Purpose of Dual ports on NICs?

[C T]

As the title states, I am wondering what the purpose of dual ports on a NIC is. I already have some ideas but prefer certainty and a google search mainly provides a ton of advertisements to purchase one, so I'd like the scoop from you knowledgeable tech-folk, thank you.

I'm not in the market for one I'm just a tyro in the IT field and am trying to fill the gaps in my knowledge base. Thank you so much

 

[popatim]

What ideas do you already have?

 

[RealBeast]

Homework hotline? :lol:

 

[C T]

I'm just trying to learn because I have an inquisitive mind @Homework help.

What I believe the purpose of multiple ports on a NIC:
-to provide interfaces for multiple networks
-to interface other network devices such as a printer

Seems I came to the wrong place for a helpful reply, I appreciate your attempts. I shall find my answers on Google.

 

[Kewlx25]

If you need more than 1 port, then it's typically cheaper and more space efficient to have more than one port on a NIC. You can purchase NICs with upwards of 4 ports, sometimes higher for NICs with adapters. You can purchase dual port 40Gb NICs that have adapters to allow for 4 10Gb ports per 40Gb port, meaning 8 10Gb ports.

 

[C T]

Thanx Kewlx

I found some informative tidbits:

"There are a number of ways to use 2 Ethernet ports :

Two Network Connections (two subnets)

Will allow your PC to be connected to two networks at the same time.

Balance-rr (Round-Robin)

Transmit packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

Active Backup(Fail Over)

Only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. The bond’s MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. This mode provides fault tolerance.

Balance XOR

Transmit based on the selected transmit hash policy. The default policy is a simple [(source MAC address XOR’d with destination MAC address) modulo slave count]. Alternate transmit policies maybe selected via the xmit_hash_policy option. This mode provides load balancing and fault tolerance.

Broadcast

Transmits everything on all slave interfaces. This mode provides fault tolerance.

IEEE 802.3ad

Creates aggregation groups that share the same speed and duplex settings. Utilizes all slaves in the active aggregator according to the 802.3ad specification. This mode provides load balancing and fault tolerance but requires a switch that supports IEEE 802.3ad Dynamic Link Aggregation with correct LACP mode configured.

Balance-tlb (Adaptive Transmit Load Balancing)

Channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave. This mode provides load balancing and fault tolerance.

Balance-alb (Adaptive Load Balancing)

Include balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special switch support. The receive load balancing is achieved by ARP negotiation. The receive load balancing is achieved by ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond such that different peers use different hardware address for the server. This mode provides load balancing and fault tolerance."

-attributed to Iggster http://www.techpowerup.com/forums/threads/using-dual-gigabit-ethernet-ports.118632/

Here are some other good ones:
http://archive09.linux.com/feature/133849
http://www.overclockers.com/forums/showthread.php/596734-What-do-you-use-your-dual-ethernet-ports-for

It appears you can do much with multiple ports on a NIC, sweet.

 

[bill001g]

Glad you are excited but almost none of that does any good unless you have networking equipment that can support it that you can connect it to.
You will at least need managed switches to support many of these features.

You have massively mixed stuff together that is not related. Some of it is using layer 3 methods to use both ports and other is using layer 2.

For a home user this is the most unlikely way 2 ports would be used since you seldom see machines that can even come close to using 1g of bandwidth. It would be much more common that there was a specialized network that they did not want on the internet like a security camera network. So you connect 1 cable to the internet and 1 cable to the security network.

A lot of the information you will find on port bonding is old. Now that 10g and even 40g and 100g ports have gotten a lot cheaper you see much less demand for port bonding. When you have a server that can actually use more than 1g the extra costs to use 10g interfaces in both the server and the switches tends to not be that much compared to the hassle of dealing with the issues that come up using port bonding.

 

[C T]

@ bill001g Thank you for pointing out the antiquity and obsolescence of port bonding.

I am indeed excited, I enjoy learning. To provide a better understanding as to why I asked this question (and there

maybe more) I will fill in that I am indeed a student. I am 4.5 months into my A+ cert course (apprx 6 month course)

but to reiterate what had said in an above post, this hasn't a thing to do with "homework".

Though I do not have servers to manage nor networks with a 10G throughput, I may be managing some one day. I

have not yet picked my preferred tech niche, all its parts are which I've had contact with are thoroughly interesting to

me. I plan to take Network+ shortly after I am done with the current course, there shall be no rest for the wicked and I have been quite so.


Speaking of learning I have to learn the formatting of this forum.







If one has a query, it is best to start digging as others are most certainly weighted by the shovel.

 

[popatim]

So basically you have found out everything.
Sorry to have put you off at first but we get alot of request for help with homework and in those case we try to guide rather than answer directly.

Two nicks allows for 2 independant networks, bridging two different networks, binding, balancing, broadcasting, failover, IP based hardware like a printer that you mentioned

Hmmm. Did I miss anything? LoL

 

[Kewlx25]

Newer Layer2 protocols allow for bonding and failover at the same time, even over multiple paths.