Tag Archives: DHCP

31 Jan

DHCP domain-search on Juniper SRX

DHCP Option 119

In the last few years, the DHCP service in enterprises got more and more integrated into complex management and provisioning systems or became a part of the Active Directory solutions. Routers, switches, wireless controllers or other devices in such networks act as DHCP Proxy instead of DHCP Servers just sending the requests to the central server. But the feature itself is not dead! Sometimes you need to run it locally and not only provide the IP address and default gateway to the client device but also DNS servers information or domain-search parameters. The last feature is an DHCP Option 119 and I put it in “tricky, non-obvious DHCP config”, together with bunch of other DHCP options.

The central point of my home and lab networks is the Juniper SRX220H – it is quite old but the services and its performance fulfills my requirements so far. One of the services it provides is DHCP Server for some of the VLANs. I was not really missing the domain-search feature so far but decided to add it to make my work more convenient. This feature configuration is not straightforward, and there are many misleading guides about setting up this feature on different platforms or operating systems. Let me show you how it works on Juniper.

Read More →
21 Oct

Juniper error messages that says nothing

I wrote in the past that sometimes error messages are completely misleading and not connected to the problem that is blocking changes commit. Here is another example, I’m leaving it here because Google was not helpful on this 😉

I’ve been trying to configure DHCP server on SRX, firmware 12.1X46-D60.4, using the new approach that support both IPv4 and IPv6. DHCP parameters are now defined under access section

user@SRX# show access address-assignment pool LAN 
family inet {
    network 192.168.100.0/24;
    range Dynamic {
        low 192.168.100.101;
        high 192.168.100.140;
    }
    dhcp-attributes {
        maximum-lease-time 86400;
        domain-name lan;
        name-server {
            192.168.100.1;
        }
        router {
            192.168.100.1;
        }
    }
    host HOST1 {
        hardware-address d1:51:99:37:4d:79;
        ip-address 192.168.1.2;
    }
    host HOST2 {
        hardware-address 2d:f0:e2:51:74:55;
        ip-address 192.168.1.10;
    }
    host HOST3 {
        hardware-address d1:51:99:37:4d:79;
        ip-address 192.168.1.5;
    }
}

Attempt to commit the change result in error message

user@SRX# commit check 
error: Check-out failed for General authentication process (/usr/sbin/authd) without details
error: configuration check-out failed

Hmm.. yes, so the problem is…. no, that’s not the right guess.

The error message is not really helpful because the problem is that for two static assignments same MAC address was specified. Yes, error message was really helpful in this case….