Router filters- why?

Unanswered Question
Dec 6th, 2007

Router filters- why use them

In a normal CCM with a Country Dial Plan having been implemented you create a multiple instances of Route pattern 9.@ with different partitions - or it is in my supported system

9.@ partition - mobile

9.@ partition - local

9.@ partition - international

You then assign these partitions local, mobile, international to a CSS which is assigned to a end user- this provides the users call barring

In addition there are also route filters




Route filters also provide a call barring feature i.e User`s CSS "tells" you which route pattern to use which also has a route filter assigned to it.

e.g A user dials 9.077- UK mobile so you select Route pattern 9.@, partition mobile which your CSS can see.

within this route pattern 9.@( 9.077) is a filter called mobile which states service for exists for mobiles, pages so they call continues- so again can act as a second call barring feature

My question is why have filters as well since the discussion to deny access or not is taken at the users CSS level, also the Dial plan lists all the available mobiles, in our examples so you are not picking out certain mobiles to block anywhere since the service is set to exist in the filter

My view is to have a single 9.@ or even 9.! as a route pattern, allow all PSTN access on the device level and then use blocking routes on the users CSS to deny calls- The reason I'm saying this is that I`m reviewing an existing install with the above set up and my personal option is the blocking method - any thoughts


I have this problem too.
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allan.thomas Thu, 12/06/2007 - 06:05

Essentially there are two methods for deploying Class of Service, there is either the Traditional device CSS or Line/Device CSS.

What you are proposing is the Line/Device approach which far more scalable, and is most widely recommended.

With Traditional device CSS in a multi-site deployment it becomes necessary to have to create multiple CSS which include the partitions for each route-pattern which designates the gateway path selection for that particular site. This will have to be duplicated for each site.

However this is not the case with the Line/Device approach, this significantly reduces the number of Partions and CSSs required.

In this scenario the CSS is concatenated or combined with both the Line and Device CSS. Create your Blocked route-pattern partitions and assigned them to Line CSS, then create a single unrestricted Device CSS with includes the route-pattern partition(s) which enable the call to be routed out of the local gateway.

With this approach you only need to create an unrestricted Device CSS for each site/location.

This method is also recommended for deploying Extension Mobility. With Line/Device CSS the local gateway will always be used for external calls. This is because it is the Device CSS which specifies the route path selection and not the UDP Line CSS.

Please take time to read the section titled Building Classes of Service for Unified CM with the Line/Device Approach in the following document link. This details exactly what you are trying to achieve:-

Hope this helps.



iptuser55 Thu, 12/06/2007 - 06:23


I`m aware of the line method which I want to do and I`m happy with this however I also wish to remove the filters as well as they seem to duplicate call barring as in my example. Are there any circumstances / reasons why you would want to keep the filters?

mattcalderon Thu, 12/06/2007 - 06:41

What about numbers you don't want anybody to call such as 900 numbers? Creating a pattern to block such numbers is more time consuming than to create a route filter that blocks these types of numbers.

allan.thomas Thu, 12/06/2007 - 06:45

Route-filters are dialplan specific, therefore if you have multiple dialplans installed you will of course have separate route-patterns associated with these filters.

In this scenario route-filters provide more granularity for pattern matching.

For example, ordinarily in the days before route-filters it was pertinanent to configure several route patterns for International numbering schemes, for which interdigit timeouts can be a problem.

With a route-filter you simply create a single international partition assign it to your route pattern 9.@ together with your international route-filter.

I would recommend configuring/changing your existing route-pattern partitions for blocking based on the granularity you require for the line CSS, such as Local, Mobile, National, Intl. with the route-filters.

Then configure an unrestricted route-pattern 9.@ without a specific route-filter which is associated with your local gateway or route-list.

You do not necessarily need to keep the route-filters on the blocked patterns, however you will need to be more explicit with the pattern and also be aware of the interdigit timeout in this instance.



iptuser55 Thu, 12/06/2007 - 06:49

I can see why filter may be used to block numbers -reduce the number of partition etc but are they neded now days with teh line/device approach. Would you not block 9.0900 which is the same as the filter does with 9.@ pattern inessense. With regards to the timer you reduce it to 4/ 6 secs?

allan.thomas Thu, 12/06/2007 - 08:25

This may help you understand the significance of route-filters when it comes to pattern matching.

The following is an extract from the GB Numbering Plan, these are the National numbering scheme, there were simply too many International:-

# 0+2[03489]+XXXXXXXX


P: 2[03489] AREA-CODE


# 0+1[2-69]1+XXXXXXX


P: 1[2-69]1 AREA-CODE


# 0+11[3-8]+XXXXXXX


P: 11[3-8] AREA-CODE


# 0+1[2-9][02-9]X+XXXXXX


P: 1[2-9][02-9]X AREA-CODE


For these various Long-Distance patterns all you need to do is create a route-pattern with 9.@ and associate it with a route-filter which has a clause National-Access exists, AND, Area-Code exists, AND, Subscriber exists.

Therefore if you were using route-filters for blocking you would not need to define more explict patterns in order to cover all Long-distance numbers. Which is what you will need to do if you weren't.

All this obviously depends on how granular you require your class of service to be, as to how you define your route-patterns.



iptuser55 Thu, 01/10/2008 - 08:46

Thanks for your replies and sorry to go on

I can understand the end of digit timer though in some countries you are still effected by it, and the need to block numbers however the current the system I`m looking after has no blocked numbers- installed by someone else.


A user dials a number which via the CSS they are allowed to make, the call then proceeds to the Route Patterns and Router Filters ( RF) . Depending the partition they select a particular Route Filter to use. Within the RF the type of number local, national international exists or it does not so the type of call can be allowed or block. Am I missing something - Do you use RF to block individual numbers, should they have been blocked in Translations/ Route partition earlier based upon blocking partitions . If you can not block individual numbers using RF then why use them, is it just due to end of digit timers?. If you have reduced the end of digit timer down and why not delete RF and create the number you wish to block in a translation/ Route Pattern. What reason can you say to keep or use RF thanks.


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