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httpapi connect problem - routing and DNS
Sender: "Ian Patterson" <ian@xxxxxxxxxxxxxxxxxxxx>
Our problem with httpapi and dial-up PPP connections may have something to
do with routing and/or DNS issues.
Our system works on some AS/400's and not others, & we can not so far see
the difference between them (other than com adaptors/hardware etc)
This is how routing works on PPP dial-up:
A PPP session is run by a PPP profile. This must be created in Ops Nav (no
green screen commands for most of the PPP parameters).
Ops Nav/computer/Network/Remote Access Services/Originator Connection
Profiles
The PPP profile links the connection to a specific line description i.e.
'PPPLine'
It handles the connection over the modem, chap authentication for the
modems, vary on/off lines etc
The TCP settings determine the interface IP addressing.
In our case, the remote end specifies all IP addresses: local, remote, and
DNS
So the profile parameters for local and remote IP addresses are 'Assigned by
remote system'
The Routing parameter is a problem.
We can specify either: No additional routing required, Add remote system as
the default route, or Define additional static routes.
In most cases we can not use the default route option as its usually already
specified in the AS/400 routing tables
Also the remote IP addresses and the remote DNS are on different subnets.
The allocated interface addresses are 172.19.12.xx, the allocated DNS is
194.61.122.xx
So we add a static route to the PPP profile of 194.61.122.0 for the DNS
subnet.
The DNS of the PPP profile is set to dynamically assign.
When the PPP profile is activated, it gets the modem to make the call, and
then deals with the IP addressing stuff.
- remember we do not know the specific ip addresses that the remote host
will allocate, only the subnet
After the PPP profile is active, this is what we see in the active routes of
the AS/400:
Internet Network Line Interface
Opt Address Address Description Status
-- other entries removed --
172.19.12.21 172.19.12.21 GRBACSIP Active
-- other entries removed --
The GRBACSIP interface is our PPP dialup line. The interface address has
been set by the remote end as 172.19.12.21
This is the status of the associated routes of this interface address:
Route Subnet Next Route
Opt Destination Mask Hop Available
172.19.12.21 *HOST *DIRECT *YES
172.19.12.1 *HOST 172.19.12.21 *YES
194.61.122.0 255.255.255.0 172.19.12.21 *YES
224.0.0.0 240.0.0.0 *DIRECT *YES
Note that all this has been set-up automatically when the PPP profile become
active.
The remote DNS (194.61.122.x) has been linked to this interface because of
the static route in the PPP parameters.
Finally, we need an entry in the AS/400 host table for our remote server
name to an IP address (because there is no DNS available at the time (I
think - see later)
The entry is <myremoteserver.com> 172.19.12.1
As a result, when we make a call via httpapi to myremoteserver it should
find its destination via the PPP dial-up line interface.
The problem is, sometimes it doesn't work.
One possible issue is that the resolution of the servername to ip address is
not performed by the host table entry, but by some other DNS that the AS/400
accesses first.
The <myremoteserver.com> name does have an entry on the Internet (not the
one we want), but in theory the AS/400 does not have Internet access.
Does anyone have any experience of this type of PPP set-up ?
Thanks
Regards
Ian Patterson
ian@xxxxxxxxxxxxxxxxx <mailto:ian@xxxxxxxxxxxxxxxxx>
Grange IT Limited
tel 01947 880458
www.grangesystems.com
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