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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Changing ISP smoothly..



 
 
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  #1  
Old August 24th 09, 08:18 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Changing ISP smoothly..

Ok, time to bite the bullet and get rid of a load of legacy junk.

Currently I have two phone lines, one of which has broadband, and whose
number I do not want to keep.

The other does not, and I would like broadband on that with a new supplier.

I run various domains hosted on my own (internal) web server.

I manage a few sites who will reject me unless I am on my old IP
address. Until reconfigured..

I have multiple domains also hosted elsewhere mainly for e-mail: These
will eventually be rationalised.

What I have decided to do is the following, and I would like the
technically knowledgeable to see if there are any flaws.

1/. Move the phone line I want to keep to IDNET. My supplier of choice.

2/. Enable broadband on that line.

3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?

6/. wait a few days for DNS to settle down to the new addresses.

7/. using my old router still as the default, reconfigure all the remote
firewalls to accept the new address also.

8/. Temporarily switch to the new router and check accessibility on the
new IP address. At this point the new ADSL becomes the default route.

9/. Move all mail clients to send via IDNET'S SMTP relay.

10/. enable DHCP and reboot all desktops to pick up the new router as
default route.

11/. Cancel original ISP.

12/. Cancel unwanted BT line

...and then set to work on the *externally* hosted domains..:-)

  #2  
Old August 24th 09, 10:29 PM posted to uk.telecom.broadband
Gordon Henderson
external usenet poster
 
Posts: 797
Default Changing ISP smoothly..

In article ,
The Natural Philosopher wrote:
Ok, time to bite the bullet and get rid of a load of legacy junk.

Currently I have two phone lines, one of which has broadband, and whose
number I do not want to keep.

The other does not, and I would like broadband on that with a new supplier.

I run various domains hosted on my own (internal) web server.

I manage a few sites who will reject me unless I am on my old IP
address. Until reconfigured..

I have multiple domains also hosted elsewhere mainly for e-mail: These
will eventually be rationalised.

What I have decided to do is the following, and I would like the
technically knowledgeable to see if there are any flaws.

1/. Move the phone line I want to keep to IDNET. My supplier of choice.

2/. Enable broadband on that line.

3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?


Remember to add a new virtual hosts entry for the new IP address for
each site.

Also - asymetric routing - it should work... And I don't know of any
ISP at present who block it if they see it, but you never know.

I'd drop the TTL on your domains a few weeks in advance, if you have
that level of control over them.


6/. wait a few days for DNS to settle down to the new addresses.

7/. using my old router still as the default, reconfigure all the remote
firewalls to accept the new address also.


You should do this as soon as you know your new IP address. Allow both old
and new for a while. Not that I'm speaking from experience or anything,
oh no...

8/. Temporarily switch to the new router and check accessibility on the
new IP address. At this point the new ADSL becomes the default route.

9/. Move all mail clients to send via IDNET'S SMTP relay.

10/. enable DHCP and reboot all desktops to pick up the new router as
default route.


You need to reboot? Shouldn't - even with windows. (Athough it might be
easier than typing the command, or using the "repair" option)

11/. Cancel original ISP.

12/. Cancel unwanted BT line

..and then set to work on the *externally* hosted domains..:-)


Good luck!

Gordon
  #3  
Old August 24th 09, 11:31 PM posted to uk.telecom.broadband
alexd
external usenet poster
 
Posts: 1,765
Default Changing ISP smoothly..

Gordon Henderson wrote:

In article ,
The Natural Philosopher wrote:


5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?


Also - asymetric routing - it should work... And I don't know of any
ISP at present who block it if they see it, but you never know.


I reckon it won't work. NAT routers/firewalls [for one] seeing responses
coming back from an IP address they didn't request them from will ignore the
traffic, and the browser will just think your site is unresponsive.

If you do manage to get a port forward working via a router that isn't the
default route for the given server, I would be interested to know how you
did it.

--
http://ale.cx/ (AIM:troffasky) )
22:23:45 up 110 days, 14:57, 3 users, load average: 0.17, 0.31, 0.23
"If being trapped in a tropical swamp with Anthony Worral-Thompson and
Christine Hamilton is reality then I say, pass the mind-altering drugs"
-- Humphrey Lyttleton


  #4  
Old August 24th 09, 11:57 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Changing ISP smoothly..

alexd wrote:
Gordon Henderson wrote:

In article ,
The Natural Philosopher wrote:


5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?


Also - asymetric routing - it should work... And I don't know of any
ISP at present who block it if they see it, but you never know.


I reckon it won't work. NAT routers/firewalls [for one] seeing responses
coming back from an IP address they didn't request them from will ignore the
traffic, and the browser will just think your site is unresponsive.


OK, is that a fair point? MM. yes, it probably is. the responses will
come from a different IP address. I'll ponder that one.
..

If you do manage to get a port forward working via a router that isn't the
default route for the given server, I would be interested to know how you
did it.


Its should not be beyond the wit of man.. actually there is one simple
way to do it. I can add a second interface on a different subnet, to the
(Linux) server, and bind a second default route to that. Nasty, but I've
done it often enough to set up routers..

That will allow symmetrical routing via either virtual interface.

So in effect my server will have two IP addresses on two interfaces with
a separate default route for either..if IP forwarding is off on it, it
won't then magically route between the two
..

So
#ifconfig etho:1 192.168.2.100
to set up a second interface on eth0:1 and

#route add default gw 192.168.2.1 eth0:1

for example..

Actually, its a fair way to make a resilient-ish server using twin DSL
if you have split DNS 'A' records.. or use DYNDNS for 'failover' DNS..

I cant remember what selects from a pair of equivalent default routes
for outbound connections. I do remember that one an NT server that was
giving precisely 50% packet loss, it simply picked alternately :-)

I do know that once a server is bound to a given interface, it will
return packets via that interface, so the question would be as to how to
bind apache to both...aha. It listens on all unless told not to. So no
issues there.

Looks like you spotted the flaw, and there is a simple enough workaround.

I wonder what happens to desktops if you have TWO DHCP servers running.



  #5  
Old August 25th 09, 12:14 AM posted to uk.telecom.broadband
alexd
external usenet poster
 
Posts: 1,765
Default Changing ISP smoothly..

The Natural Philosopher wrote:

Looks like you spotted the flaw, and there is a simple enough workaround.


This may be of interest, if you've got a spare weekend:

http://kindlund.wordpress.com/2007/1...tiple-default-
routes-in-linux/

I wonder what happens to desktops if you have TWO DHCP servers running.


If both are giving out correct information and non-overlapping, I should
have thought users would be none the wiser.

--
http://ale.cx/ (AIM:troffasky) )
23:07:30 up 110 days, 15:40, 3 users, load average: 0.08, 0.20, 0.26
"If being trapped in a tropical swamp with Anthony Worral-Thompson and
Christine Hamilton is reality then I say, pass the mind-altering drugs"
-- Humphrey Lyttleton


  #6  
Old August 25th 09, 12:37 AM posted to uk.telecom.broadband
Dennis Ferguson
external usenet poster
 
Posts: 118
Default Changing ISP smoothly..

On 2009-08-24, The Natural Philosopher wrote:
3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?


This bit confuses me a bit.

If your server is configured with a public IP address now there should
be a step in there where you add a second public address to the same
interface. The need for this probably precludes the server from using
DHCP for any configuration at all, so you'll be manually configuring
the default route in the server too (if you aren't already) and can point
it at which ever router suits you. Note, however, that it is
current best practice for ISPs to filter out traffic from customers
with source addresses other than those assigned by that ISP, and while
many (most?) ISPs don't bother with this you'll want to make sure that
one of your ISPs is among the latter or the asymmetry in the choice of
inbound and outbound ISP won't work. Some host firewall filters will
let you redirect host-generated outbound packets based on source address,
in effect allowing you to pick a default route based on the source address
of the packet you are sending, so if your server is capable of this you
may be able to straighten out the asymmetry for inbound connections this
way.

On the other hand if your server is configured with a private IP
address only, and you are configuring your router to forward port
80 via NAT to get those packets to the server, then asymmetric routing
of the return packets for inbound connections simply won't work. In
this case the only way I know to make this work is to configure a
second private address on the server, have each of the routers forward
packets to the server using a separate private address, and then
in the server use outbound packet filtering based on source address to
get the outbound packets back to the same router as the inbound
packets arrived from.

In either case it seems like you'll need a step in there where
you configure your server with a second address.

Dennis Ferguson
  #7  
Old August 25th 09, 12:46 AM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Changing ISP smoothly..

alexd wrote:
The Natural Philosopher wrote:

Looks like you spotted the flaw, and there is a simple enough workaround.


This may be of interest, if you've got a spare weekend:

http://kindlund.wordpress.com/2007/1...tiple-default-
routes-in-linux/


Hmm. I THOUGHT that was the default behaviour without having to set up
explicit routes..

I.e. that servers will respond via the interface to which they are
bound..and from which they receive IP requests..

Ping might not..

Oh well if it doesn't work the simpler way, that will assuredly work.




I wonder what happens to desktops if you have TWO DHCP servers running.


If both are giving out correct information and non-overlapping, I should
have thought users would be none the wiser.


Hmm. I tried it at one stage and things just hung, but the software was
'experimental' to say the least.
  #8  
Old August 25th 09, 01:53 AM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Changing ISP smoothly..

Dennis Ferguson wrote:
On 2009-08-24, The Natural Philosopher wrote:
3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?


This bit confuses me a bit.

If your server is configured with a public IP address now there should
be a step in there where you add a second public address to the same
interface. The need for this probably precludes the server from using
DHCP for any configuration at all, so you'll be manually configuring
the default route in the server too (if you aren't already) and can point
it at which ever router suits you. Note, however, that it is
current best practice for ISPs to filter out traffic from customers
with source addresses other than those assigned by that ISP, and while
many (most?) ISPs don't bother with this you'll want to make sure that
one of your ISPs is among the latter or the asymmetry in the choice of
inbound and outbound ISP won't work. Some host firewall filters will
let you redirect host-generated outbound packets based on source address,
in effect allowing you to pick a default route based on the source address
of the packet you are sending, so if your server is capable of this you
may be able to straighten out the asymmetry for inbound connections this
way.

On the other hand if your server is configured with a private IP
address only, and you are configuring your router to forward port
80 via NAT to get those packets to the server, then asymmetric routing
of the return packets for inbound connections simply won't work. In
this case the only way I know to make this work is to configure a
second private address on the server, have each of the routers forward
packets to the server using a separate private address, and then
in the server use outbound packet filtering based on source address to
get the outbound packets back to the same router as the inbound
packets arrived from.

In either case it seems like you'll need a step in there where
you configure your server with a second address.

Dennis Ferguson


Yup. read on..you are not the only one to point that out..

The only issue seems to be whether or not I need to set up split routing
tables.

Still even that is not a great pain really.


  #9  
Old August 25th 09, 11:58 AM posted to uk.telecom.broadband
Mark
external usenet poster
 
Posts: 525
Default Changing ISP smoothly..

On Mon, 24 Aug 2009 19:18:28 +0100, The Natural Philosopher
wrote:

Ok, time to bite the bullet and get rid of a load of legacy junk.

Currently I have two phone lines, one of which has broadband, and whose
number I do not want to keep.

The other does not, and I would like broadband on that with a new supplier.

I run various domains hosted on my own (internal) web server.

I manage a few sites who will reject me unless I am on my old IP
address. Until reconfigured..

I have multiple domains also hosted elsewhere mainly for e-mail: These
will eventually be rationalised.

What I have decided to do is the following, and I would like the
technically knowledgeable to see if there are any flaws.

1/. Move the phone line I want to keep to IDNET. My supplier of choice.

2/. Enable broadband on that line.

3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?

6/. wait a few days for DNS to settle down to the new addresses.

7/. using my old router still as the default, reconfigure all the remote
firewalls to accept the new address also.

8/. Temporarily switch to the new router and check accessibility on the
new IP address. At this point the new ADSL becomes the default route.

9/. Move all mail clients to send via IDNET'S SMTP relay.

10/. enable DHCP and reboot all desktops to pick up the new router as
default route.

11/. Cancel original ISP.

12/. Cancel unwanted BT line

..and then set to work on the *externally* hosted domains..:-)


Remember it is possible that your second line uses a different route
to the exchange and may sync at a lower speed when it is broadband
enabled.

--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking most articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.
[Reply-to address valid until it is spammed.]

  #10  
Old August 25th 09, 01:00 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 2,728
Default Changing ISP smoothly..

Mark wrote:
On Mon, 24 Aug 2009 19:18:28 +0100, The Natural Philosopher
wrote:

Ok, time to bite the bullet and get rid of a load of legacy junk.

Currently I have two phone lines, one of which has broadband, and whose
number I do not want to keep.

The other does not, and I would like broadband on that with a new supplier.

I run various domains hosted on my own (internal) web server.

I manage a few sites who will reject me unless I am on my old IP
address. Until reconfigured..

I have multiple domains also hosted elsewhere mainly for e-mail: These
will eventually be rationalised.

What I have decided to do is the following, and I would like the
technically knowledgeable to see if there are any flaws.

1/. Move the phone line I want to keep to IDNET. My supplier of choice.

2/. Enable broadband on that line.

3/. Add a second router, with DHCP temporarily disabled so that the main
router is still there and is the natural default route.

4/. configure port 80 passthrough on the new router to point at my
(web)server.

5/. Change all my public sites to point to the new static IP address. By
my reckoning the packets will all come in eventually by the new router,
but return traffic will go out of the old one?

6/. wait a few days for DNS to settle down to the new addresses.

7/. using my old router still as the default, reconfigure all the remote
firewalls to accept the new address also.

8/. Temporarily switch to the new router and check accessibility on the
new IP address. At this point the new ADSL becomes the default route.

9/. Move all mail clients to send via IDNET'S SMTP relay.

10/. enable DHCP and reboot all desktops to pick up the new router as
default route.

11/. Cancel original ISP.

12/. Cancel unwanted BT line

..and then set to work on the *externally* hosted domains..:-)


Remember it is possible that your second line uses a different route
to the exchange and may sync at a lower speed when it is broadband
enabled.

Not a worry for me.

I am actually slightly more short of upload speed.

And in any case the BRAS will screw me down to the nearest 500kbps..I'm
currently synching in the 4600-5300 range, but never get more than 4000
actual transfer rates.

 




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