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bbear2
Premium
join:2003-10-06
94045
kudos:5

ARP Binding vs. DHCP Address Reservation

Anyone know the difference between ARP Binding and DHCP IP Address Reservation? They both seem to do the same thing. Are they meant to be used together or separately?


Bink
Villains... knock off all that evil

join:2006-05-14
Castle Rock, CO
kudos:4

ARP binding puts a static IP to MAC address entry in a device’s ARP table. DHCP reservations allow a device on the network to always get the same IP assignment when making DHCP requests. They are not really related.


bbear2
Premium
join:2003-10-06
94045
kudos:5

ok Thanks. What's the benefit of putting a static IP to MAC address in an ARP table? Why would someone want to do this?


LLigetfa

join:2006-05-15
Fort Frances, ON
kudos:1

1 recommendation

reply to bbear2

Some devices need to know their own IP address and don't always behave as one might expect with a static ARP. A static ARP can reduce ARP requests and mitigate ARP poisoning but is no substitute for reserved IPs.
--
Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey



clarknova

join:2010-02-23
Grande Prairie, AB
kudos:7
Reviews:
·TekSavvy DSL

1 recommendation

reply to bbear2

ARP binding can be used to prevent people from changing their IP address on your network, and can therefore be used in conjunction with static IP addresses to enforce network policies.

As an example, suppose you are a service provider and you want to prevent unauthorized devices from connecting to your network. Assign each device a static IP, then use ARP binding to prevent a given device from changing its IP address, or an unrecognized device from connecting.

I can't think of a situation where you would use ARP binding without static IP addressing.
--
db


LLigetfa

join:2006-05-15
Fort Frances, ON
kudos:1

1 recommendation

said by clarknova:

I can't think of a situation where you would use ARP binding without static IP addressing.

I may temporarily static ARP a device so that I can communicate with it if it doesn't have an IP or has an IP that is off-net. I do it so that I can get into the config to then give it a proper static IP.

Sometime it works, sometime not.
--
Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey


clarknova

join:2010-02-23
Grande Prairie, AB
kudos:7
Reviews:
·TekSavvy DSL

1 recommendation

said by LLigetfa:

I may temporarily static ARP a device so that I can communicate with it if it doesn't have an IP or has an IP that is off-net.

Interesting. For off-net devices I've always just assigned an alias to my own NIC on the same net as the device I'm trying to reach. I don't know that I've ever needed to reach a device that has no IP address, but this is an interesting idea.
--
db