Cisco DHCP & SLP Options 2

[marvhuffaker]

We have a customer who uses a Cisco Router for their DHCP. They are a Novell environment and need to push SLP options out in the DHCP packets. These are DHCP options 78 and 79.

Does anybody have any information on the correct syntax for implementing? We seem to be getting hung up on 2 things:

- Actual syntax or parameter to use
- How to implement the Mandatory/NonMandatory byte that precedes the values (1 or 0)

Thanks.

Marvin

Marvin Huffaker, MCNE

http://www.redjuju.com

 

[brianinms]

I don't know the exact answer to your question, but why don't they just run dhcp on their novel server?

 

[marvhuffaker]

I have asked the same thing due to the simplicity of performing this with Novell's DHCP. The key issue is that there are politics involved and territories to protect here..

Marvin

Marvin Huffaker, MCNE

http://www.redjuju.com

 

[brianinms]

So because of politics they chose to sacrifice end user performance .... hum great idea. However, I have searched google as well as cisco and cant find the sytax for either option.

 

[ADB100]

The DHCP service in IOS is pretty simple to configure. How do the two options get entered - hex, ascii, ip?

Andy

 

[marvhuffaker]

In NetWare's implementation, you put in decimals for the IP, check a box for Mandatory, and for the scope name you just put in the name. If there is a translation to hex, it does it behind the scenese.

On Windows, you do everything in HEX. I have seen reference to other implementations where HEX is also used. On Linux, I believe you just put in the strings, somewhat like on NetWare.

I found this link which talks about options (no syntax examples):

http://www.cisco.com/en/US/docs/net_mgmt/network_registrar/6.2/user/guide/UGB_Opts.html#wp1032274

Here is the config that was attempted, but doesn't work:

ip dhcp pool default
network 172.16.0.0 255.255.0.0
domain-name ourdomain.com
default-router 172.16.3.1
dns-server 172.16.2.35 172.16.2.145
option 78 ip 172.16.3.21
option 79 ascii "OURSCOPE"
lease infinite
!


The Option 79 was getting pushed, but the First letter was being truncated. I'm assumign this is because the 1st character should be the "Mandatory" byte.

Option 78 doesn't seem to come over at all. The doc that I referenced seem to indicate that the parameter name, not the option number, should be used.

Thanks.

Marvin Huffaker, MCNE

http://www.redjuju.com

 

[brianinms]

The answer is Cisco Tac

1 800 553 2447

 

[lerdalt]

Marv, got a couple extra docs for you to check out before calling tac.

http://www.cisco.com/univercd/cc/td.../ios120/120newft/120t/120t1/easyip2.htm#21582

For the debug command to verify on the router:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a0080094a52.shtml

One thing you might want to make certain of is in the client is configured to accept slp information from DHCP.

 

[lerdalt]

Wild. I just tried your config and took a packet trace of it. The router is pushing the information to the client. I even tried converting both the scope name and the ip address over to hex and it didn't make a difference.

Of course I'm trying this on a 2500 series router with what I'm guessing is some older code.

I'll have to dig out one of my old trace files to go though and see if there is a difference.

 

[ADB100]

It may be you need to enter them as hex:

  ip dhcp pool default
      network 172.16.0.0 255.255.0.0
      domain-name ourdomain.com
      default-router 172.16.3.1 
      dns-server 172.16.2.35 172.16.2.145 
      option 78 hex 31 37 32 2E 31 36 2E 33 2E 32 31
      option 79 hex 4F 55 52 53 43 4F 50 45
      lease infinite

It is probably worth getting a trace of a Netware DHCP server replying and then analysing it.

HTH

Andy

 

[marvhuffaker]

Thanks for your help guys, I'm going to try to get a packet trace from a Novell DHCP server and I'll post what happens. Just haven't got there yet.

Also, btw, I believe this is the equipment we are dealing with. Forgot to post that in original post.

cisco 1720
version 12.1 (I believe this is the version)

Thanks!

Marvin Huffaker, MCNE

http://www.redjuju.com

 

[lerdalt]

If you want, I can send you the trace I took from the cisco setup.

 

[marvhuffaker]

Thanks for all your help. I have done a trace from both Novell DHCP implementation as well as the CISCO one. I don't get any slp results from the Cisco trace, I get the following from Novell DHCP (Need to verify that Cisco is still configured to deploy those options - the admin may have nixed it.):

Novell DHCP (Note the IP and Scope names are different, otherwise the config and desired output are the same)
-----------------
Option: (t=78, l=5) Directory Agent Information = Static Discovery
Option: (78) Directory Agent Information
Length: 5
Value: 01C0A800EF
SLPDA Address: 192.168.0.239

Option: (t=79, l=13) Service Location Agent Scope = Mandatory Scope
Option: (79) Service Location Agent Scope
Length: 13
Value: 015245444a554a5553434f5045
Service Location Agent Scope = "REDJUJUSCOPE"

With both options, a "01" precedes the value. Then its just a simple hex conversion.

-- Andy, in your HEX example, you provide the hex conversion for each individual digit. Is that the proper syntax? All the packet traces list a HEX value of each octet (ie AC instead of 31 37 32 )




Marvin Huffaker, MCNE

http://www.redjuju.com

 

[marvhuffaker]

Guys, I got this working on Cisco based on information from the packet trace. All I had to do was provide the hex string that was being deployed correctly by the Novell DHCP and feed it back into the Cisco machine. Works great (Previous post shows the values I put back into it, note the Preceding 01 in each of them for the mandatory attribute).

Thanks again for your great help!

Marvin

Marvin Huffaker, MCNE

http://www.redjuju.com

 

[ADB100]

-- Andy, in your HEX example, you provide the hex conversion for each individual digit. Is that the proper syntax? All the packet traces list a HEX value of each octet (ie AC instead of 31 37 32 )

I think the syntax can be whatever the vendor wants it to be..... Ericsson IP Phones use Vendor Option 43 and they code it like that, I thought it might be similar. Glad you worked it out though )

Andy

 

[jwishnew]

Does anyone know how to make this work with an IPSec remote access VPN connection? Cisco routers and ASAs do not pass DHCP options to remote access VPN clients. They just pass the IP address.

How are others getting those options to the remote clients? Are they just hard coded?

Any ideas are appreciated. Thanks.