Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

DNS - Router s NSAP & Hostname Resolution

Hi all,

My Connectivity is like below

DNS->CS->BBR->(NIB)->AR->ER

Where between DNS & ER Router all other Routers are there,

i have not given first mentioned DNS in BBR,

cant do ping hostname in AR, BBR ( could i have to give DNS in BBR)

but can do ping hostname to the device connected to CS

-----------

i have given the below configuration

ip subnet-zero

ip name-server 10.194.208.180

ip name-server 10.194.208.179

ip domain lookup

ip domain-name wdc.bsnl.co.in

could i have to give the below also

access-list 10 permit udp any any eq domain

access-list 10 permit udp any eq domain any

access-list 10 deny any

The configuration related to NSAP is as below

I have added two entries in DNS server

for loopback0(Hostanme of Router) &

for Loopback1(NSAP Address-75505017550014) which is mentioned below

X25 route has given for this to come inside Network from Remote

Nsap address on the remote side is 75505017550014

Nsap address on the Inside network is 20405017550002

The Problem is i have to get ping nsap Successful from that router

x25 route 75505017550014 interface Serial0/1/1

x25 route 20405017550002 xot z.z.z.z xot-source Loopback0

interface Serial0/1/1

no ip address

encapsulation x25 dce

clock rate 64000

interface Loopback0

description "LOOPBACK-0"

ip address x.x.x.x 255.255.255.255

interface Loopback1

description "LOOPBACK-1"

ip address y.y.y.y 255.255.255.255

13 REPLIES
Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Hello Anand,

I see this is a continuation of your previous thread here.

You have indicated that you have put the NSAP addresses into DNS. Yet you have asked me what should be the name of the NSAP endpoint to use. This is contradictory - if you have indeed inserted the NSAP addresses into the DNS you would also assign names to them and you would not be asking me about them at all. Therefore, please, can you post here the records you have inserted into the DNS precisely as you have inserted them - the complete DNS resource records including their name, type and value? No just description please - we need to see those resource records from your DNS in detail.

Also you did not answer my previous question clearly: can you ping the remote endpoint when you ping its NSAP address instead of pinging it by name?

Best regards,

Peter

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Dear Peter,

ping nsap address(75505017550014) is not successful in ER , but primarily the issue is in AR itself the ping Hostanme is not happening i m posting it for your reference

Other Query is there that,

My Connectivity is like below

DNS->CS->BBR->(NIB)->AR->ER

Where between DNS & ER Router all other Routers are there,

i have not given first mentioned DNS in BBR,

cant do ping hostname in AR, BBR ( could i have to give DNS in BBR)

but can do ping hostname to the device connected to CS

how can i resolve this

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Dear Anand,

I am sorry but I am still struggling to understand your description. Copying the same text over again does not help me. Can you explain those acronyms - CS, BBR, NIB, AR, ER for me? What does it mean when the arrow points from the Domain Name Service server towards the CS?

Also it would be useful if you could post the transcript of the ping command that was not successful exactly as it appears in your terminal. Because I am still at loss what experiments you are doing to determine the functionality, seeing the command will provide me with a hint.

And please - post those DNS records I have asked in my previous post.

Best regards,

Peter

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Extended ping to DNS from AR is OK

AR HostName#ping AR HostName

Translating "AR HostName"...domain server (10.194.208.179) (10.194.208.180)

% Unrecognized host or address, or protocol not running.

&The Notation is like this

BBR-Backbone Router

CS-Core Switch

AR-Aggregation Router

ER-router

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Hello Anand,

Okay, it's fine that the DNS can be pinged from the AR.

You are trying to ask the DNS server using the ping command for the NSAP address. I'm not quite sure now if it will work this way.

However, there is the command "x28". It can be used to retrieve the X25 resource records from the DNS. Try it to see if the DNS responds to you with the requested translation.

In the privileged mode, simply enter the command "x28" and hit Enter. You will be placed in a new shell. There, on the new line, simply write the name you want to look up in the DNS. The x28 shell can be terminated using the "exit" command. See this URL for more details:

http://www.cisco.com/en/US/docs/ios/wan/configuration/guide/wan_cfg_x25_lapb_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1003090

Again, I would like to ask you if you have indeed inserted X25 or NSAP addresses in the DNS and how do the respective resource records look like.

Best regards,

Peter

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Dear Peter,

We have given two DNS entries for this in DNS server as like below

Hostname of Router IN A 10.80.0.1

79000024130000 IN A 10.72.20.38

then why couldnt the ping nsap happen

below error is notified when checking x28 shell command

*75505017550014

% pad connections not permitted from this terminal

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Hello Anand,

Well, in your DNS, you have created a translation record to an IPv4 address. This was the clue I have been asking for three times :)

But you want to get an NSAP address out of the DNS. The record should look as follows:

Router_A_Hostname IN X25 79000024130000

assuming that the 79000024130000 is the NSAP address of the Router A.

Best regards,

Peter

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Dear Peter,

Padon me that two enties have to be taken from other team

So two entries like below has to be given

Hostname_Router_A IN A Router_A_IP address

Router_A_Hostname IN X25 79000024130000

but X25 has to be raplaced in the default place of Alias in entries of DNS

other problem is that i could not get ping hostname in AR

Thanks

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Hello Anand,

That DNS configuration looks much better.

I don't understand this statement: "but X25 has to be raplaced in the default place of Alias in entries of DNS". Can you reformulate it?

Regarding the fact that you can't ping the AR's hostname - note that the DNS appends a domain to every unqualified (not terminated with a dot character) name in its configuration. Can you confirm from a PC connected to the DNS that the AR's hostname can be resolved with a proper domain? Try pinging the AR with the full domain name terminated by the dot, like: ping ar.wdc.bsnl.co.in. including the trailing dot.

Best regards,

Peter

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Dear peter,

in dns entries are given like this

hostname IN X25 75505017550014

hostname IN A 10.100.0.9

in Router, below configuration is given

x25 routing

service pad to-xot

service pad from-xot

ip domain-list google.com

x25 route 75505017550014 dns \0

i followed the below link for this configuration

http://www.cisco.com/en/US/docs/ios/12_0t/12_0t5/feature/guide/x25dns.html

apart if dns is not given in BBR and we are checking dns through AR , is it possible it works

the pc connected to dns d oes resolve hostname of AR& the ping ar.fqdn from pc does happen

could u help me out

New Member

Re: DNS - Router s NSAP & Hostname Resolution

Dear Peter,

what could be the Problem,

i m struck on with this , can u help me out

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Dear Anand,

I have went over your posts here once again, I've gone through the documentation and I have realized I have been mistaken in a couple of instances. I am sorry for that - let's try to correct my mistakes here.

Without referring to your particular topology, consider having two routers, R1=1.1.1.1 and R2=2.2.2.2, connected by an ISP. You want to run the XOT between these two and let us demonstrate everything on this topology.

First of all, the addresses used in X.25 are not NSAP, but rather X.121 addresses, so let's refer to them under this name. Let the R1's X.121 address be 91111111110001 and the R2's X.121 address be 92222222220002.

Regarding the DNS: You do not need the DNS for running XOT between your two routers. You can set the XOT completely statically as you did the first time and I suggest doing just that for now.

On R1:

service pad to-xot

service pad from-xot

x25 routing

x25 route 92222222220002 xot 2.2.2.2

x25 host R1 91111111110001

x25 host R2 92222222220002

On R2:

service pad to-xot

service pad from-xot

x25 routing

x25 route 91111111110001 xot 1.1.1.1

x25 host R1 91111111110001

x25 host R2 92222222220002

Note the "x25 host" lines. They assign the X.121 address both to the local host and to the remote host. Each router assigns an X.121 address to itself, and also it contains a translation for the second router. Now, if the "pad" transport is allowed on the "line vty 0 4" on R2 (using the command "transport input all" or "transport input ssh pad"), you should be able to access the R2's command line from R1 using the PAD service as follows:

R1#pad 92222222220002

Trying 92222222220002...Open

R2>exit

[Connection to 92222222220002 closed by foreign host]

R1#pad R2

Trying 92222222220002...Open

R2>exit

[Connection to R2 closed by foreign host]

R1#

In my examples here, I have used the "no login" on the R2 VTYs, that's why it does not require a username/password when logging in.

This way, you can confirm whether your XOT is working between your two routers. Can you try to replicate this for your particular names and X.121/IP addressing?

Regarding the DNS: I have suggested wrong entries for it. I apologize. If I wanted to make it correctly for the example network I have suggested here, the DNS would contain these entries:

R1 IN X25 91111111110001 ; The R1's name and corresponding X.121 address

R2 IN X25 92222222220002 ; The R2's name and corresponding X.121 address

91111111110001 IN A 1.1.1.1 ; The R1's X.121 and corresponding IP for XOT

92222222220002 IN A 2.2.2.2 ; The R2's X.121 and corresponding IP for XOT

The configuration of the routers would need in turn to be modified: the static X25/XOT routes would need to be removed as well as all the "x25 host" commands. Instead of those, this lines would need to be inserted:

On R1:

x25 route R2 xot dns \0

On R2:

x25 route R1 xot dns \0

Let me stress once more that the DNS introduces a large possibility of errors (maintaining a well-behaved DNS is an arduous task by itself) and that for this simple scenario, I strongly discourage you from using it.

Also, it seems that the PING will not work here to test the X.25/XOT connectivity. The X.25/LAPB is not among the protocols supported by the PING command. Use the "pad" command to test the connectivity.

Best regards,

Peter

Cisco Employee

Re: DNS - Router s NSAP & Hostname Resolution

Hello Anand,

Is there anything new regarding your issue?

Best regards,

Peter

786
Views
3
Helpful
13
Replies