggregation Control Protocol LACP ...
Страница 481: ...Figure 71 Inspecting LAG 10 Using the show interfaces port channel Command Link Aggregation Control Protocol LACP 481 ...
Страница 522: ...Figure 87 Configuring Interfaces for MSDP 522 Multicast Source Discovery Protocol MSDP ...
Страница 523: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 523 ...
Страница 524: ...Figure 89 Configuring PIM in Multiple Routing Domains 524 Multicast Source Discovery Protocol MSDP ...
Страница 528: ...Figure 91 MSDP Default Peer Scenario 1 528 Multicast Source Discovery Protocol MSDP ...
Страница 529: ...Figure 92 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 529 ...
Страница 530: ...Figure 93 MSDP Default Peer Scenario 3 530 Multicast Source Discovery Protocol MSDP ...
Страница 633: ...Policy based Routing PBR 633 ...
Страница 777: ...Figure 119 Single and Double Tag TPID Match Service Provider Bridging 777 ...
Страница 778: ...Figure 120 Single and Double Tag First byte TPID Match 778 Service Provider Bridging ...