From: Nauman Khan (mustafa@247emails.com)
Date: Sun Jan 25 2004 - 01:08:15 GMT-3
--- Nauman Mustafa <nmustafa@cisco.com> wrote:
phase90 wrote:
>Nauman & Jay,
>
> Does this mean that if you were to look at the debug q921 or
>q931 output of ISDN control plane you would see the other SPID # appear in setup messages
>even though it is not configured in the router?
>
Hi Jerry,
IMHO, the router always starts trying to dial the numbers specified by dial string under the bri interface...from top to bottom in order of appearance.
Consider these 2 scenarios:
1. You get 2 spids from telco and you have p2p connection b/w calling and called router.
Router A----------<>--------RouterB
Lets say you want to bring the second B channel up once the load-threshold crosses 20
then you will have on router A
int brix/y
ip address .........
dialer string xxxx
dialar string yyyy
dialer load-threshold 20
--rest of the config--
In this case, when router A gets interesting traffic, it bring up first B channel
Now, when the load threshold crosses 20, the router will dial the number speciied in the first "dialer string"
under the bri interface. So in this case , it will dial xxxx, it will get a busy since the first B channel is up.
Then it will dial the number in the dialer string command ,which is yyyy and will bring the B channel up.
Now, in the scenario, where you only get one spid, from Telco , it normally means, that Telco has setup hunt group or
automatic rollover on their side.Please refer to my previous post on this topic on how automatic rollover works.
So in this case you have one number or dial string that you configure on your calling router to dial the remote router.
So your above config will look like this:
int brix/y
ip address .........
dialer string xxxx
dialer load-threshold 20
--rest of the config--
In this secnario, when the load threshold crosses 20, the router will still dial xxxx. It will get a busy but since
the switch is configure for automatic rollover, it will hunt to the second channel and will bring up the second B channel.
So the two b channels can be brought up using only one single string and is normally the case when Telco provide you with
only one spid.
As far as the ccie lab is concerned, I would just configure whatever is given to us.
If they only give one spid, then their isdn switch either should be configured for rollover or they shouldnt be asking us
to bring up the second channel up.
....just my 2 cents.
Best Regards,
-Nauman
>
>
>Jerry
>----- Original Message -----
>From: "Nauman Khan" <mustafa@247emails.com>
>To: "Jay Hennigan" <jay@west.net>; "Nauman Khan" <mustafa@247emails.com>
>Cc: "Yasser Aly" <blackyeyes00@hotmail.com>; <ccielab@groupstudy.com>
>Sent: Saturday, January 24, 2004 4:18 AM
>Subject: Re: ISDN Multilink ( Problem to bring 2nd channel up )
>
>
>
>
>>Jay Hennigan wrote:
>>
>>
>>
>>>I believe you are wrong, but this may be one of those "it depends" type
>>>of things. SPIDs are layer 2 communication between the ISDN TE and the
>>>switch, related to the actual raw B channel. If the switch requires a
>>>spid for one channel, it will require it for the other as well. Note
>>>that the real world may vary from a simulator and from the specific lab
>>>environment.
>>>
>>>
>>Hi Jay,
>>
>>Thanks for correcting me.
>>I also think I am wrong when I say that:
>>
>>
>>
>>>You would need the second spid numbers if you want to bring the second
>>>
>>>
>>channel up without considering load threshold. If you only specify one
>>spid, then the second channel will only come up once your configured >load
>>
>>
>threshold is corssed. (Somebody can correct me if I am wrong)
>
>
>>which then means, that the only way to bring the second channel up is the
>>
>>
>use of dialer load-threshold command ?
>
>
>>but I was just trying to find out why we would ever need to specify
>>2 spids, as Yasser asked. The only time I have seen 2 spid's needing to be
>>
>>
>specified (in real world) is when using a bas-ni switch type.
>
>
>>Although it works with one spid too... (depending on how switch is setup
>>from the telco side)
>>
>>Regarding your following comments:
>>
>>
>>
>>>SPIDs are layer 2 communication between the ISDN TE and the
>>>switch, related to the actual raw B channel. If the switch requires a
>>>spid for one channel, it will require it for the other as well. Note
>>>that the real world may vary from a simulator and from the specific lab
>>>environment.
>>>
>>>
>>Its not necessary (in real world configuration) to have 2 spids to bring
>>
>>
>up the second channel.
>
>
>>For e.g. in DMS100 switch case, generally telco gives you only 1 spid
>>
>>
>number. But that does not mean you have only one spid. You still dial out on
>2 channels.
>
>
>>The way it works is there is a thing called automatic rollover or B
>>
>>
>channel hunt group that Telco configures on their switch. No router
>configuration involved.
>
>
>>What it does is when we dial xxx string (which lets say is the only string
>>
>>
>that we got from Telco), it connects on first B channel. Now when router has
>to bring up 2nd channel, it again tries xxx string, and since telco has both
>b channels in one single hunt group or in automatic rollover,you will
>connect on 2nd channel with the same xxx string.
>
>
>>This is alternate to have multiple dial strings on the source router for
>>
>>
>each B channel.
>
>
>>Cheers,
>>
>>Nauman
>>
>>
>>
>>
>>_____________________________________________________________
>>Join www.247emails.com today for a FREE email account. Upgrade to our
>>
>>
>mailplus program and RECIEVE a FREE Gift pack which includes 50 PSD website
>templates, lot s of useful ebooks with resale rights...
>
>
>>www.247emails.com
>>
>>_______________________________________________________________________
>>Please help support GroupStudy by purchasing your study materials from:
>>http://shop.groupstudy.com
>>
>>Subscription information may be found at:
>>http://www.groupstudy.com/list/CCIELab.html
>>
>>
>
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>http://shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
>
>
This archive was generated by hypermail 2.1.4 : Mon Feb 02 2004 - 09:07:50 GMT-3