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V.T. Eric Layton
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V.T. Eric Layton

The Question of the Day

 

When a host A attempts to send data to another machine, and determines that the destination machine is not in its own subnetwork, where must host A send the data first by default?

 

A. To its nearest neighbor device

B. To the loop address 127.0.0.1

C. To its default router

D. To the destination machine's controlling hub

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C

The Question of the Day

 

When a host A attempts to send data to another machine, and determines that the destination machine is not in its own subnetwork, where must host A send the data first by default?

 

A. To its nearest neighbor device

B. To the loop address 127.0.0.1

C. To its default router

D. To the destination machine's controlling hub

C , and if it isn't , man would I like to hear that explanation.
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V.T. Eric Layton

C is the correct answer. All hosts on a single broadcast domain (a router port by definition) must know their default gateway IP address in order to communicate with devices outside of the local subnet (broadcast domain). For a host newly installed, the first step toward sending data is to send an arp broadcast request out looking for the default gateway. Once the default gateway address is obtained, the host can begin sending data outside of its own subnet.

 

Very good. Everyone got that one correct. :)

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V.T. Eric Layton

The Question of the Day

 

Before the advent of networking devices that could internally compensate for incorrect cabling, the proper cabling was a critical part of getting a network up and running. With this in mind, assuming older equipment is in use here (see Fig 1), what type of cabling would be used between the PCs and the switches in this drawing?

 

Untitled.png

 

A. a rollover cable

B. a straight-through cable

C. a fiber-optic cable

D. a cross-over cable

 

*Bonus points for anyone who can tell us what the primary use of a rollover cable might be.

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cross-dressing cable.

 

most equipement these daze (switches, et al) have ports with pairs that can tx or rx

in the old days, a newbie network guy could fry hub/switch ports by plugging a cross over cable into it when a regular cable was required.

really amuzing. unless you consider the cost of the ruined equip... :o

 

sorry for dropping in, but i have to amuse myself somehow...

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Guest LilBambi

A. Rollover cable?

 

or is it:

 

D. Crossover cable?

 

Or is it both?

 

Seems that you would use crossover for the local networks and maybe a rollover cable for the between location....

 

Rollover cable (also known as Cisco console cable or a Yost cable) is a type of null-modem cable that is often used to connect a computer terminal to a router's console port.

 

Sounds like a dry pair to me...

Edited by LilBambi
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lets see, i was doing networking setups in the 80's and never used anything but straight-through when connecting pc's to the outside world interface,

so I am going to go with If you have such a situation , make them update the equipment and not even fuss with this

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Guest LilBambi

We used BNC in the 80s, which would be coax, and they had to be terminated properly, but they also had in companies, token ring style right in that time frame? Was that the straight through kind crp or were you using BNC coax in the 80s too?

 

I was trying to go with still using some form of ethernet and routers...but could be even earlier and straight through would be more likely as crp said...

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V.T. Eric Layton

OK...

 

The rule was that because of the TX and RX pinouts on similar and dissimilar devices, either straight-through or cross-over cables are required.

 

Similar devices all transmit and receive on the same pins, so in order to properly connect these devices together, the TX and RX lines would have to "cross over"; meaning that a crossover cable would be required. Pin 1 to Pin 3 and Pin 2 to Pin 6.

 

Dissimilar devices all transmit and receive on different pins, so in order to properly connect these devices together, the TX and RX lines would have to go "straight thought"; meaning that a straight-through cable would be necessary. Pin 1 to Pin 1 and Pin 2 to Pin 2, etc.

 

Routers, PCs, and APs (access points) are all similar devices.

 

Hubs, bridges, and switches are all similar devices.

 

When connecting a PC to a switch, since they are dissimilar devices, they would need a straight-though cable.

 

*Note: As mentioned in the question, most networking devices nowadays use internal logic to correct pinouts when incorrect cables are used.

 

Interesting website explanation: http://learn-network...rollover-cables

=====

 

Extra bonus points to Fran for finding the bit about rollover cables. :)

 

Rollover cable (all 8 wires rolled over from one connector to the other - 1 to 8, 2 to 7, 3 to 6, etc.) is used to access a router or switch using a PC's serial port on one end and the Console connection on the router or switch. This configuration is used to manipulate/configure the device. After initial configuration, password set-up, and telnet/ssh enabling has occurred, the network devices can be accessed remotely.

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V.T. Eric Layton

Question of the Day

 

Ok, here's an easy one...

 

How many assignable host IP address are available using the Network 192.168.1.0/24?

 

A. 254

B. 512

C. 256

D. 1024

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Question of the Day

 

Ok, here's an easy one...

 

How many assignable host IP address are available using the Network 192.168.1.0/24?

 

A. 254

B. 512

C. 256

D. 1024

a

:o they actually ask a question that is somewhat practical ?

Edited by crp
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Guest LilBambi

A. 254

 

If I remember correctly...

 

/24 is the subnet mask aka 192.168.1.0 255.255.255.0 aka class c subnet

 

Addressable range from 192.168.1.1 to 192.168.1.254 (192.168.1.0 and 192.168.1.255 reserved for network ID/base and broadcast)

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V.T. Eric Layton

You people are pretty sharp. :)

 

A. 254 is the proper answer because...

 

/24 is the subnet mask aka 192.168.1.0 255.255.255.0 aka class c subnet

 

Addressable range from 192.168.1.1 to 192.168.1.254 (192.168.1.0 and 192.168.1.255 reserved for network ID/base and broadcast

 

Great explanation, so I just Copy/Pasted that one. ;)

 

OK, well... tomorrow's the big day, so we'll hold off on the next Question of the Day till another time... unless one of you wants to contribute a question.

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Guest LilBambi

Yea! May all your questions have proper answers tomorrow! Or at least most of them!

 

Relax and let your brain mellow tonight...don't want to go in for a test anxious. :D

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V.T. Eric Layton

Oh, I'm sure all the questions have proper answers. The trick is choosing the right ones. ;)

 

EDIT: I just had a BLAST of déjà vu when I posted the above comment a second or so ago. I hope that's a good omen. :yes:

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here's today's q:

router flap

 

what is it? does it matter to a home user?

 

ps

added "...to a home user"

Edited by Temmu
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here's today's q:

router flap

what is it? does it matter to a home user?

:hmm: i think this is the thing that used to be called something else ("jitter"?) , is this the router taking different routes to an external ip address depending on the internal ip requesting? so a home user might have cause to care.
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Guest LilBambi

I have heard of router flapping, but router flap...not really.

 

However, there is such an animal! Amazing!

 

Google Books reference from Intrusion Detection with Snort by Jack Koziol:

 

Router Flap

 

When routes on the Internet suddenly appear and disappear, frequently packets may be forwarded through drastically different routes on the Internet. When packets are forwarded through different routers on the Internet, they can possibly have widely varying TTL values. Some packets may find a direct route and have a large TTL, whereas others may have to traverse many differnet hops to reach the same destination....

 

More on it in the book.

 

crp is right. I think most of us are familiar with the phenomenon for many years, but didn't know it was called router flap. At least I didn't know that it was called that.

 

 

:thumbsup:

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V.T. Eric Layton

I thought router flap was when to adjacent routers have an argument. No, wait... maybe that's a router row I'm thinking. ;)

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V.T. Eric Layton

I don't think so.... Verizon's FIOS router is the worst. :(

 

Adam

 

Hmm... I haven't had any issues with my Westell 9100EM (Verizon provided) multi-purpose device. It's not just a router, you know... it's a switch/router/access point/DHCP server-client/firewall/NAT-PAT IP translator. :)

 

I can say carp like the above with authority now that I'm Cisco certified. :lol:

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