Dell FCX624-S Laptop User Manual


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PowerConnect B-Series FCX Configuration Guide 817
53-1002266-01
Configuring IP parameters – Layer 3 Switches
26
PowerConnect(config)# ip source-route
Enabling support for zero-based IP subnet broadcasts
By default, the Layer 3 Switch treats IP packets with all ones in the host portion of the address as IP
broadcast packets. For example, the Layer 3 Switch treats IP packets with 209.157.22.255/24 as
the destination IP address as IP broadcast packets and forwards the packets to all IP hosts within
the 209.157.22.x subnet (except the host that sent the broadcast packet to the Layer 3 Switch).
Most IP hosts are configured to receive IP subnet broadcast packets with all ones in the host
portion of the address. However, some older IP hosts instead expect IP subnet broadcast packets
that have all zeros instead of all ones in the host portion of the address. To accommodate this type
of host, you can enable the Layer 3 Switch to treat IP packets with all zeros in the host portion of
the destination IP address as broadcast packets.
NOTE
When you enable the Layer 3 Switch for zero-based subnet broadcasts, the Layer 3 Switch still treats
IP packets with all ones the host portion as IP subnet broadcasts too. Thus, the Layer 3 Switch can
be configured to support all ones only (the default) or all ones and all zeroes.
NOTE
This feature applies only to IP subnet broadcasts, not to local network broadcasts. The local network
broadcast address is still expected to be all ones.
To enable the Layer 3 Switch for zero-based IP subnet broadcasts in addition to ones-based IP
subnet broadcasts, enter the following command.
PowerConnect(config)# ip broadcast-zero
PowerConnect(config)# write memory
PowerConnect(config)# end
PowerConnect# reload
NOTE
You must save the configuration and reload the software to place this configuration change into
effect.
Syntax: [no] ip broadcast-zero
Disabling ICMP messages
Dell PowerConnect devices are enabled to reply to ICMP echo messages and send ICMP
Destination Unreachable messages by default.
You can selectively disable the following types of Internet Control Message Protocol (ICMP)
messages:
Echo messages (ping messages) – The Layer 3 Switch replies to IP pings from other IP devices.
Destination Unreachable messages – If the Layer 3 Switch receives an IP packet that it cannot
deliver to its destination, the Layer 3 Switch discards the packet and sends a message back to
the device that sent the packet to the Layer 3 Switch. The message informs the device that the
destination cannot be reached by the Layer 3 Switch.