Cisco Sg3008 Manual

IP Configuration
IPv4 Management and Interfaces
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  275
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-Delayed—The assignment of the IP address is delayed for 60 second if 
DHCP Client is enabled on startup in order to give time to discover DHCP 
address.
-Not Received—Relevant for DHCP Address. When a DCHP Client starts 
a discovery process, it assigns a dummy IP address 0.0.0.0 before the 
real address is obtained. This dummy address has the...

IP Configuration
IPv4 Management and Interfaces
276 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 
17
To define an IP static route:
STEP 1Click IP Configuration > IPv4 Management and Interfaces > IPv4 Routes.
STEP  2Click Add.
STEP  3Enter values for the following fields:
•Destination IP Prefix—Enter the destination IP address prefix.
•Mask—Select and enter information for one of the following:
-Network Mask—The IP route prefix for the destination...

IP Configuration
IPv4 Management and Interfaces
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  277
17
 
NOTEIn Layer 2 mode, the IP, MAC address mapping in ARP Table is used by the device 
to forward traffic originated by the device. In Layer 3 mode, the mapping 
information is used for Layer 3 routing as well as to forward generated traffic. 
To define the ARP tables:
STEP 1Click IP Configuration > IPv4 Management and Interfaces > ARP.
STEP  2Enter...

IP Configuration
IPv4 Management and Interfaces
278 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 
17
For devices in Layer 2 mode, there is only one directly-connected IP subnet, 
which is always in the management VLAN. All the static and dynamic 
addresses in the ARP Table reside in the management VLAN.
Interface—For devices in Layer 3 system mode, an IPv4 interface can be 
configured on a port, LAG or VLAN. Select the desired interface from the...

IP Configuration
IPv4 Management and Interfaces
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  279
17
 
UDP Relay/IP Helper
The UDP Relay/IP Helper feature is only available when the device is in Layer 3 
system mode. Switches do not typically route IP Broadcast packets between IP 
subnets. However, if this feature enables the device to relay specific UDP 
Broadcast packets, received from its IPv4 interfaces, to specific destination IP 
addresses.
To...

IP Configuration
IPv4 Management and Interfaces
280 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 
17
An untrusted port is a port that is not allowed to assign DHCP addresses. By 
default, all ports are considered untrusted until you declare them trusted (in the 
DHCP Snooping Interface Settings page).
DHCPv4 Relay
DHCP Relay relays DHCP packets to the DHCP server. 
DHCPv4 in Layer 2 and Layer 3
In Layer 2 system mode, the device relays DHCP messages...

IP Configuration
IPv4 Management and Interfaces
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  281
17
 
•DHCP Insertion - Add Option 82 information to packets that do not have 
foreign Option 82 information.
•DHCP Passthrough - Forward or reject DHCP packets that contain Option 
82 information from untrusted ports. On trusted ports, DHCP packets 
containing Option 82 information are always forwarded.
The following table shows the packet flow through...

IP Configuration
IPv4 Management and Interfaces
282 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 
17
The following describes how DHCP request packets are handled when both 
DHCP Snooping and DHCP Relay are enabled:  Option 82 
Insertion 
DisabledPacket is sent 
without Option 
82Packet is sent 
with the 
original 
Option 82Relay – 
inserts Option 
82
Bridge – no 
Option 82 is 
insertedRelay – 
discards the 
packet
Bridge – 
Packet is sent 
with the...

IP Configuration
IPv4 Management and Interfaces
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  283
17
 
The following describes how DHCP Reply packets are handled when DHCP 
Snooping is disabled: Option 82 
Insertion 
EnabledRelay – is sent 
with Option 82
Bridge – Option 
82 is added
(if port is 
trusted, 
behaves as if 
DHCP Snooping 
is not enabled)Packet is 
sent with the 
original 
Option 82Relay – is sent 
with Option 82
Bridge – 
Option 82 is...

IP Configuration
IPv4 Management and Interfaces
284 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 
17
Option 82 
insertion 
disabledPacket is sent 
without 
Option 82Packet is sent 
with the 
original 
Option 82Relay – 
discards 
Option 82
Bridge – 
Packet is sent 
without 
Option 82Relay – 
1.  I f  r e p l y  
originates in 
device, 
packet is sent 
without 
Option 82
2. If reply 
does not 
originate in 
device, 
packet is 
discarded
Bridge –...