Tag Archives: IP helper

IP helper with ACL on SVI

Just another short post about IP helpers:

It took me last week a few minutes to figure out why my new configured IP helpers were not working.

The starting config was like:

interface Vlan6
 description Voice VLAN
 ip address
 ip access-group Voice in
 ip helper-address
 ip helper-address
 no ip redirects
 no ip unreachables
 standby 6 ip
 standby 6 timers 1 2
 standby 6 priority 110
 standby 6 preempt
ip access-list extended Voice
 permit ip host
 permit ip host
 permit ip
 permit ip any host

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IP helper

We all are familiar with the IP helper command to allow DHCP requests (broadcast) passthrough a router to get as a unicast packet to a DHCP server. Pretty easy and simple.. But the IP helper can do more!

When there is a network with multiple vlans and you need the use the good old “net send” command from Windows computers on all computers on all the VLAN’s, you have to configure the IP helper.
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