What allows vpn to work?

Hello all. I know my question seems like it could have many answers. I'll
narrow it down. I am a tech at my compnay trying to make some sense of VPN.
It seems that when I, at home, access my compnay network through my
broadband\cable modem I get in without any problems. I don't have any special
configurations at home and no firewall setup. Everybody at my company who go
through broadband at home get in with no problem. Here's my question....why
is it that when people are traveling and they use an ethernet high-speed
internet connection from either a hotel or an airport do they have trouble
vpn'ing into the network? The error message is either Error 619 "The
specified port is not connected"....or error message 721:verifying username
and password' phase stalls and the message is "the remote computer did not
respond". Also, sometimes, when somoene does actually connect from a
"high-speed" internet connection at a hotel or airport they sometimes are
prompted for a username/password/domain when trying to access a network
resource such as Outlook. I guess what I want to know is this:

1. Are there any ports that need to be open for vpn to work that should be
open at the hotel and if so what can I use to check to see if the port is
open?(maybe telenet)
2. Are there any other security restrictions (firewall maybe)that a
hotel/airport could implement that I should know about that could prevent vpn
from working?
3. Are there any other restrictions that a hotel/airport could implement
that I should know about that could cause me to be prompted for
username\password\domain when trying to access Outlook?
4. Are there any questions I could ask the hotel that would answer my
questions right away?
5. Are there any known issues with using VPN from home through a wireless
setup? I ask this because people complain that their connection to the
Exchange server sometimes drops when vpn'ed over wireless.

Really folks...other than knowing that VPN will not work from behind a
firewall I don't know much about vpn. Thanks in advance!

too many questions to answer. for the curity reasons, by deault, some routers or firewall need to configure for incoming and outgoing, the good example is Cisco firewall PIX. even you establish the vPN conenction, you may not be able to browse or access the network resources because the name resolution. this browsing ovr VPN may help, http://howtonetworking.com/VPN/browsingovervpn0.htm

Don't send e-mail or reply to me except you need consulting services. Posting on MS newsgroup will benefit all readers and you may get more help.

Bob Lin, MS-MVP, MCSE & CNE
How to Setup Windows, Network, Remote Access on http://www.HowToNetworking.com
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
This posting is provided "AS IS" with no warranties.
I recommend Brinkster for web hosting!

"pd" <(E-Mail Removed)> wrote in message news846517B-A044-448A-85D8-(E-Mail Removed)...
Hello all. I know my question seems like it could have many answers. I'll
narrow it down. I am a tech at my compnay trying to make some sense of VPN.
It seems that when I, at home, access my compnay network through my
broadband\cable modem I get in without any problems. I don't have any special
configurations at home and no firewall setup. Everybody at my company who go
through broadband at home get in with no problem. Here's my question....why
is it that when people are traveling and they use an ethernet high-speed
internet connection from either a hotel or an airport do they have trouble
vpn'ing into the network? The error message is either Error 619 "The
specified port is not connected"....or error message 721:verifying username
and password' phase stalls and the message is "the remote computer did not
respond". Also, sometimes, when somoene does actually connect from a
"high-speed" internet connection at a hotel or airport they sometimes are
prompted for a username/password/domain when trying to access a network
resource such as Outlook. I guess what I want to know is this:

1. Are there any ports that need to be open for vpn to work that should be
open at the hotel and if so what can I use to check to see if the port is
open?(maybe telenet)
2. Are there any other security restrictions (firewall maybe)that a
hotel/airport could implement that I should know about that could prevent vpn
from working?
3. Are there any other restrictions that a hotel/airport could implement
that I should know about that could cause me to be prompted for
username\password\domain when trying to access Outlook?
4. Are there any questions I could ask the hotel that would answer my
questions right away?
5. Are there any known issues with using VPN from home through a wireless
setup? I ask this because people complain that their connection to the
Exchange server sometimes drops when vpn'ed over wireless.

Really folks...other than knowing that VPN will not work from behind a
firewall I don't know much about vpn. Thanks in advance!

VPN using PPTP requires two things. It requires tcp port 1723 (which is
pptp) and it requires GRE (Generic Routing Encapsulation) which is IP
protocol 47.

The pptp protocol looks after setting up and maintaining the tunnel. GRE
is concerned with the tunnelled data.

If port 1723 is blocked, you will get error 619. Without pptp, the
tunnel cannot be set up.

Error 721 indicates that GRE is being blocked. The encrypted VPN data is
carried inside a packet with a GRE header. If anything in the path blocks
GRE, no data is transferred, so the tunnel closes.

"pd" <(E-Mail Removed)> wrote in message
news846517B-A044-448A-85D8-(E-Mail Removed)...
> Hello all. I know my question seems like it could have many answers. I'll
> narrow it down. I am a tech at my compnay trying to make some sense of
> VPN.
> It seems that when I, at home, access my compnay network through my
> broadband\cable modem I get in without any problems. I don't have any
> special
> configurations at home and no firewall setup. Everybody at my company who
> go
> through broadband at home get in with no problem. Here's my
> question....why
> is it that when people are traveling and they use an ethernet high-speed
> internet connection from either a hotel or an airport do they have trouble
> vpn'ing into the network? The error message is either Error 619 "The
> specified port is not connected"....or error message 721:verifying
> username
> and password' phase stalls and the message is "the remote computer did not
> respond". Also, sometimes, when somoene does actually connect from a
> "high-speed" internet connection at a hotel or airport they sometimes are
> prompted for a username/password/domain when trying to access a network
> resource such as Outlook. I guess what I want to know is this:
>
> 1. Are there any ports that need to be open for vpn to work that should be
> open at the hotel and if so what can I use to check to see if the port is
> open?(maybe telenet)
> 2. Are there any other security restrictions (firewall maybe)that a
> hotel/airport could implement that I should know about that could prevent
> vpn
> from working?
> 3. Are there any other restrictions that a hotel/airport could implement
> that I should know about that could cause me to be prompted for
> username\password\domain when trying to access Outlook?
> 4. Are there any questions I could ask the hotel that would answer my
> questions right away?
> 5. Are there any known issues with using VPN from home through a wireless
> setup? I ask this because people complain that their connection to the
> Exchange server sometimes drops when vpn'ed over wireless.
>
> Really folks...other than knowing that VPN will not work from behind a
> firewall I don't know much about vpn. Thanks in advance!
>

You are not alone, your description pretty much describes our experiences as
well. I suspect a lot of these public networks may be firewalled or NAT'd
without consideration for the protocols required to establish VPN. Most of
our remote users are just looking for Exchange Server connections, so we'll
be doing some trials of the new Outlook over SSL functionality in place of
regular Outlook connections over a VPN. Since SSL is a TCP protocol whereas
PPTP and L2TP require other protocols, I'm thinking this will be more
compatible with these various public networks...


"pd" <(E-Mail Removed)> wrote in message
news846517B-A044-448A-85D8-(E-Mail Removed)...
> Hello all. I know my question seems like it could have many answers. I'll
> narrow it down. I am a tech at my compnay trying to make some sense of
> VPN.
> It seems that when I, at home, access my compnay network through my
> broadband\cable modem I get in without any problems. I don't have any
> special
> configurations at home and no firewall setup. Everybody at my company who
> go
> through broadband at home get in with no problem. Here's my
> question....why
> is it that when people are traveling and they use an ethernet high-speed
> internet connection from either a hotel or an airport do they have trouble
> vpn'ing into the network? The error message is either Error 619 "The
> specified port is not connected"....or error message 721:verifying
> username
> and password' phase stalls and the message is "the remote computer did not
> respond". Also, sometimes, when somoene does actually connect from a
> "high-speed" internet connection at a hotel or airport they sometimes are
> prompted for a username/password/domain when trying to access a network
> resource such as Outlook. I guess what I want to know is this:
>
> 1. Are there any ports that need to be open for vpn to work that should be
> open at the hotel and if so what can I use to check to see if the port is
> open?(maybe telenet)
> 2. Are there any other security restrictions (firewall maybe)that a
> hotel/airport could implement that I should know about that could prevent
> vpn
> from working?
> 3. Are there any other restrictions that a hotel/airport could implement
> that I should know about that could cause me to be prompted for
> username\password\domain when trying to access Outlook?
> 4. Are there any questions I could ask the hotel that would answer my
> questions right away?
> 5. Are there any known issues with using VPN from home through a wireless
> setup? I ask this because people complain that their connection to the
> Exchange server sometimes drops when vpn'ed over wireless.
>
> Really folks...other than knowing that VPN will not work from behind a
> firewall I don't know much about vpn. Thanks in advance!
>