Routing

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  • 1.  DHCP Relay on MX Series

    Posted 11-12-2013 08:58

    Hello,

     

    I'm working on a platform with DHCP server. I have a DHCP server connected to a MX80 PE router and a DHCP client connected to another MX80 PE router through a VRF. i put the DHCP relay configuration to each router. As you can see on the screencapture below, the "DHCP discover" frame is send by the client and this frame is correctly received by the MX80 router connected to the client. This frame is apparently send to the Router connected to the DHCP Server, however, this frame is dropped by the router and not sent to the DHCP Server. I add below the configuration extract and the results of the command "show  dhcp relay statistic routing-instance XXX".

    The Server and the DHCP Client are connected to a different VPLS. Each VPLS use an IRB to bridge into the L3VPN. On the platform, the backbone is about 10 routers. Only MX80 is used.

    DHCP SERVER ======MX80 PE Router (VPLS->IRB->VRF)=====BACKBONE MX80 (VRF)======== MX80 PE Router (VRF->IRB->VPLS)==== DHCP CLIENT.

    Thanks very much.

     

    DHCP CLIENT  - Router Configuration :

    _______________________________

     

    XXX_VPLS {
        instance-type vpls;
        vlan-id none;
        interface ge-1/1/6.0;
        interface ge-1/1/7.0;
        interface ge-1/1/8.0;
        interface ge-1/1/9.0;
        routing-interface irb.10;
        route-distinguisher 10.XX.XX.1:1041;
        vrf-target target:XXXXX:1041;
    }
    XXX_VRF {
        instance-type vrf;
        interface irb.10;
        route-distinguisher 10.XX.XX.1:2000;
        vrf-import XXX_IMPORT;
        vrf-export XXX_EXPORT;
        vrf-table-label;
        forwarding-options {
            dhcp-relay {
                server-group {
                    sp-1 {
                        10.0.1.10;
                    }
                }
                active-server-group sp-1;
                group client_test {
                    interface irb.10;
                }
            }
        }
    }

     


    xxx@ROUT_01> show dhcp relay statistics routing-instance XXX_VRF
    Packets dropped:
        Total                      0

    Messages received:
        BOOTREQUEST                4
        DHCPDECLINE                0
        DHCPDISCOVER               4
        DHCPINFORM                 0
        DHCPRELEASE                0
        DHCPREQUEST                0

    Messages sent:
        BOOTREPLY                  0
        DHCPOFFER                  0
        DHCPACK                    0
        DHCPNAK                    0
        DHCPFORCERENEW             0

     

     

     

    DHCP SERVER  - Router Configuration :

    _______________________________

     

     

    YYY_VPLS {
        instance-type vpls;
        vlan-id none;
        interface ge-1/1/5.0;
        interface ge-1/1/6.0;
        interface ge-1/1/7.0;
        interface ge-1/1/8.0;
        interface ge-1/1/9.0;
        routing-interface irb.10;
        route-distinguisher 10.XX.XX.1:1001;
        vrf-target target:XXXXX:1001;
    }
    XXX_VRF {
        instance-type vrf;
        interface irb.10;
        route-distinguisher 10.XX.XX.1:2000;
        vrf-import XXX_IMPORT;
        vrf-export XXX_EXPORT;
        vrf-table-label;
        forwarding-options {
            dhcp-relay {
                server-group {
                    sp-1 {
                        10.0.1.10;
                    }
                }
                active-server-group sp-1;
                group client_test {
                    interface irb.10;
                }
            }
        }
    }

     


    xxx@ROUT_02> show dhcp relay statistics routing-instance XXX_VRF
    Packets dropped:
        Total                      4
        Interface not configured   4

    Messages received:
        BOOTREQUEST                4
        DHCPDECLINE                0
        DHCPDISCOVER               0
        DHCPINFORM                 0
        DHCPRELEASE                0
        DHCPREQUEST                0

    Messages sent:
        BOOTREPLY                  0
        DHCPOFFER                  0
        DHCPACK                    0
        DHCPNAK                    0
        DHCPFORCERENEW             0

     

     



  • 2.  RE: DHCP Relay on MX Series

     
    Posted 11-12-2013 09:22

    Hi,

     

    I think the problem is pretty clear:

     

    "

    xxx@ROUT_02> show dhcp relay statistics routing-instance XXX_VRF Packets dropped:

        ...

        Interface not configured   4

    "

     

    so the router close to the server doesn´t see the irb as the incoming interface for the relayed DHCP-packets coming in over the VPLS.

     

    Just not sure about the right solution. I suggest to have a look at http://www.juniper.net/techpubs/en_US/junos13.2/topics/task/configuration/dhcp-subscriber-access-dhcp-relay-snooped-clients-forwarding.htmland try to get your head around the combination of conditions of your scenario. Unfortunately I´m not sure what "Actions for DHCP Relay Agent Snooped Packets When DHCP Snooping Is Disabled" is about cause I don´t get why DHCP would snoop packets when snooping is disabled ...

     

    Best Regards

     

    Ulf



  • 3.  RE: DHCP Relay on MX Series

    Posted 11-12-2013 09:50
    thanks for your answer. I'm going to read this topic.


  • 4.  RE: DHCP Relay on MX Series

    Posted 11-14-2013 02:59

    Hello Ulf,

     

    I tried the topics about the DHCP Snooping and as you said it works fine, i've add the dhcp-snoop forwarding under the forwarding options for the routing-instance concerned.

     

    Thanks again.

     

    Best regards.



  • 5.  RE: DHCP Relay on MX Series

     
    Posted 11-14-2013 03:55

    Hi,

     

    you´re welcome.

     

    Best Regards

     

    Ulf