ICND1 questions

Hi all,

i have a few questions i just don't get..They are probably simple for you, but somehow after all this studying i can't think straight anymore.

I have a few questions i dont know the answer to:

1) a host wants to go the internet. When he tries to load a website from what server will it request the info first...the gateway or the dns?

2) when a host has a static ip address and no dns servers are specified, but a default gateway is specified and the host cannot get to the internet, all the other hosts don't have a problem. What could be the reason of this?

3) is it possible that a host and the default gateway are in the same subnet, and that in the network there's a dhcp server with a totally different ip address giving addresses to dhcp clients? let's say 192.168.1.100 for the client, 192.168.1.1 for the gateway. And a dhcp server with a 10.10.10.1 on totally different range and subnet???

4) you have a question on the exam, where you can login to one switch...and you have to enter the correct interfaces for all the other switches. you can use the show cdp neighbors command to look at the connections. Are the port id's the local interfaces of the remote attached switches? so when you fill in the differente interfaces in the exam for the remote switches, you use the port ids you find in the show cdp neighbors?

5) is there a layer 1,2 explanation of the different light status of the switches, blinking green, constant green, amber etc??

my apologies for my english and the weird, and probably stupid questions.

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Comments

hypnotoad

Dalma wrote: »

Hi all,

1) a host wants to go the internet. When he tries to load a website from what server will it request the info first...the gateway or the dns?

The first thing the it will do if you're trying to access a site with a name is hit the DNS server. It has to know the IP address before it can go find it. That's what DNS is for. So to answer your question, it willl go to DNS first if you use a name. If it already knows the name (most devices have a cache of recently used records, or a HOSTS file), it will skip that step. After it has resolved the server's IP from the name (one way or another), it will try to contact the server. If the server is on the local subnet, it will go to it directly. Otherwise, it will go to the gateway. Basically, the internet only knows about IP's -- DNS is for humans. It has to get the IP somehow to know how to communicate.

Dalma wrote: »

3) is it possible that a host and the default gateway are in the same subnet, and that in the network there's a dhcp server with a totally different ip address giving addresses to dhcp clients? let's say 192.168.1.100 for the client, 192.168.1.1 for the gateway. And a dhcp server with a 10.10.10.1 on totally different range and subnet???

It's possible but not common. DHCP requests are broadcasts that will go to everything in the subnet. Usually the DHCP server is in the same subnet, but you can tell a device (such as the gateway) to forward requests to a machine on a different subnet.

Dalma wrote: »

4) you have a question on the exam, where you can login to one switch...and you have to enter the correct interfaces for all the other switches. you can use the show cdp neighbors command to look at the connections. Are the port id's the local interfaces of the remote attached switches? so when you fill in the differente interfaces in the exam for the remote switches, you use the port ids you find in the show cdp neighbors?

show cdp neighbors will work on the exam just as you'd expect on the real routers. it's a good command to know. cisco tries to make the sims as real as possible.

Dalma wrote: »

5) is there a layer 1,2 explanation of the different light status of the switches, blinking green, constant green, amber etc??

In the real world, it varies by vendor. In Cisco, blinking green is a good sign -- it means traffic is moving. Amber means a port is in an errored (or less than desirable state -- such as 10 megabit) state. Most switches also have a button on the front that will tell you PoE status, speed, etc by pressing the button.

Dalma wrote: »

my apologies for my english and the weird, and probably stupid questions.

Don't worry. Good questions. Your english is fine. Welcome to the forums and feel free to ask anything about ICND1 -- a lot of people here have taken it.

Dalma

hypnotoad wrote: »

The first thing the it will do if you're trying to access a site with a name is hit the DNS server. It has to know the IP address before it can go find it. That's what DNS is for. So to answer your question, it willl go to DNS first if you use a name. If it already knows the name (most devices have a cache of recently used records, or a HOSTS file), it will skip that step. After it has resolved the server's IP from the name (one way or another), it will try to contact the server. If the server is on the local subnet, it will go to it directly. Otherwise, it will go to the gateway. Basically, the internet only knows about IP's -- DNS is for humans. It has to get the IP somehow to know how to communicate.

Ok that's clear, but let's say the dns server is not in the same subnet. It has to go through the gateway first in order to reach that other subnet, or doesn't this make sense.

It's possible but not common. DHCP requests are broadcasts that will go to everything in the subnet. Usually the DHCP server is in the same subnet, but you can tell a device (such as the gateway) to forward requests to a machine on a different subnet.

show cdp neighbors will work on the exam just as you'd expect on the real routers. it's a good command to know. cisco tries to make the sims as real as possible.

What i mean is, when you use show cdp neighbors, it gives you the local interfaces and port ids. Look at this example:

SW-AC3#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID
SW-DS1 Fast 0/9 170 S 2621 Fast 0/1
SW-AC2 Fast 0/12 130 S 2621 Fast 0/3
SW-AC3#

So SW-AC3 has 2 local fe ports, 0/9 and 0/12 and 2 other devices are attached to this ports. SW-DS1 is attached with its local port fast 0/1. Is it correct to say the port ids you see in this example are the local interfaces of the remote switches to which the SW-AC3 is attached to?

In the real world, it varies by vendor. In Cisco, blinking green is a good sign -- it means traffic is moving. Amber means a port is in an errored (or less than desirable state -- such as 10 megabit) state. Most switches also have a button on the front that will tell you PoE status, speed, etc by pressing the button.

ok, is the recap correct:

blinking green: layer 2 connection
amber: layer 1 problem

what is constant green?

and will this be asked at the exam?

Don't worry. Good questions. Your english is fine. Welcome to the forums and feel free to ask anything about ICND1 -- a lot of people here have taken it.

Thanks for the explanations so far, but i still have some additional questions.

See inline in red!

Neeko

Ok that's clear, but let's say the dns server is not in the same subnet. It has to go through the gateway first in order to reach that other subnet, or doesn't this make sense.

Correct. Any IP address outside of the local subnet will be sent to the default gateway - that is the point of having one. So...

1. You enter google.com
2. The host wants to ask the DNS server where google.com is
3. The host detects the DNS server's IP address is on a different subnet, so forwards it to the default gateway
4. The default gateway forwards the message onto another subnet or the Internet

So SW-AC3 has 2 local fe ports, 0/9 and 0/12 and 2 other devices are attached to this ports. SW-DS1 is attached with its local port fast 0/1. Is it correct to say the port ids you see in this example are the local interfaces of the remote switches to which the SW-AC3 is attached to?

Correct.

ok, is the recap correct:

blinking green: layer 2 connection
amber: layer 1 problem

what is constant green?

and will this be asked at the exam?

SYST
Off - switch is off
Green - switch is on and IOS is loaded
Amber - POST failed

For the port LEDs, it depends what you have the 'mode' button set to. The mode button indicates what each port LED means.

STAT
Off - link is not working
Green - link is working but there is no traffic
Flashing green - link is working and traffic is passing
flashing amber - link is administratively down or dynamically disabled

SPEED
Off - 10Mbps
Green - 100Mbps
Flashing green - 1Gbps

DUPLEX
Off - half
Green - full

Dalma

thnx for the answers

last question.

Let's look at the following example.

I have to configure the serial interface and the fe interface of a router.

I get the following network address. 192.168.169.0/28

The question is, to configure the serial interface with the 12th subnet (last ip address in the range) and the fe interface with the 5th subnet.

Ip subnet zero cannot be used in this example.

How to proceed??

motherwolf

A /28 is a 255.255.255.240 mask which is going to make your subnets increments of 16. With a no ip subnet zero in effect you are not allowed to use the first or last subnets. So, you can't use .0-.16 or .240-.256. This means that your 12th subnet is .192-.208 and the last host address available on that subnet is .206 (.207 is broadcast). Your 5th subnet is going to be .80-.96 with a host range of .81-.94.(not sure if you were looking for the last available host or not).

HTH

Dalma

Hi Motherwolf,

i am too tired to practice your answer.

I had my exam this morning and I passed with 925. Don't ask how, i just don't get it..I thought i failed. Alot of questions were not clear to me.

But on the other hand, the scenario questions where you have to login to the router and switch went well.

I'm looking into your answer tomorrow, and will practice a little. I can't stand it when i don't understand something

thanks guys for all the answers. it helped me alot during the exam.

Dalma

thnx i understand the subnetquestion now.

davidspirovalentine

Dalma, GREAT attitude!!! I love the way that you still go back to something even though you passed. Most people don't have that attitude, keep it up and Congrats!!!

Im studying for ICND1 aswell. It is killing me!!! How long did you study for and how much experience do you have?