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  • Adding DHCP option 156 and option 4 to Cisco Router

    If you are using a Cisco Router as a DHCP server, you can still set it to offer option 156.

    Within the 'DHCP Pool'
    add this:
    option 156 ascii "ftpservers=192.168.1.x, country=1, language=1, layer2tagging=0, vlanid=0"

    If you want to add DHCP option 4 (SNTP time server)
    add this:
    option 4 ip 131.107.1.10 (or IP of your Time Server)

  • #2
    This just goes to show that I should check this forum more often. I ran into this issue the other day and it took me some time to get through. We had a problem for some reason with the option 4. The Cisco routher showed it was locked with a time source in Chicago and was showing Central Time (we are in Minnesota) and was in daylight savings mode, however the ShoreTel phones were 1 hour off. We eventually made an entry in the custom file for the 230 and 560 phones (sbbcustom and s6custom I think) and entered snmp 192.168.1.X or whatever your time server is and that worked too.

    Comment


    • #3
      Option 156 on a Cisco 1841 router ver 12.4

      I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


      ip dhcp pool Shoretel
      network 192.168.5.0 255.255.255.0
      default-router 192.168.5.1
      option 4 ip 192.168.0.15
      dns-server 192.168.0.5
      option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
      option 2 hex ffff.8f80

      ip dhcp excluded 192.168.5.1 192.168.7.50


      With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

      Does anyone know if the option is limited to certain routers?

      Comment


      • #4
        Originally posted by Brian
        I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


        ip dhcp pool Shoretel
        network 192.168.5.0 255.255.255.0
        default-router 192.168.5.1
        option 4 ip 192.168.0.15
        dns-server 192.168.0.5
        option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
        option 2 hex ffff.8f80

        ip dhcp excluded 192.168.5.1 192.168.7.50


        With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

        Does anyone know if the option is limited to certain routers?
        You are putting the phones into VLAN 0 which is probably not configured... What VLAN are your phones supposed to be in? You have also turned off layer 2 tagging which you should keep on if you are using VLANs.

        Comment


        • #5
          Originally posted by Charles
          If you are using a Cisco Router as a DHCP server, you can still set it to offer option 156.

          Within the 'DHCP Pool'
          add this:
          option 156 ascii "ftpservers=192.168.1.x, country=1, language=1, layer2tagging=0, vlanid=0"

          If you want to add DHCP option 4 (SNTP time server)
          add this:
          option 4 ip 131.107.1.10 (or IP of your Time Server)
          If you are not using VLANs I believe you should set the vlanid to 1 which is the default vlan in cisco....

          Comment


          • #6
            Your could try adding the older 66 option for the ip 100 and dropping the 156 if you don't need vlan tagging.

            option 66 ascii "192.168.1.10" would be the format. I know it still worked for the 530/560/110 under 6.0. I never tried it with a 230. But that does not mean they will support it forever.

            As for the option 156 I don't think 0 is the null value. It may be "null" or just nothing at all. You might try play around with different values for null.
            Last edited by aspen; 02-22-2007, 01:49 PM.
            There are 10 types of people in the world, those that understand binary and those that donít.

            Comment


            • #7
              Could it be the dhcp excluded statement? Is that a range or list? why the 7?

              Comment


              • #8
                Originally posted by tnshurtm
                Could it be the dhcp excluded statement? Is that a range or list? why the 7?
                That's a good eye...

                ip dhcp excluded 192.168.5.1 192.168.7.50

                this would exclude the entire 192.168.5.1 - 192.168.7.50 RANGE from being issued.

                Originally posted by Cisco
                Issue the ip dhcp excluded-address command to exclude IP
                !--- addresses from being assigned by the DHCP server.
                Wonder if it's just a typo.

                Charles

                Comment


                • #9
                  Found a solution

                  Originally posted by Brian
                  I'm installing a similar configuration from posts on this forum about using DHCP on a Cisco router....


                  ip dhcp pool Shoretel
                  network 192.168.5.0 255.255.255.0
                  default-router 192.168.5.1
                  option 4 ip 192.168.0.15
                  dns-server 192.168.0.5
                  option 156 ascii "ftpservers=192.168.0.15, country=1, language=1, layer2tagging=0,vlanid=0"
                  option 2 hex ffff.8f80

                  ip dhcp excluded 192.168.5.1 192.168.7.50


                  With option 156 in the configuration, DHCP doesn't work and the phones do not recieve an IP until I remove it from the configuration.

                  Does anyone know if the option is limited to certain routers?
                  I found that the small Cisco 1700 router I was trying to configure for DHCP could not handle all of those lines. I removed "option 2 hex ffff.8f80" and it worked like a charm... I'm thinking it had to do with placing too much on the router to issue out all of those lines...

                  Thanks for all of the great suggests. I hope this helps some one else.

                  Comment


                  • #10
                    Option 4 or Option 42

                    Is there a difference in option 4 and option 42. I have always used 42, as i was looking for an actual NTP. Advice?

                    Comment

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