Newbie needs help understanding DNS

[GoBruins]

hi,

i'm trying to grasp the concept of DNS. here's what i understand so
far:

there are a bunch of DNS Server computers out there on the internet
that act to resolve names to IP addresses. for example if i punch in
yahoo.com, i (being the client) send out a request to these Servers,
asking them to resolve 'yahoo.com' to an IP address like
'64.25.152.12'. if the first DNS server doesn't have the answer in
their system (or has it cached), it passes along the request to another
DNS server and so on, until the right DNS server that controls the
resolutions for that 'zone' is found. so far so good?

okay, so i'm on the internet via an SBC DSL connection, and using a
Linksys wireless router. the router status page tells me that i'm
connected via PPPoE, and that i've been given a certain IP address. it
aso shows this:

DNS 1: 68.94.156.1
DNS 2: 68.94.157.1

i'm assuming that these are SBC's default DNS servers? and the second
one is in case the first is overloaded. am i correct?

going further: my router's IP address is

192.168.1.1

i then played with my local PC's TCP/IP properties. instead of having
the router's DHCP service assign an IP address to my PC, i punched in
my own:

192.168.1.3

with a subnet mask of:

255.255.255.0

under Default gateway, i punched in the router's IP address. again:

192.168.1.1

so far, so good. under 'Use the following DNS server addresses', i
punched in random IP addresses. it didn't work (as expected), and i
couldn't surf the net.

if i punched in the IP addresses from the router status page (mentioned
above)

DNS 1: 68.94.156.1
DNS 2: 68.94.157.1

i could surf, no problem. now here's the part i don't understand. if i
punch in my router's IP address of 192.168.1.1, it also works! i can
surf, etc.

how is this possible? what does my router have to do with any kind of
DNS services?

thanks in advance.

 

[Kurt]

hi,

i'm trying to grasp the concept of DNS. here's what i understand so
far:

there are a bunch of DNS Server computers out there on the internet
that act to resolve names to IP addresses. for example if i punch in
yahoo.com, i (being the client) send out a request to these Servers,
asking them to resolve 'yahoo.com' to an IP address like
'64.25.152.12'. if the first DNS server doesn't have the answer in
their system (or has it cached), it passes along the request to another
DNS server and so on, until the right DNS server that controls the
resolutions for that 'zone' is found. so far so good?

Yes, in a structured sort of way.

okay, so i'm on the internet via an SBC DSL connection, and using a
Linksys wireless router. the router status page tells me that i'm
connected via PPPoE, and that i've been given a certain IP address. it
aso shows this:

DNS 1: 68.94.156.1
DNS 2: 68.94.157.1

i'm assuming that these are SBC's default DNS servers? and the second
one is in case the first is overloaded. am i correct?

Close. Overloading could be a scenario that would cause your computer to use
the "alternate" DNS server. But the true test is whether or not the
"preferred" DNS server responds within a specific timeframe, for whatever
reason. It could be down for maintenence, crashed, overloaded, etc..

going further: my router's IP address is

192.168.1.1

i then played with my local PC's TCP/IP properties. instead of having
the router's DHCP service assign an IP address to my PC, i punched in
my own:

192.168.1.3

with a subnet mask of:

255.255.255.0

under Default gateway, i punched in the router's IP address. again:

192.168.1.1

so far, so good. under 'Use the following DNS server addresses', i
punched in random IP addresses. it didn't work (as expected), and i
couldn't surf the net.

if i punched in the IP addresses from the router status page (mentioned
above)

DNS 1: 68.94.156.1
DNS 2: 68.94.157.1

i could surf, no problem. now here's the part i don't understand. if i
punch in my router's IP address of 192.168.1.1, it also works! i can
surf, etc.

how is this possible? what does my router have to do with any kind of
DNS services?

Many, in fact probably most SOHO-type routers these days function as a DNS
proxy. If you set everything back to "acquire automatically" in your TCP/IP
properties page, then type "ipconfig /all" from the command line, I'll bet
your DNS server is listed as 192.168.1.1. There are a lot of reasons for
doing this, but a real common one is if the router performs some sort of
content filtering. If a site doesn't meet the content requirements, the
router will substitute the IP address (or more properly, a redirect) of a
locally generated page informing you that this site is not allowed.


....kurt

 

[GoBruins]

good stuff, Kurt. thanks very much.

Yes, in a structured sort of way.


Close. Overloading could be a scenario that would cause your computer to use
the "alternate" DNS server. But the true test is whether or not the
"preferred" DNS server responds within a specific timeframe, for whatever
reason. It could be down for maintenence, crashed, overloaded, etc..



Many, in fact probably most SOHO-type routers these days function as a DNS
proxy. If you set everything back to "acquire automatically" in your TCP/IP
properties page, then type "ipconfig /all" from the command line, I'll bet
your DNS server is listed as 192.168.1.1. There are a lot of reasons for
doing this, but a real common one is if the router performs some sort of
content filtering. If a site doesn't meet the content requirements, the
router will substitute the IP address (or more properly, a redirect) of a
locally generated page informing you that this site is not allowed.


...kurt