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PowerConnect B-Series FCX Configuration Guide 865
53-1002266-01
Configuring IP parameters – Layer 2 Switches
26
NOTE
In the previous example, 209.157.22.199 is the IP address of the domain name server (default DNS
gateway address), and 209.157.22.80 represents the IP address of the NYC02 host.
FIGURE 134 Querying a Host on the newyork.com Domain
Changing the TTL threshold
The TTL threshold prevents routing loops by specifying the maximum number of router hops an IP
packet originated by the Layer 2 Switch can travel through. Each device capable of forwarding IP
that receives the packet decrements (decreases) the packet TTL by one. If a router receives a
packet with a TTL of 1 and reduces the TTL to zero, the router drops the packet.
The default TTL is 64. You can change the TTL to a value from 1 through 255.
To modify the TTL threshold to 25, enter the following commands.
PowerConnect(config)# ip ttl 25
PowerConnect(config)# exit
Syntax: ip ttl <1-255>
Configuring DHCP Assist
DHCP Assist allows a Layer 2 Switch to assist a router that is performing multi-netting on its
interfaces as part of its DHCP relay function.
DHCP Assist ensures that a DHCP server that manages multiple IP subnets can readily recognize
the requester IP subnet, even when that server is not on the client local LAN segment. The Layer 2
Switch does so by stamping each request with its IP gateway address in the DHCP discovery packet.
NOTE
Layer 3 Switches provide BootP/DHCP assistance by default on an individual port basis. Refer to
“Changing the IP address used for stamping BootP/DHCP requests” on page 840.
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[
Layer 3 Switch
Domain Name Server
nyc02
nyc01
nyc01
nyc02
207.95.6.199
newyork.com