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I'm trying to configure a basic DHCP server on a Juniper MX5. Although I have a significant experience of configuring DHCP servers on a branch Juniper devices, the standard approach mysteriously doesn't work: as soon as I switch to DHCP on a client host, the connectivity breaks, the only protocol that is working is ARP (the host even cannot ping a router). The most astonishing aspect is that I assign the same IPv4 address as static as the MX5 gives as dynamic, yet when received by DHCP it doesn't work.

I've found a book where it's explained how to configure DHCP on a high-end JunOS devices using vlan-ranges, dynamic profiles and bound variables; is this even possible without all of this ?

I'm using the following config:

[access]
profile local {
    authentication-order none;
}
address-assignment {
    pool vlan116v6 {
        family inet6 {
            prefix 2a04:8681::/64;
            dhcp-attributes {
                dns-server {
                    2001:4860:4860::8844;
                    2001:4860:4860::8888;
                }
            }
        }
    }
    pool vlan116v4 {
        family inet {
            network 10.10.116.0/24;
            range vlan116-dynamic {
                low 10.10.116.51;
                high 10.10.116.249;
            }
            dhcp-attributes {
                domain-name hosting-telecom.uk;
                name-server {
                    8.8.4.4;
                    8.8.8.8;
                }
                router {
                    10.10.116.1;
                }
            }
        }
    }
}
[system services]
ssh;
dhcp-local-server {
    dhcpv6 {
        overrides {
            interface-client-limit 100;
        }
        group vlan116 {
            interface irb.116;
        }
    }
    pool-match-order {
        ip-address-first;
    }
    authentication {
        username-include {
            mac-address;
        }
    }
    group default {
        interface irb.116;
    }
}
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1 Answer 1

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2

It look you're missing the binding between the dhcp-local-server group and the access-profile which links to the address-assignment.

Try:

set system services dhcp-local-server group default access-profile local
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2
  • Yeah, thanks, it's really missing. Although adding this logical connection didn't help. I fully realize that my post looks like "some guy is posting fairy tales on the internet", but I double- and triplechecked the settings - ip/masks/gw are correct. I've even wiresherked the dhcp client machine - nothing is working except ARP: every other frame is just sent without answer. I requested a working MX DHCP config from a friend of mine working at ISP, and got it, but it's hugely integrated with radius and requires the whole network scheme rebuild, since it's done with flexible vlan tagging etc.
    – drookie
    Commented Dec 9 at 5:57
  • Try removing the authentication stanza from dhcp-local-server and see if anything changes. Not sure why you’d need this if you’re not doing subscriber interfaces.
    – Benjamin Dale
    Commented Dec 10 at 8:31

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