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(ASCEND) Story of the day: Backup

One more from the series "A guy from eastern germany whines":

We have two P130/V.35 and want to do something very straight: Get a
leased line between them (using Primus TAs and a crossover G.703 E1
cable, just a test setup) to operate PPP routing IP, and get a failover
dialup link between the boxes as well. Cost us almost a day. Why ?

        ---> We accidentally READ the fine manual <---

If you read the manual you are convinced that the option you want for
this job is Session/Secondary= and you specify a secondary profile with
it. Now that works somewhat, but it has a bad problem: if the leased line
comes back the P130s do not even remotely think about dropping the dial
backup and going back to the leased line. They keep the dial connection
up for ever. Suicidal if you pay for call time.

Ok, tested around this some hours and finally gave up. Furthermore we
remembered that Ascend announced that the flaws with Metrics/Preferences
would be fixed in some 5.0Ai releases and officially in 6.0.0 (we ran
6.0.2 just for the questioners). So we thought we may give routing based
failover a try (something that should work on every router IMHO):

- Just defined 2 profiles to the same destination, one via leased and
  one dialed
- Set up the profiles with normal preferences (60 up, 120 down)
- Used Metric=1 and DownMetric=7 on the leased one
- Used Metric=2 and DownMetric=6 on the dial profile

According to commonsense this should work as expected. However it did not,
while the failover worked (dial line jumps in if leased one drops) it
did not fail back. The leased line never came back up as long as the dial
line was active. If the dial line drops (traffic idle) the leased one
suddenly is brought back up and everything normalizes, but as long as
anything is keeping the dial line busy it will never failback.

When will this get fixed ?

The next step was to check whether the "good" old hack of using Nailed/Mpp
as a fake backup solution works. As we already expected, it sort of
worked but was severly hosed by the fact that the P130 thinks the V.35
port is a 64kbps channel. Now this is better than the Max series who
think the Serial WAN has 0kbps. But if it indeed is 1984kbps (or the
part of this that the P130 can stand) it is totally wrong and messes
up the DBA stuff completely. Backup using Nailed/Mpp was thus impossible.

When will the Serial WAN style profiles finally have an option to set
the bandwidth explicitely ? I know they cannot be guessed, but why
can't I set them manually then ?

Again some hours later we had the odd idea to try out Session/Callback=
in direct violation to the manuals where it is written black on white
that Backup= is _NOT_ for backup to the same destination. In order to
fool the P130s about the destinations we used two different transfer
nets for the leased and dialed line. And it worked ! It worked excatly
as expected, dial dropped in on leased failure and went down after the
leased came back and the idle time went over. Now this was a partial
success, we just HATE transfer nets (thats what Cisco guys play with ;-)
and wanted it directly point-to-point. So we just tried the NONO and
what should I say: It works without transfer nets as well ! Just define
two profiles, give the dial profile as the Backup= of the leased one,
don't even remotly care about Preferences and Metrics and you are done.
Now this is even the intuitive way to set it up (what else would one
of the trial-and-error-but-never-RTFM guys try if not Backup= ?) and
our only fault was to RTFM and rule out Backup= as the straightforward
solution due to what is written there.

Conclusion: Don't believe what the manual says. Besides that Ascend
should finally fix the damn routing, so failover is possible by just
having correct metrics or preferences. And finally, if you sell a
box that says "supports Backup of a leased line with dial capacity"
then please document somewhere how to actually configure that.

Anyone @Ascend still reading ?

Andre.
-- 

Kanther-Line: PGP SSH IDEA MD5 GOST RIPE-MD160 3DES RSA FEAL32 RC4

+-o-+--------------------------------------------------------+-o-+
| o |               \\\- Brain Inside -///                   | o |
| o |                   ^^^^^^^^^^^^^^                       | o |
| o | Andre' Beck (ABPSoft) beck@ibh-dd.de XLink PoP Dresden | o |
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