can one ethernet card support multiple ip address?

i googling it.

they say it possible.

but i think it's very dangerous. if bad guy take many ip, other people can't get ip.

my question is "does one ethernet card take multiple real ip or multiple virtual ip(one real ip)?"

if it takes multiple real ip, then how it works good?..

please advise.
thanks.

Having the right terminology helps when googling. What you are looking for is commonly referred to as "ip alias". There is a somewhat dated, but basically still valid, howto here http://www.faqs.org/docs/Linux-mini/IP-Alias.html. In recent years various distributions of linux have come up with different ways of configuring this.

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thanks.

but my question is not how to use many ip.

i want to know "can one ethernet card take many real ip?".

i think "ip alias" and router's mechanism is similar.

then host can't see my ip's alias, host see my one real ip.

What makes the difference between a real IP and an aliased IP? If you assign you ethernet card another IP, it acts as it has 2 network cards, each with its own IP. Traffic for one subnet is sent on one, traffic for the other subnet is sent on the other. The same happens with the adapter with multiple IP addresses, only the same physical plug is used.

jlinkels

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Not sure what your question is, then, or whether it might not just be a question of definition or semantics. When you set up "IP Aliasing", they are real IPs. For example, I have a server that has one interface that has a public address and multiple private addresses. We run NATing and have most of our desktops on private IPs. They can address the server on the private subnet. The server can also be accessed from the outside on its public address. Of course, this requires running a border router and a DNS server for everything to work.

There's also virtual hosting for Apache. That references the primary IP address, but the domain registration has to be set up to point to my primary IP. So, there end up being multiple domain names that resolve to the same IP address. However, if you look up the IP address, it will return my primary domain.

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Which linux distribution are you on?
http://www.cyberciti.biz/faq/bind-al...ress-in-linux/

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thanks for asking.

i understand it.

but could it make bad problem if someone deliberately take many ips?

Not really. Numbers of IPs shouldn't be a problem. They would only cause problems for themselves or within the subnet are responsible for. If they don't own the IP range or control the DNS, they aren't going to get traffic to themselves for additional IPs.

On the other hand, within a specific subnet, a misbehaving individual can cause problems. They can take or assign a fixed IP that belongs to another device and cause routing problems. I once had someone maliciously change the IP on a public printer to the same IP as our primary server. Caused no end of trouble. I was on vacation and got called. After that, I mandated that the people setting up the printers lock them down. That was in the late 1990's.