Networking Question

bigaudiofanatic · June 2010

Me and some friends from class are studying networking. We are stuck on something. Does DNS come before or after DHCP and how do the interact with each other?

Amherst · June 2010

Obtaining an address thru DHCP comes first. DHCP will then point to the DNS box.

bigaudiofanatic · June 2010

Thank you

Amherst · June 2010

Keep in mind they are really separate entities. Once an address is established on a particular subnet, for data transmission on that subnet, dns enables name resolution to communicate with a particular IP. Whether it be an inside or outside IP.

bigaudiofanatic · June 2010

Amherst wrote: »

Keep in mind they are really separate entities. Once an address is established on a particular subnet, for data transmission on that subnet, dns enables name resolution to communicate with a particular IP. Whether it be an inside or outside IP.

We are not there yet but thank you, wil keep that in mind.

PhantomOG · June 2010

Speaking of networking, everyone be sure to back up your router settings if you can. Yesterday we had thunderstorms and brief blackouts that somehow managed to hose my wireless router settings (DD-WRT). So I had to spend a couple hours last night re-setting everything up (mac filter lists, static IP's, etc). What a pain in the... at least now I have my router settings backed up and saved to several places in case it ever happens again.

Amherst · June 2010

Glad to help.

Are you studying through Cisco's world or Big Blue's?

bigaudiofanatic · June 2010

Cisco Academy

WilliamM2 · June 2010

PhantomOG wrote: »

Speaking of networking, everyone be sure to back up your router settings if you can. Yesterday we had thunderstorms and brief blackouts that somehow managed to hose my wireless router settings (DD-WRT). So I had to spend a couple hours last night re-setting everything up (mac filter lists, static IP's, etc). What a pain in the... at least now I have my router settings backed up and saved to several places in case it ever happens again.

I had something even worse happen. Apparently my wireless router re-set itself to defaults, I have no idea when this happened, but apparenty I have been running an unsecured wireless connection. Good way for the nieghbors to get free internet!

KrazyMofo24 · June 2010

DHCP will provide the DNS server's address along with the ip address, and gateway. Once the PC tries to open a webpage via a URL(www.polkaudio.com) the router will get the IP address from the DNS server, and the PC will store the DNS entry in it's local table.

Amherst · June 2010

You're close...some of your details are missing and incorrect.

First the router is not involved at all, it simply handles the ip as any other communication. The PC communicates directly with the DNS server. The DNS server communicates directly to outside DNS servers for outside addresses. Inside addresses are handled by an inside DNS server, usually, but not necessarily the same server.
DNS then reports back to PC with requested address if known.

Big Audio good luck with your training, just finished up mine and now preparing for cert.

quadzilla · June 2010

Amherst wins the prize, but what no one mentioned is that DHCP will only hand out the parameters it's been told to. DHCP doesn't have to give out DNS, or even a gateway. It can be configured to hand out just an IP and nothing else. Most clients can also over ride things like DNS settings. For some real fun, either read the man page for dhcpd or look at all the settings available in the MS DHCP server.

Amherst · June 2010

Thanks, used an extremely simplified version of the process. Didn't want to mention missing settings. The big lesson is how important the DNS process is to the whole big picture.

Lets not get into throwing 98 and NT boxes into the mix. Now that's fun!

bruss · June 2010

Amherst wrote: »

You're close...some of your details are missing and incorrect.

First the router is not involved at all, it simply handles the ip as any other communication. The PC communicates directly with the DNS server. The DNS server communicates directly to outside DNS servers for outside addresses. Inside addresses are handled by an inside DNS server, usually, but not necessarily the same server.
DNS then reports back to PC with requested address if known.

Big Audio good luck with your training, just finished up mine and now preparing for cert.

my router is totally involved as thats where my DHCP is handled and DNS is assingned. After that it is as you state, just a packet routed to that DNS ip address.

ip dhcp pool 0
network 10.10.10.0 255.255.255.0
domain-name xxxxxxx.homeunix.net
default-router 10.10.10.1
dns-server xx.****.201.148

Amherst · June 2010

Don't mistake that setting in the router as being part of the DNS process or service. Requests are handled as stated.

The router when set to handle DHCP will by necessity (most cases) need to point to DNS.

KrazyMofo24 · June 2010

Amherst wrote: »

You're close...some of your details are missing and incorrect.

First the router is not involved at all, it simply handles the ip as any other communication. The PC communicates directly with the DNS server. The DNS server communicates directly to outside DNS servers for outside addresses. Inside addresses are handled by an inside DNS server, usually, but not necessarily the same server.
DNS then reports back to PC with requested address if known.

Big Audio good luck with your training, just finished up mine and now preparing for cert.

You're right I mean that the router will forward the packets...I should have phrased it better. The PC itself does store dns entries so it doesn't always have to query the DNS server if it's already been there once.

Most home networks will go to the ISP's DNS server which is tiered, and of course the inside ones for the rest.

Bruss that's showing the settings for DHCP and what addresses (IP, Gateway, DNS) to provide to the client.

Amherst · June 2010

KrazyMofo24 wrote: »

The PC itself does store dns entries so it doesn't always have to query the DNS server if it's already been there once.

^^^Necessary to keep from soaking the bandwidth.^^^

Is the OP listening...getting his study on? HeHe.

bruss · June 2010

Amherst wrote: »

Don't mistake that setting in the router as being part of the DNS process or service. Requests are handled as stated.

The router when set to handle DHCP will by necessity (most cases) need to point to DNS.

Yeah it is absolutley not doing any DNS lookups just assinging the dns I wish to use.

KrazyMofo24 wrote: »

Bruss that's showing the settings for DHCP and what addresses (IP, Gateway, DNS) to provide to the client.

Yea. just what i want to hand out for pool0. I have a different pool with a different subnet for my wireless clients.

potee · July 2010

Ok guys I use an ethernet cable to my desk top and go wirelessly to the laptop and the PS 3. Ibought a DAP-1522 to use as a bridge to my Viera V10 tv. I've tried to make it work without any luck. It says network is ok but Viera Cast wants a DNS. I tried the one thats on the router page no luck. I'm away from home right now but will be home in 8-10 days. Hopefully you will tell me things to try by then. Thanks for any suggestions.

Paul

bigaudiofanatic · July 2010

Can anyone explain this to us and how we are suppose to be reading it? We have been looking at it for two days and not sure which way to look at it and how it is being explained.

Amherst · July 2010

Header chart.
The blocks show the amount of bits used for each section (termed field) of the header.

Source=16bits
Destination=16bits
Sequence=32bits
ect.

bigaudiofanatic · July 2010

WOW....thanks we all stupid.

Amherst · July 2010

Never stupid.

Hey BAF, I'll have to dig up some of my goodies for study if you like and send a copy your way. Some good stuff that helps with sorting out the Cisco way.

Do you have a copy of Wire Shark to watch this stuff in action?

bigaudiofanatic · July 2010

Ya we are using wire shark and we have been getting into it little at a time. We appreciate any help.

KrazyMofo24 · July 2010

CBT nuggets are good too. Check out techexams.net that's a good forum.

bigaudiofanatic · July 2010

Ok we are on chapter 6 and completely lost. Considering the teacher did not explain what we asked him to we are in the dark.

One of the first questions for our lab for understanding is.

Which IP addresses are network addresses?

a.64.104.3.7/28
b.192.168.12.64/26
c.192.135.12.191/26
d.198.18.12.16/24
e.209.165.200.254/27
f.220.12.12.33/27

What makes them different how can you see what is an networking address?

concealer404 · July 2010

What kind of network? Private?

If so, answer B is within the blocks set for private network.

bigaudiofanatic · July 2010

Networking address thats what is is asking.

Zeros · July 2010

bigaudiofanatic wrote: »

Ok we are on chapter 6 and completely lost. Considering the teacher did not explain what we asked him to we are in the dark.

One of the first questions for our lab for understanding is.

Which IP addresses are network addresses?

a.64.104.3.7/28
b.192.168.12.64/26
c.192.135.12.191/26
d.198.18.12.16/24
e.209.165.200.254/27
f.220.12.12.33/27

What makes them different how can you see what is an networking address?

Try this, it might help:

http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

John30_30 · July 2010

bigaudiofanatic wrote: »

Can anyone explain this to us and how we are suppose to be reading it? We have been looking at it for two days and not sure which way to look at it and how it is being explained.

That's the header of a TCP packet, as it mentions. The pertinent parts are Source & Destination Ports-obvious enough; Sequence # is which packet # it is of thousands or millions, Acknowledgment is the TCP handshake, UDP won't have that; checksum is to make sure the packet is original, data is data- the others are not so relevant. Sometimes Window size is used to set non-babygiant MTU frames.

Edit- didn't see Amherst's reply already explaining it.

bigaudiofanatic wrote: »

Ok we are on chapter 6 and completely lost. Considering the teacher did not explain what we asked him to we are in the dark.

One of the first questions for our lab for understanding is.

Which IP addresses are network addresses?

a.64.104.3.7/28
b.192.168.12.64/26
c.192.135.12.191/26
d.198.18.12.16/24
e.209.165.200.254/27
f.220.12.12.33/27

What makes them different how can you see what is an networking address?

the /28 or /26 etc. at the end is how it is subnetted. This is way more involved than a simple answer because you have to do the math to determine how big each subnet is, and therefore where each subnet begins and ends numerically. The 1st and last #'s are network and broadcast, so they are out.

You pretty much have to work them out on paper, but I can tell you there are some that show up visually as being network #'s or broadcasts rather than addresses.
And we're only talking about the 4th octet. So just visually, b has 64 as its 4th and that's usually a network #. So it's out. c has 191 and that's often a broadcast #, so it's out (usually). d is out- that one's easy because it's 24 bits, 16 subnets of 14, and 256 divided by 16 is 16- so it's a network # also.
Wait- I was wrong on d. It's good. It has 254 subnet addresses. If it was /28 it would be invalid.

Sheesh.

bruss · July 2010

John30_30 wrote: »

The 1st and last #'s are network and broadcast, so they are out.

You pretty much have to work them out on paper, but I can tell you there are some that show up visually as being network #'s or broadcasts rather than addresses.
And we're only talking about the 4th octet. So just visually, b has 64 as its 4th and that's usually a network #. So it's out. c has 191 and that's often a broadcast #, so it's out (usually). d is out- that one's easy because it's 24 bits, 16 subnets of 14, and 256 divided by 16 is 16- so it's a network # also.
Wait- I was wrong on d. It's good. It has 254 subnet addresses. If it was /28 it would be invalid.

Sheesh.

Yeah I read this as which are Networks. Not Hosts or broadcasts. Been a while since i had to subnet. let me see how wrong i can get this.

a.64.104.3.7/28 Network is 64.104.3.0/255.255.255.240
b.192.168.12.64/26 Network is 192.168.12.64/255.255.255.192
c.192.135.12.191/26 Network is 192.135.12.128/255.255.255.192
d.198.18.12.16/24 Network is 192.18.12.0/255.255.255.0
e.209.165.200.254/27 Network is 209.165.200.224/255.255.255.224
f.220.12.12.33/27 Network is 220.12.12.32/255.255.255.224

Your answer is B 192.168.12.64 is a network address not a host or broadcast.

I may be way off.. lol Im sure i will be set straight in a min

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