Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 619
53-1002269-02
Configuring IP parameters – Layer 2 Switches
21
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 – 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.
By allowing multiple subnet DHCP requests to be sent on the same wire, you can reduce the
number of router ports required to support secondary addressing as well as reduce the number of
DHCP servers required, by allowing a server to manage multiple subnet address assignments.
FIGURE 102 DHCP requests in a network without DHCP Assist on the Layer 2 Switch
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[
Layer 3 Switch
Domain Name Server
nyc02
nyc01
nyc01
nyc02
207.95.6.199
newyork.com