ISDN BRI config issue

A question is here:

2 routers are connected with BRI line. to bring up the ISDN link, which commands should use (select 3 choices):
1) Router(config-if)# encapsulation ppp
2) Router(config)# isdn switch-type <type>
3) Router(config)# dialer-list 1 protocol ip permit
4) Router(config)# dialer map <ip-address> name <name> <connection-number>
5) Router(config-if)# ip address <ip-addr> <subnet-mask>
6) Router(config-if)# dialer-group 1

Do you have any idea? I think all of them are needed. But only 3 can be selected. I need your help.
Thanks.

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Comments

tunerX

1) Router(config-if)# encapsulation ppp
2) Router(config)# isdn switch-type <type>
3) Router(config)# dialer-list 1 protocol ip permit
4) Router(config)# dialer map <ip-address> name <name> <connection-number>
5) Router(config-if)# ip address <ip-addr> <subnet-mask>
6) Router(config-if)# dialer-group 1

It all depends on the context of the question. If you mean bringing up the link to the CO then you definitely need number 2. But since there aren't two more answers that go along with bringing the link up to the CO then the question must mean connecting two routers together. I would toss this answer out.

If you do not do encapsulation ppp then both routers default to HDLC, so if you do not configure it on both routers then you do not need it. I would throw that one away as well.

You do not need to identify the interface with an IP address to bring up an ISDN call. You will definitely need an IP address or IP unnumbered address to actually send IP traffic. But the question asked about bringing up the link and not about sending traffic on the link. I would toss this one out.

You need the dialer map statement so the router will know which digits to dial to get to a particular address.

You need the dialer list statement to identify interesting traffic. Otherwise the dialer will never bring up the line to send the digits to the CO for routing.

You need the dialer group statement to associate the interface with a dialer list so the "dialer" knows which interface to bring up when interesting traffic has been identified.

I would pick answers 3, 4 and 6.

nothing_pt

As far as I recall, the minumum necessary commands are:

Router(config)# isdn switch-type switch-type
Router(config-if)# ip address <ip-addr> <subnet-mask>
Router(config)# dialer map <ip-address> name <name> <connection-number>

All others are optional or only needed with DDR.

Yankee

Turner I take the question to be for the ISDN to place a call, though I know what ya meant.

Since you can use ip unnumbered ya can eliminate the ip address...i would say you need the dialer group, the dialer list and switch type, but I don't like the question!

Yankee

kjpou1

Yankee wrote:

Turner I take the question to be for the ISDN to place a call, though I know what ya meant.

Since you can use ip unnumbered ya can eliminate the ip address...i would say you need the dialer group, the dialer list and switch type, but I don't like the question!

Yankee

I will agree with Yankee here. My view on this question would be for a test.

1) you do not need to specify this for the ISDN to come up.

2) TunerX gave all the reasons above but you definately need the switch type for the layers 1 and 2 to show active. So would have picked this one.

3) for specifying the interesting traffic. Would have picked this one.

4) Could be but the dialer map statement is an interface configuration command. So from a test taking view would not pick it at first unless I could not find two more, thinking that it was a mess up and am sure CISCO would not give a choice like this unless they made a mistake.

5) As stated above not necassary.

6) for the association with the dialer.

So here I would have picked the dialer group, dialer list and switch type because of the dialer map at the config level instead of the config-if level.

Kenneth

Quency

Kenneth, Yankee, tunerX, KPLAB, Nocturnal,

Thank you all for sharing your points and insigt.
Best!
Quency

tunerX

I missed the incorrect config for number 4. With that being the case then number 2 could work but the dialer will never place a call because there isn't any number. So you would be stuck with a good ISDN status but no "UP" link between the two routers.